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Cisco IOS IP Addressing Services Command Reference
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accounting DHCP through clear ip route
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clear ip route dhcp through ip arp entry learn
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ip arp gratuitous through ip dhcp ping packets
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ip dhcp ping timeout through ip dhcp-client forcerenew
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ip dhcp-client network-discovery through ip nat sip-sbc
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ip nat source through iterate-ip-addrs
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lease through renew dhcp
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reserved-only through show ip irdp
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show ip masks through vrf DHCP pool
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Index
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Feedback
Contents
lease through renew dhcp
- lease
- local-ip (IPC transport-SCTP local)
- local-port
- logging (cfg-dns-view)
- logging (DNS)
- logging server-arp
- mac packet-classify
- mac packet-classify use vlan
- match message-type
- match reply prefix-list
- match server access-list
- match service-instance
- match service-type
- mode (nat64)
- name
- nat64 enable
- nat64 logging
- nat64 logging translations
- nat64 map-t
- nat64 prefix stateful
- nat64 prefix stateless
- nat64 route
- nat64 service ftp
- nat64 settings
- nat64 settings eif
- nat64 settings flow-entries disable
- nat64 settings mtu minimum
- nat64 switchover replicate http
- nat64 translation
- nat64 v4
- nat64 v4v6
- nat64 v6v4
- netbios-name-server
- netbios-node-type
- network (DHCP)
- next-server
- nhrp group
- nhrp map group
- nis address
- nis domain-name
- nisp domain-name
- nisp address
- odap client
- odap server
- option
- option hex
- option ext
- origin
- override default-router
- override utilization high
- override utilization low
- port-parameters
- preempt
- preference (DHCPv6 Guard)
- prefix-delegation
- prefix-delegation aaa
- prefix-delegation pool
- priority (firewall)
- protocol
- rbe nasip
- redundancy
- redundancy asymmetric-routing enable
- redundancy group
- redundancy group (interface)
- relay agent information
- relay destination
- relay source
- relay target
- relay-information hex
- release dhcp
- remote command
- remote login
- remote-ip (IPC transport-SCTP remote)
- remote-port
- remote-span
- renew deny unknown
- renew dhcp
lease
To configure the duration of the lease for an IP address that is assigned from a Cisco IOS Dynamic Host Configuration Protocol (DHCP) server to a DHCP client, use the lease command in DHCP pool configuration mode. To restore the default value, use the no form of this command.
Syntax Description
days
Specifies the duration of the lease in numbers of days.
hours
(Optional) Specifies the number of hours in the lease. A days value must be supplied before you can configure an hours value.
minutes
(Optional) Specifies the number of minutes in the lease. A days value and an hours value must be supplied before you can configure a minutes value.
infinite
Specifies that the duration of the lease is unlimited.
Command History
Release
Modification
12.0(1)T
This command was introduced.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2SX
This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.
local-ip (IPC transport-SCTP local)
To define at least one local IP address that is used to communicate with the local peer, use the local-ipcommand in IPC transport-SCTP local configuration mode. To remove one or all IP addresses from your configuration, use the no form of this command.
local-ip device-real-ip-address [device-real-ip-address2]
no local-ip device-real-ip-address [device-real-ip-address2]
Syntax Description
device-real-ip-address
IP address of the local device.
The local IP addresses must match the remote IP addresses on the peer router. There can be either one or two IP addresses, which must be in global Virtual Private Network (VPN) routing and forwarding (VRF). A virtual IP (VIP) address cannot be used.
device-real-ip-address2
(Optional) IP address of the local device.
Usage Guidelines
Use the local-ip command to help associate Stream Control Transmission Protocol (SCTP) as the transport protocol between the local and remote peer.
This command is part of a suite of commands used to configure the Stateful Switchover (SSO) protocol. SSO is necessary for IP Security (IPSec) and Internet Key Exchange (IKE) to learn about the redundancy state of the network and to synchronize their internal application state with their redundant peers.
local-port
To define the local Stream Control Transmission Protocol (SCTP) port that is used to communicate with the redundant peer, use the local-portcommand in SCTP protocol configuration mode.
Usage Guidelines
The local-port command enters IPC transport-SCTP local configuration mode, which allows you to specify at least one local IP address (via the local-ip command) that is used to communicate with the redundant peer.
logging (cfg-dns-view)
To enable logging of a system message logging (syslog) message each time the Domain Name System (DNS) view is used, use the logging command in DNS view configuration mode. To disable logging of a syslog message each time the DNS view is used, use the no form of this command.
Usage Guidelines
This command enables the logging of syslog messages for the DNS view.
To display the logging setting for a DNS view, use the show ip dns view command.
Examples
The following example shows how to enable logging of a syslog message each time the DNS view named user3 that is associated with the VRF vpn32 is used:
Router(config)# ip dns view vrf vpn32 user3 Router(cfg-dns-view)# loggingRelated Commands
Command
Description
ip dns view
Enters DNS view configuration mode for the specified DNS view so that the logging setting, forwarding parameters, and resolving parameters can be configured for the view.
show ip dns view
Displays information about a particular DNS view or about all configured DNS views, including the number of times the DNS view was used.
logging (DNS)
To enable logging of a system message logging (syslog) message each time the Domain Name System (DNS) view is used, use the logging command in DNS view configuration mode. To disable logging of a syslog message each time the DNS view is used, use the no form of this command.
Usage Guidelines
This command enables the logging of syslog messages for the DNS view.
To display the logging setting for a DNS view, use the show ip dns view command.
Examples
The following example shows how to enable logging of a syslog message each time the DNS view named user3 that is associated with the VRF vpn32 is used:
Router(config)# ip dns view vrf vpn32 user3 Router(cfg-dns-view)# loggingRelated Commands
Command
Description
ip dns view
Enters DNS view configuration mode for the specified DNS view so that the logging setting, forwarding parameters, and resolving parameters can be configured for the view.
show ip dns view
Displays information about a particular DNS view or about all configured DNS views, including the number of times the DNS view was used.
logging server-arp
To enable the sending of Address Resolution Protocol (ARP) requests for syslog server address during system initialization bootup, use the logging server-arp command in global configuration mode. To disable the sending of ARP requests for syslog server addresses, use the no form of this command.
Usage Guidelines
The logging server-arp global configuration command allows the sending of ARP requests for syslog server addresses during system initialization bootup.
When this CLI command is configured and saved to the startup configuration file, the system will send an ARP request for remote syslog server address before sending out the first syslog message.
The command should only be used when the remote syslog server is in the same subnet as the system router sending the ARP request.
NoteUse this command even if a static ARP has been configured with the remote syslog server address.
Examples
The following example shows how to enable an ARP request for syslog server addresses:
Router# configure terminal Router(config)# logging server-arp Router(config)# exitThe following example shows how to disable an ARP request for syslog server addresses:
Router# configure terminal Router(config)# no logging server-arp Router(config)# exitmac packet-classify
To classify Layer 3 packets as Layer 2 packets, use the mac packet-classify command in interface configuration mode. To return to the default settings, use the no form of this command.
Usage Guidelines
This command is not supported on Cisco 7600 series routers that are configured with a Supervisor Engine 2.
You can configure these interface types for multilayer MAC access control list (ACL) quality of service (QoS) filtering:
- VLAN interfaces without Layer 3 addresses
- Physical LAN ports that are configured to support Ethernet over Multiprotocol Label Switching (EoMPLS)
- Logical LAN subinterfaces that are configured to support EoMPLS
The ingress traffic that is permitted or denied by a MAC ACL on an interface configured for multilayer MAC ACL QoS filtering is processed by egress interfaces as MAC-layer traffic. You cannot apply egress IP ACLs to traffic that was permitted or denied by a MAC ACL on an interface configured for multilayer MAC ACL QoS filtering.
Microflow policing does not work on interfaces that have the mac packet-classify command enabled.
The mac packet-classify command causes the Layer 3 packets to be classified as Layer 2 packets and disables IP classification.
Traffic is classified based on 802.1Q class of service (CoS), trunk VLAN, EtherType, and MAC addresses.
Examples
This example shows how to classify incoming and outgoing Layer 3 packets as Layer 2 packets:
Router(config-if)# mac packet-classify Router(config-if)#This example shows how to disable the classification of incoming and outgoing Layer 3 packets as Layer 2 packets:
Router(config-if)# no mac packet-classify Router(config-if)#This example shows how to enforce Layer 2 policies on BPDU packets:
Router(config-if)# mac packet-classify bpdu Router(config-if)#This example shows how to disable Layer 2 policies on BPDU packets:
Router(config-if)# no mac packet-classify bpdu Router(config-if)#mac packet-classify use vlan
To enable VLAN-based quality of service (QoS) filtering in the MAC access control lists (ACLs), use the mac packet-classify use vlan command in global configuration mode. To return to the default settings, use the no form of this command.
Usage Guidelines
This command is supported in PFC3BXL or PFC3B mode only.
This command is not supported on Cisco 7600 series routers that are configured with a Supervisor Engine 2.
You must use the no mac packet-classify use vlan command to disable the VLAN field in the Layer 2 key if you want to apply QoS to the Layer 2 Service Advertising Protocol (SAP)-encoded packets (for example, Intermediate System-to-Intermediate System [IS-IS] and Internet Packet Exchange [IPX]).
QoS does not allow policing of non-Advanced Research Protocol Agency (ARPA) Layer 2 packets (for example, IS-IS and IPX) if the VLAN field is enabled.
match message-type
To configure parameters for a service-list based on a message type, use the match message-type command in multicast Domain Name System (mDNS) service discovery service-list mode. To disable configuration of parameters for a service-list based on a message type, use the no form of this command.
Usage Guidelines
The match message-type command must be used after a service-list is created, and the permit or deny option is exercised.
Examples
The following example shows how to filter a service-list for the announcement message type.:
Device> enable Device# configure terminal Device(config)# service-list mdns-sd sl1 permit 3 Device(config-mdns-sd-sl)# match message-type announcement Device(config-mdns-sd-sl)# exitRelated Commands
Command
Description
service-list mdns-sd
Creates a service-list and applies a filter on the service-list or associates a query for the service-list.
match service-instance
Configures parameters for a service-list, for a specified service-instance.
match service-type
Configures parameters for a service-list, for a specified service-type.
show mdns statistics
Displays mDNS statistics for the specified service-list.
match reply prefix-list
To enable verification of the advertised prefixes in the Dynamic Host Configuration Protocol (DHCP) reply messages from the configured authorized prefix list, use the match reply prefix-list command in DHCPv6 guard configuration mode. To disable verification of the advertised prefixes in the DHCP reply messages from the configured authorized prefix list, use the no form of this command.
Command Default
The advertised prefixes in DHCP reply messages from the configured authorized prefix list are not verified.
Usage Guidelines
This command enables verification of the advertised prefixes in DHCP reply messages from the configured authorized prefix list. If not configured, this check will be bypassed. A prefix list is configured using the ipv6 prefix-list command. An empty prefix list is treated as a permit.
Examples
The following example defines a DHCPv6 guard policy name as policy1, places the router in DHCPv6 guard configuration mode, and enables verification of the advertised prefixes in DHCP reply messages from the configured authorized prefix list:
Router(config)# ipv6 dhcp guard policy policy1 Router(config-dhcp-guard)# match reply prefix-list ipv6pre1match server access-list
To enable verification of the advertised Dynamic Host Configuration Protocol (DHCP) server or relay address in inspected messages from the configured authorized server access list, use the match server access-list command in DHCPv6 guard configuration mode. To disable verification of the advertised DHCP server or relay address in inspected messages from the configured authorized server access list, use the no form of this command.
Command Default
The advertised DHCP server or relay address in inspected messages from the configured authorized server access list are not verified.
Usage Guidelines
Enables verification of the advertised DHCP server or relay address in inspected messages from the configured authorized server access list. If not configured, this check will be bypassed. An access list is configured using the ipv6 access-list command. An empty access list is treated as a permit. The access list is configured using the ipv6 access-list command.
Examples
The following example defines a DHCPv6 guard policy name as policy1, places the router in DHCPv6 guard configuration mode, and enables verification of the advertised DHCP server or relay address in inspected messages from the configured authorized server access list:
Router(config)# ipv6 dhcp guard policy policy1 Router(config-dhcp-guard)# match server access-list ipv6acl1match service-instance
To configure parameters for a service-list based on a service-instance, use the match service-instance command in multicast Domain Name System (mDNS) service discovery service-list mode. To disable configuration of parameters for a service-list based on a service-instance, use the no form of this command.
Usage Guidelines
The match service-instance command must be used after a service-list is created, and the permit or deny option is exercised.
Examples
The following example shows how to filter a service-list by a service instance:
Device> enable Device# configure terminal Device(config)# service-list mdns-sd sl1 permit 3 Device(config-mdns-sd-sl)# match service-instance service1 Device(config-mdns-sd-sl)# exitRelated Commands
Command
Description
service-list mdns-sd
Creates a service-list and applies a filter on the service-list or associates a query for the service-list.
match message-type
Configures parameters for a service-list, for a message-type.
match service-type
Configures parameters for a service-list, for a specified service-type.
show mdns statistics
Displays mDNS statistics for the specified service-list.
match service-type
To configure parameters for a service-list based on a service-type, use the match service-type command in multicast Domain Name System (mDNS) service discovery service-list mode. To disable configuration of parameters for a service-list based on a service-type, use the no form of this command.
Usage Guidelines
The match service-type command must be used after a service-list is created, and the permit or deny option is exercised.
Examples
The following example shows how to filter a service-list for a TXT service-type:
Device> enable Device# configure terminal Device(config)# service-list mdns-sd sl1 permit 3 Device(config-mdns-sd-sl)# match service-type TXT Device(config-mdns-sd-sl)# exitRelated Commands
Command
Description
service-list mdns-sd
Creates a service-list and applies a filter on the service-list or associates a query for the service-list.
match service-instance
Configures parameters for a service-list, for a service-instance.
match message-type
Configures parameters for a service-list, for a message-type.
show mdns statistics
Displays mDNS statistics for the specified service-list.
mode (nat64)
To configure the Network Address Translation 64 (NAT64) mapping of addresses and ports (MAP-T) mode, use the mode command in NAT64 MAP-T configuration mode. To exit from the NAT64 MAP-T mode, use the no form of this command.
Usage Guidelines
MAP-T or Mapping of address and port (MAP) double stateless translation-based solution (MAP-T) provides IPv4 hosts connectivity to and across an IPv6 domain. MAP-T builds on existing stateless IPv4/IPv6 address translation techniques that are specified in RFC 6052, RFC 6144, and RFC 6145.
In dual translation mode, IPv4 is translated into IPv6 and vice versa.
name
To configure the redundancy group with a name, use the namecommand in redundancy application group configuration mode. To remove the name of a redundancy group, use the no form of this command.
nat64 enable
To enable Network Address Translation 64 (NAT64) on an interface, use the nat64 enable command in interface configuration mode. To disable the NAT64 configuration on an interface, use the no form of this command.
nat64 logging
To enable Network Address Translation 64 (NAT64) high-speed logging (HSL), use the nat64 logging command in global configuration mode. To disable NAT64 logging, use the no form of this command.
nat64 logging translations flow-export v9 udp destination hostname port
no nat64 logging translations
Syntax Description
translations
Enables NAT64 translation logging.
flow-export
Enables NAT64 logging through flow export.
v9
Enables Version 9 NetFlow export format logging.
udp
Enables logging of UDP packets.
destination
Specifies the NAT64 external logging destination.
hostname
Hostname or the IPv4 address of the external collector for logging records.
port
Port number of the IPv4 host of the external collector for logging records. Valid values are from 1 to 65535.
Usage Guidelines
The nat64 logging command allows you to specify remote logging for NAT64 objects.
The nat64 logging command is based on the NetFlow Version 9 export format.
In Cisco IOS XE Release 3.4S and later releases, NAT supports HSL. When HSL is configured, NAT provides a log of the packets that are flowing through the routing devices (similar to the Version 9 NetFlow-like records) to an external collector.
nat64 map-t
To configure the Network Address Translation 64 (NAT64) mapping of addresses and ports translation (MAP-T) settings, use the nat64 map-t command in global configuration mode. To remove the NAT64 MAP-T settings, use the no form of this command.
Usage Guidelines
MAP-T or Mapping of address and port (MAP) double stateless translation-based solution (MAP-T) provides IPv4 hosts connectivity to and across an IPv6 domain. MAP-T builds on existing stateless IPv4/IPv6 address translation techniques that are specified in RFC 6052, RFC 6144, and RFC 6145.
After you configure the nat64 map-t command, the command mode changes to NAT64 MAP-T configuration mode.
nat64 prefix stateful
To configure a prefix and a prefix length for stateful Network Address Translation 64 (NAT64), use the nat64 prefix stateful command in global configuration or interface configuration mode. To disable the configuration, use the no form of this command.
Syntax Description
ipv6-prefix
IPv6 network number to include in router advertisements. This argument must be in the form documented in RFC 2373 where the address is specified in hexadecimal using 16-bit values between colons.
/prefix-length
Length of the IPv6 prefix. A decimal value that indicates how many of the high-order contiguous bits of the address comprise the prefix (the network portion of the address). A slash mark must precede the decimal value.
Usage Guidelines
Use the nat64 prefix stateful command in global configuration mode to assign a global NAT64 stateful prefix, or use it in interface configuration mode to assign a unique NAT64 stateful prefix for an interface. A maximum of one global stateful prefix and one stateful prefix per interface is supported. If a global stateful prefix or an interface stateful prefix is not configured, the Well Known Prefix (WKP) of 64:ff9b::/96 is used to translate the IPv4 address of the IPv4 host.
Examples
The following example shows how to configure a global NAT64 stateful prefix:
Router(config)# nat64 prefix stateful 2001:DB8:0:1::/96The following example shows how to configure a NAT64 stateful prefix for a Gigabit Ethernet interface:
Router(config)# interface gigabitethernet0/0/0 Router(config-if)# nat64 prefix stateful 2001:DB8:0:1::/96nat64 prefix stateless
To assign a global or interface-specific Network Address Translation 64 (NAT64) stateless prefix, use the nat64 prefix stateless command in global configuration or interface configuration mode. To disable the configuration, use the no form of this command.
Syntax Description
ipv6-prefix
IPv6 network number to include in router advertisements. This argument must be in the form documented in RFC 2373 where the address is specified in hexadecimal using 16-bit values between colons.
/ prefix-length
Length of the IPv6 prefix. A decimal value that indicates how many of the high-order contiguous bits of the address comprise the prefix (the network portion of the address). A slash mark must precede the decimal value.
Usage Guidelines
The nat64 prefix stateless command uses a prefix and prefix length for IPv4-translatable IPv6 addresses. Use the nat64 prefix stateless command in global configuration mode to assign a global NAT64 stateless prefix or in interface configuration mode to assign an unique NAT64 stateless prefix for each interface. In interface configuration mode, a stateless prefix should be configured on an IPv6-facing interface.
All packets coming to an IPv6 interface are matched against the configured prefix, and the matched packets are translated to IPv4. Similarly, the packets that the IPv6 interface sends use the stateless prefix to construct the source and destination IPv6 address.
Note
A maximum of one global stateless prefix and one stateless prefix per interface is supported.
If NAT64 is enabled on an interface that does not have a stateless prefix configured, then the global stateless prefix is used. However, if a global prefix and an interface prefix are configured, then the interface prefix is used for stateless NAT64 translation. The use of a stateless prefix on an interface has priority over the configured global stateless prefix.
Examples
The following example shows how to configure a global NAT64 stateless prefix:
Device# configure terminal Device(config)# nat64 prefix stateless 2001::DB8::1/96 Device(config)# endThe following example shows how to assign a NAT64 stateless prefix for a Gigabit Ethernet interface:
Device# configure terminal Device(config)# interface gigabitethernet0/0/0 Device(config-if)# nat64 prefix stateless 2001:0DB8:0:1::/96 Device(config-if# endnat64 route
To specify the Network Address Translation 64 (NAT64) prefix to which an IPv4 prefix should be translated, use the nat64 route command in global configuration mode. To disable the configuration, use the no form of this command.
Syntax Description
ipv4-prefix / mask
Length of the IPv4 prefix and the mask.
interface-type
Interface type. For more information, use the question mark (?) online help function.
interface-number
Interface or subinterface number. For more information about the numbering syntax for your networking device, use the question mark (?) online help function.
Usage Guidelines
A prefix that is configured on an interface is used as the stateless prefix on that interface. If no interface-specific prefix is configured, the configured global prefix is used for NAT64 translation.
nat64 service ftp
To enable the Network Address Translation 64 (NAT64) FTP service, use the nat64 service ftp command in global configuration mode. To disable the NAT64 FTP service, use the no form of this command.
Usage Guidelines
Service FTP is an application-level gateway (ALG) that helps NAT64 operate on Layer 7 data.
nat64 settings
To configure Network Address Translation 64 (NAT64) settings, use the nat64 settings command in global configuration mode. To disable NAT64 settings, use the no form of this command.
nat64 settings { fragmentation header disable | v4 tos ignore }
no nat64 settings { fragmentation header disable | v4 tos ignore }
Usage Guidelines
By default, NAT64 adds a fragmentation header for all IPv4-to-IPv6 packets that do not have the Do Not Fragment (DF) bits set. Configure the nat64 settings fragmentation header disable command to disable the adding of a fragmentation header for packets that are not fragmented.
By default, NAT64 copies ToS bits from an IPv4 header to an IPv6 header. Configure the nat64 settings v4 tos ignore command to disable the copying of ToS bits from an IPv4 header to IPv6 header.
nat64 settings eif
To enable the Network Address Translation 64 (NAT64) end-point independent filtering (EIF), use the nat64 settings eif command in global configuration mode. To disable the EIF settings, use the no form of this command.
nat64 settings flow-entries disable
To disable flow cache entries in Network Address Translation 64 (NAT64) configurations, use the nat64 settings flow-entries disable command in global configuration mode. To enable flow cache entries in NAT64 configurations, use the no form of this command.
Usage Guidelines
Note
Disabling flow cache entries will result in lesser performance as this functionality performs multiple database searches to find the most specific translation to use.By default, Network Address Translation (NAT) creates a session (which is a 5-tuple entry) for every translation. A session is also called a flow cache entry.
NAT64 (stateful and stateless) translations support the disabling of flow cache entries. You can disable flow cache entries in dynamic and static NAT64 configurations. Instead of creating sessions, dynamic and static NAT64 translations can translate a packet off the binding (or bindings if both inside and outside bindings are available). A binding or a half entry is an association between a local IP address and a global IP address.
Disabling flow cache entries for dynamic and static translations saves memory usage and provides more scalability for your NAT64 translations.
NotePort Address Translation (PAT) or interface overload does not support disabling of flow cache entries.
Examples
The following example shows how to enable flow cache entries in a static NAT64 configuration:
Device# configure terminal Device(config)# ipv6 unicast-routing Device(config)# nat64 prefix stateful 2001:DB8:1::1/96 Device(config)# nat64 v6v4 static 2001:DB8:1::FFFE 209.165.201.1 Device(config)# no nat64 settings flow-entries disableRelated Commands
Command
Description
ipv6 unicast-routing
Enables the forwarding of IPv6 unicast datagrams.
nat64 prefix stateful
Configures a prefix and a prefix length for stateful NAT64.
nat64 prefix stateless
Assigns a global or interface-specific NAT64 stateless prefix.
nat64 v6v4
Translates an IPv6 source address to an IPv4 source address and an IPv4 destination address to an IPv6 destination address for NAT64.
nat64 settings mtu minimum
To set the minimum size for the Network Address Translation 64 (NAT64) maximum transmission units (MTU), use the nat64 settings mtu minimum command in interface configuration mode. To return to the default MTU size of 1280 bytes, use the no form of this command.
Usage Guidelines
Each interface has a default maximum packet size or MTU size. The MTU size of an interface defaults to the largest size possible for that interface type. To adjust the MTU size of an interface, configure the mtu command. Packets are fragmented based on the configured MTU size.
If the Do Not Fragment (DF) bits are not set, during the NAT64 translation and fragmentation of IPv4 packets to IPv6, NAT64 assumes that the IPv6 link minimum MTU size is 1280 bytes. However, the link MTU size could be greater than the minimum IPv6 link MTU size. To better utilize the network, network administrators can use the nat64 settings mtu minimum command to set a higher minimum MTU size. For example, if interfaces in a network are all Ethernet interfaces and the MTU size is 1500 bytes, fragmenting packets at 1280 bytes is not an effective utilization of the bandwidth. In this case, the network administrator can change the MTU size to 1500 bytes. When the nat64 settings mtu minimum command is configured, NAT64 ignores the implicit minimum MTU of 1280 bytes and fragments IPv6 packets based on the configured MTU size.
NoteThe nat64 settings mtu minimum command works only on IPv6-facing interfaces.
nat64 switchover replicate http
To replicate the Network Address Translation 64 (NAT64) HTTP switchover settings, use the nat64 switchover replicate http command in global configuration mode. To disable the HTTP switchover replication settings, use the no form of this command.
nat64 switchover replicate http { enable | disable } port port-number
no nat64 switchover replicate http
Usage Guidelines
In stateful NAT64 intra-chassis redundancy, HTTP sessions are not backed up on the standby Forward Processor (FP). A typical HTTP application has short-lived, transient flows. Because of the transient nature of the HTTP flows, these flows are not replicated. With stateful NAT64 intra-chassis redundancy you have the ability to replicate HTTP sessions so that HTTP flows can be made to live longer. To replicate HTTP sessions on the standby FP during a switchover, you must configure the nat64 switchover replicate http enable command.
You can enable and disable the replication of HTTP sessions on ports. For example, you can configure the nat64 switchover replicate http port 80 command and replicate the switchover of HTTP sessions on port 80. Configure the nat64 switchover replicate http disable port 8080 command to disable the replication of HTTP sessions on port 8080. You can disable the replication of sessions on only one port at any given time; however, you can enable the replication of sessions on all ports.
nat64 translation
To enable Network Address Translation 64 (NAT64) translation, use the nat64 translation command in global configuration mode. To disable NAT64 translation, use the no form of this command.
nat64 translation { max-entries limit | timeout { icmp | tcp | tcp-transient | udp } seconds }
nat64 translation { max-entries | timeout { icmp | tcp | tcp-transient | udp } }
Syntax Description
max-entries
Configures the maximum number of stateful NAT64 translations allowed on a router.
limit
NAT64 translation entry limit. Valid values are from 1 to 2147483647.
timeout
Specifies the NAT64 translation entry timeout.
icmp
Specifies the timeout for NAT64 Internet Control Message Protocol (ICMP) traffic flow.
tcp
Specifies the timeout for NAT64 established TCP traffic flow.
tcp-transient
Specifies the timeout for NAT64 transient TCP traffic flow.
udp
Specifies the timeout for NAT64 UDP traffic flow.
seconds
Traffic timeout, in seconds. Valid values are from 1 to 536870.
Usage Guidelines
The nat64 translation timeout command overrides the default aging timeout for NAT64 translations.
A transient TCP session has three possible conditions: a synchronize (SYN) handshake is started, but it is not complete; a reset (RST) packet is received; or a finished (FIN) packet is received in both directions.
nat64 v4
To enable Network Address Translation 64 (NAT64) IPv4 configuration, use the nat64 v4 command in global configuration mode. To disable the NAT64 IPv4 configuration, use the no form of this command.
nat64 v4 pool pool-name start-address-range end-address-range
no nat64 v4 pool pool-name [ forced | start-address-range end-address-range [ forced ] ]
Syntax Description
pool
Configures an IPv4 address pool.
pool-name
Name of the IPv4 address pool.
start-address-range
Starting address of the address pool range.
end-address-range
Ending address of the address pool range.
forced
(Optional) Removes the configuration even when the NAT64 translation exists for the configuration.
Usage Guidelines
In Cisco IOS XE Release 3.4S, the Stateful NAT64 feature supports only single range pools.
nat64 v4v6
To translate an IPv4 source address to an IPv6 source address and an IPv6 destination address to an IPv4 destination address for Network Address Translation 64 (NAT64), use the nat64 v4v6 command in global configuration mode. To disable the translation, use the no form of this command.
nat64 v4v6 static { ipv4-address ipv6-address | tcp ipv4-address port ipv6-address port | udp ipv4-address port ipv6-address port } [ redundancy group-id mapping-id id ]
no nat64 v4v6 static { ipv4-address ipv6-address | [ forced ] | tcp ipv4-address port ipv6-address port | udp ipv4-address port ipv6-address port } [ forced ] [ redundancy group-id mapping-id id ]
Syntax Description
static
Associates an IPv6 address to an IPv4 host statically.
ipv4-address
Address of the IPv4 host.
ipv6-address
IPv6 address to which the IPv4 host is mapped to in the IPv6 network.
tcp
Applies static mapping to TCP protocol packets.
port
Port number of the IPv6 or IPv4 address. Valid values are from 1 to 65535.
udp
Applies static mapping to UDP protocol packets.
redundancy group-id
(Optional) Configures a redundancy group (RG) with the specified ID. Valid values are 1 and 2.
mapping-id id
(Optional) Configures a unique ID for mapping devices. The same ID should be configured on both active and standby devices. Valid values are from 1 to 20480.
forced
(Optional) Removes the configuration even when the NAT64 translation exists for the configuration.
Examples
The following example shows how to enable static mapping of an IPv4 address to an IPv6 address:
Device(config)# nat64 v4v6 static 192.168.0.1 2001:DB8:0::1The following example shows how to configure a redundancy group to a static IPv4-to-IPv6 address configuration:
Device(config)# nat64 v4v6 static 192.168.0.1 2001:DB8:0::1 redundancy 1 mapping-id 101nat64 v6v4
To translate an IPv6 source address to an IPv4 source address and an IPv4 destination address to an IPv6 destination address for Network Address Translation 64 (NAT64), use the nat64 v6v4 command in global configuration mode. To disable the translation, use the no form of this command.
nat64 v6v4 { list access-list-name pool pool-name [ overload ] | static { ipv6-address ipv4-address | tcp ipv6-address port ipv4-address port | udp ipv6-address port ipv4-address port } } [ redundancy group-id mapping-id id ]
no nat64 v6v4 { list access-list-name pool pool-name [ overload ] | static { ipv6-address ipv4-address | tcp ipv6-address port ipv4-address port | udp ipv6-address port ipv4-address port } } [ forced ] [ redundancy group-id mapping-id id ]
Syntax Description
list
Associates an IPv4 pool with the filtering mechanism that decides when to apply an IPv6 address mapping.
access-list-name
Name of the IPv6 access list.
pool
Specifies the NAT64 pool for dynamic mapping of addresses.
pool-name
Name of the NAT64 pool.
overload
(Optional) Enables NAT64 overload address translation.
static
Enables NAT64 static mapping of addresses.
ipv6-address
IPv6 address of the IPv6 host to which static mapping is applied.
ipv4-address
IPv4 address that represents the IPv6 host for static mapping in the IPv4 network.
tcp
Applies static mapping to TCP protocol packets.
port
Port number of the IPv6 or IPv4 address. Valid values are from 1 to 65535.
udp
Applies static mapping to UDP protocol packets.
redundancy group-id
(Optional) Configures a redundancy group (RG). Valid values are 1 and 2.
mapping-id id
(Optional) Configures a unique ID for mapping devices. The same ID should be configured on both active and standby devices. Valid values are from 1 to 20480.
forced
(Optional) Removes the configuration even when the NAT64 translation exists for the configuration.
Examples
The following example shows how to enable dynamic mapping of an IPv6 address to an IPv4 address pool:
Device(config)# nat64 v6v4 list list1 pool pool1The following example shows how to configure an RG for a dynamic IPv6-to-IPv4 address pool:
Device(config)# nat64 v6v4 list list1 pool pool1 redundancy 1 mapping-id 203netbios-name-server
To configure NetBIOS Windows Internet Naming Service (WINS) name servers that are available to Microsoft Dynamic Host Configuration Protocol (DHCP) clients, use the netbios-name-server command in DHCP pool configuration. To remove the NetBIOS name server list, use the no form of this command.
Command History
Release
Modification
12.0(1)T
This command was introduced.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2SX
This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.
Usage Guidelines
One IP address is required, although you can specify up to eight addresses in one command line. Servers are listed in order of preference (address1 is the most preferred server, address2 is the next most preferred server, and so on).
Examples
The following example specifies the IP address of a NetBIOS name server available to the client:
netbios-name-server 10.12.1.90Related Commands
Command
Description
dns-server
Specifies the DNS IP servers available to a DHCP client.
domain-name (DHCP)
Specifies the domain name for a DHCP client.
ip dhcp pool
Configures a DHCP address pool on a Cisco IOS DHCP Server and enters DHCP pool configuration mode.
netbios-node-type
Configures the NetBIOS node type for Microsoft DHCP clients.
netbios-node-type
To configure the NetBIOS node type for Microsoft Dynamic Host Configuration Protocol (DHCP) clients, use the netbios-node-type command in DHCP pool configuration mode. To remove the NetBIOS node type, use the no form of this command.
Command History
Release
Modification
12.0(1)T
This command was introduced.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2SX
This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.
network (DHCP)
To configure the network number and mask for a Dynamic Host Configuration Protocol (DHCP) address pool primary or secondary subnet on a Cisco IOS DHCP server, use the network command in DHCP pool configuration mode. To remove the subnet number and mask, use the no form of this command.
Syntax Description
Command History
Release
Modification
12.0(1)T
This command was introduced.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(33)SRB
This command was modified. The secondary keyword was added.
12.2SX
This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.
Cisco IOS XE Release 3.1S
This command was integrated into Cisco IOS XE Release 3.1S and implemented on the Cisco ASR 1000 Series Aggregation Services Routers.
15.0(1)S
This command was integrated into Cisco IOS Release 15.0(1)S.
Usage Guidelines
This command is valid for DHCP subnetwork address pools only.
The DHCP server assumes that all host addresses are available. The system administrator can exclude subsets of the address space by using the ip dhcp excluded-address global configuration command. However, the ip dhcp excluded-address command cannot be used to exclude addresses from virtual routing and forwarding (VRF)-associated pools.
You cannot configure manual bindings within the same pool that is configured with the network command.
If a default router list is configured for the pool or subnet from which the address was allocated, the DHCP server selects an IP address from that default router list and provides it to the client. The DHCP client uses that router as the first hop for forwarding messages.
Removing a secondary subnet also removes the default router list for that subnet. Removing the primary subnet removes only the primary subnet definition but not the network-wide default router list.
To display the DHCP address pool information configured by the network command, use the show ip dhcp pool command.
Examples
The following example shows how to configure 172.16.0.0/12 as the subnetwork number and mask of the DHCP pool named pool1. The IP addresses in pool1 range from 172.16.0.0 to 172.31.255.255.
Router(config)# ip dhcp pool pool1 Router(dhcp-config)# network 172.16.0.0 255.240.0.0The following example shows how to configure 192.0.2.0/24 as the subnetwork number and mask of the DHCP pool named pool2 and then add the DHCP pool secondary subnet specified by the subnet number and mask 192.0.4.0/30. The IP addresses in pool2 consist of two unconnected subnets: the addresses from 192.0.2.1 to 192.0.2.254 and the addresses from 192.0.4.1 to 192.0.4.2.
Router(config)# ip dhcp pool pool2 Router(dhcp-config)# network 192.0.2.0 255.255.255.0 Router(dhcp-config)# network 192.0.4.0 255.255.255.252 secondaryRelated Commands
Command
Description
default-router
Specifies the IP address of the default router for a DHCP client.
host
Specifies the IP address and network mask for a manual binding to a DHCP client.
ip dhcp excluded-address
Specifies IP addresses that a Cisco IOS DHCP server should not assign to DHCP clients.
ip dhcp pool
Configures a DHCP address pool on a Cisco IOS DHCP server and enters DHCP pool configuration mode.
override default-router
Configures a subnet-specific default router list for the DHCP pool secondary subnet.
show ip dhcp pool
Displays information about the DHCP address pools.
next-server
To configure the next server in the boot process of a Dynamic Host Configuration Protocol (DHCP) client, use the next-server command in DHCP pool configuration. To remove the boot server list, use the no form of this command.
Syntax Description
address
Specifies the IP address of the next server in the boot process, which is typically a Trivial File Transfer Protocol (TFTP) server. One IP address is required, but up to eight addresses can be specified in one command line.
address2 ...address8
(Optional) Specifies up to seven additional addresses in the command line.
Command Default
If the next-server command is not used to configure a boot server list, the DHCP Server uses inbound interface helper addresses as boot servers.
Command History
Release
Modification
12.0(1)T
This command was introduced.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2SX
This command is supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.
Usage Guidelines
You can specify up to eight servers in the list. Servers are listed in order of preference (address1 is the most preferred server, address2 is the next most preferred server, and so on).
Examples
The following example specifies 10.12.1.99 as the IP address of the next server in the boot process:
next-server 10.12.1.99Related Commands
Command
Description
accounting (DHCP)
Specifies the name of the default boot image for a DHCP client.
ip dhcp pool
Configures a DHCP address pool on a Cisco IOS DHCP server and enters DHCP pool configuration mode.
ip helper-address
Forwards UDP broadcasts, including BOOTP, received on an interface.
option
Configures Cisco IOS DHCP server options.
nhrp group
To configure a Next Hop Resolution Protocol (NHRP) group on a spoke, use the nhrp group command in interface configuration mode. To remove an NHRP group, use the no form of this command.
Usage Guidelines
After you create an NHRP group on a spoke, you use the nhrp map group command to map the group to a QoS policy map.
Note
This command will replace the ip nhrp group command in a future release.Examples
The following example shows how to create two NHRP groups named small and large.
Device> enable Device# configure terminal Device(config)# interface Tunnel 0 Device(config-if)# nhrp group small Device(config-if)# nhrp group largeRelated Commands
Command
Description
ip nhrp map Statically configures the IP-to-NBMA address mapping of IP destinations connected to an NBMA network.
nhrp map group Adds NHRP groups to QoS policy mappings on a hub.
show dmvpn Displays DMVPN-specific session information.
show nhrp Displays NHRP mapping information.
show nhrp group-map Displays the details of NHRP group mappings on a hub and the list of tunnels using each of the NHRP groups defined in the mappings.
show policy-map mgre Displays statistics about a specific QoS policy as it is applied to a tunnel endpoint.
nhrp map group
To associate a Next Hop Resolution Protocol (NHRP) group to a QoS policy map, use the nhrp map group command in interface configuration mode. To remove an association, use the no form of this command.
nhrp map group group-name service-policy output qos-policy-map-name
no nhrp map group group-name service-policy output qos-policy-map-name
Usage Guidelines
The command allows a QoS policy in the output direction only.
Note
This command will replace the ip nhrp map group command in a future release.Examples
The following example shows how to map two NHRP groups named small and large to two QoS policy maps named qos-small and qos-large respectively.
Device> enable Device# configure terminal Device(config)# interface Tunnel 0 Device(config-if)# nhrp map group small service-policy output qos-small Device(config-if)# nhrp map group large service-policy output qos-largeRelated Commands
Command
Description
ip nhrp map Statically configures the IP-to-NBMA address mapping of IP destinations connected to an NBMA network.
nhrp group Configures an NHRP group on a spoke.
show dmvpn Displays DMVPN-specific session information.
show nhrp Displays NHRP mapping information.
show nhrp group-map Displays the details of NHRP group mappings on a hub and the list of tunnels using each of the NHRP groups defined in the mappings.
show policy-map mgre Displays statistics about a specific QoS policy as it is applied to a tunnel endpoint.
nis address
To specify the network information service (NIS) address of an IPv6 server to be sent to the client, use the nis address command in DHCP for IPv6 pool configuration mode. To remove the NIS address, use the no form of this command.
Usage Guidelines
The Dynamic Host Configuration Protocol (DHCP) for IPv6 for stateless configuration allows a DHCP for IPv6 client to export configuration parameters (that is, DHCP for IPv6 options) to a local DHCP for IPv6 server pool. The local DHCP for IPv6 server can then provide the imported configuration parameters to other DHCP for IPv6 clients.
The NIS server option provides a list of one or more IPv6 addresses of NIS servers available to send to the client. The client must view the list of NIS servers as an ordered list, and the server may list the NIS servers in the order of the server’s preference.
The NIS server option code is 27. For more information on DHCP options and suboptions, see the "DHCPv6 Options" appendix in the Network Registrar User's Guide , Release 6.2.
nis domain-name
To enable a server to convey a client’s network information service (NIS) domain name information to the client, use the nis domain-namecommand in DHCP for IPv6 pool configuration mode. To remove the domain name, use the no form of this command.
Usage Guidelines
The Dynamic Host Configuration Protocol (DHCP) for IPv6 for stateless configuration allows a DHCP for IPv6 client to export configuration parameters (that is, DHCP for IPv6 options) to a local DHCP for IPv6 server pool. The local DHCP for IPv6 server can then provide the imported configuration parameters to other DHCP for IPv6 clients.
The NIS domain name option provides a NIS domain name for the client. Use the nis domain-name command to specify the client’s NIS domain name that the server sends to the client.
The NIS domain name option code is 29. For more information on DHCP options and suboptions, see the "DHCPv6 Options" appendix in the Network Registrar User's Guide , Release 6.2.
nisp domain-name
To enable an IPv6 server to convey a client’s network information service plus (NIS+) domain name information to the client, use the nisp domain-namecommand in DHCP for IPv6 pool configuration mode. To remove the domain name, use the no form of this command.
Usage Guidelines
The Dynamic Host Configuration Protocol (DHCP) for IPv6 for stateless configuration allows a DHCP for IPv6 client to export configuration parameters (that is, DHCP for IPv6 options) to a local DHCP for IPv6 server pool. The local DHCP for IPv6 server can then provide the imported configuration parameters to other DHCP for IPv6 clients.
The NIS+ domain name option provides a NIS+ domain name for the client. Use the nisp domain-name command to enable a server to send the client its NIS+ domain name information.
The NIS+ domain name option code is 30. For more information on DHCP options and suboptions, see the "DHCPv6 Options" appendix in the Network Registrar User's Guide , Release 6.2.
nisp address
To specify the network information service plus (NIS+) address of an IPv6 server to be sent to the client, use the nisp address command in DHCP for IPv6 pool configuration mode. To remove the NIS+ address, use the no form of the command.
Usage Guidelines
The Dynamic Host Configuration Protocol (DHCP) for IPv6 for stateless configuration allows a DHCP for IPv6 client to export configuration parameters (that is, DHCP for IPv6 options) to a local DHCP for IPv6 server pool. The local DHCP for IPv6 server can then provide the imported configuration parameters to other DHCP for IPv6 clients.
The NIS+ servers option provides a list of one or more IPv6 addresses of NIS+ servers available to send to the client. The client must view the list of NIS+ servers as an ordered list, and the server may list the NIS+ servers in the order of the server’s preference.
The NIS+ servers option code is 28. For more information on DHCP options and suboptions, see the "DHCPv6 Options" appendix in the Network Registrar User's Guide , Release 6.2.
odap client
To configure On–Demand Address Pooling (ODAP) client parameters, use the odap client command in DHCP pool configuration mode. To remove ODAP client parameters, use the no form of this command.
odap client { client-id id [ interface type number ] [ target-server ip-address ] | interface type number [ client-id id ] [ target-server ip-address ] | target-server ip-address [ client-id id ] [ interface type number ] }
no odap client { client-id id [ interface type number ] [ target-server ip-address ] | interface type number [ client-id id ] [ target-server ip-address ] | target-server ip-address [ client-id id ] [ interface type number ] }
Command Default
The outgoing interface for sending subnet allocation request is not configured.
The Cisco IOS DHCP ODAP client module prepares the client ID to be sent in the subnet allocation request by concatenating the router hostname with the subnet pool name.
The target ODAP server's IP address is not configured.
Usage Guidelines
Use the odap client command to configure ODAP client parameters. You must configure one of the parameters. The parameters can be specified in any order.
odap server
To configure On–Demand Address Pooling (ODAP) server parameters, use the odap server command in DHCP pool configuration mode. To remove the ODAP server parameter settings, use the no form of this command.
odap server { rebind-time percent-value [ renew-time percent-value ] | renew-time percent-value [ rebind-time percent-value ] }
no odap server { rebind-time percent-value [ renew-time percent-value ] | renew-time percent-value [ rebind-time percent-value ] }
Usage Guidelines
Use the odap server command to configure ODAP server parameters. You must specify either the rebind time or the renew time. You can specify the rebind time and renew time in any order. The rebind time cannot be less than the renew time.
option
To configure DHCP server options, use the option command in DHCP pool configuration mode. To remove the options, use the no form of this command.
option code [ instance number ] { ascii string | hex { string | none } | ip { address | hostname } }
no option code [ instance number ]
Syntax Description
code
Specifies the DHCP option code. The range is from 0 to 254.
instance number
(Optional) Specifies an instance number. The range is from 0 to 255. The default is 0.
ascii string
Specifies a network virtual terminal (NVT) ASCII character string. ASCII character strings that contain white spaces must be delimited by quotation marks. The ASCII value is truncated to 255 characters entered.
hex
Specifies dotted hexadecimal data.
string
Hexadecimal value truncated to 180 characters entered. Each byte in hexadecimal character strings is two hexadecimal digits. Each byte can be separated by a period, colon, or white space.
none
Specifies the zero-length hexadecimal string.
ip address
Specifies an IP address. More than one IP address can be specified.
ip hostname
Specifies the hostname. More than one hostname can be specified.
Command History
Release
Modification
12.0(1)T
This command was introduced.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2SX
This command was supported in the Cisco IOS Release 12.2SX train. Support in a specific 12.2SX release of this train depends on your feature set, platform, and platform hardware.
12.4(24)T
This command was modified. The none keyword was added.
15.1(3)S
This command was modified. A maximum limit of 180 characters was set for the dotted hexadecimal data and 255 characters for the ASCII data.
Usage Guidelines
DHCP provides a framework for passing configuration information to hosts on a TCP/IP network. The configuration parameters and other control information are carried in tagged data items that are stored in the options field of the DHCP message. The data items themselves are also called options. The current set of DHCP options is documented in RFC 2131, Dynamic Host Configuration Protocol.
Examples
The following example shows how to configure DHCP option 19, which specifies whether the client should configure its IP layer for packet forwarding. A value of 0 means disable IP forwarding; a value of 1 means enable IP forwarding. IP forwarding is enabled in the following example.
Router(config)# ip dhcp pool red Router(dhcp-config)# option 19 hex 01The following example shows how to configure DHCP option 72, which specifies the World Wide Web servers for DHCP clients. World Wide Web servers 172.16.3.252 and 172.16.3.253 are configured in the following example.
Router(config)# ip dhcp pool red Router(dhcp-config)# option 72 ip 172.16.3.252 172.16.3.253option hex
To enable the Cisco IOS relay agent to make forwarding decisions based on DHCP options inserted in the client-generated DHCP message, use the option hexcommand in DHCP class configuration mode. To disable this functionality, use the no form of this command.
option code hex hex-pattern [*] [ bit bit-mask-pattern ]
no option code hex hex-pattern [*] [ mask bit-mask-pattern ]
Syntax Description
code
Specifies the DHCP option code. Valid values are 60, 77, 124, and 125. All other values will be rejected with the appropriate error message.
hex-pattern
String of hexadecimal values. This string creates a pattern that is matched against the named DHCP class. The hex-pattern argument represents the data portion of the DHCP option format. See “Usage Guidelines” below for more information.
*
(Optional) Wildcard character.
mask bit-mask-pattern
(Optional) String of hexadecimal values. Specifies the bit mask to be applied to the hex-pattern argument.
Usage Guidelines
The option hex command enhances DHCP class support to allow the relay agent to relay client-generated messages to different DHCP servers based on the content of the following four options:
- Option 60: vendor class identifier
- Option 77: user class
- Option 124: vendor-identifying vendor class
- Option 125: vendor-identifying vendor-specific information
Each option identifies the type of client sending the DHCP message.
The table below describes the CLI variations possible for the hex hex-pattern keyword and argument combination.
Table 1 option hex CLI Variations Hex string format variations
CLI example
Description
Full option value as raw hex
This option has 3 bytes of data with 0x010203 hex as the content.
Bit-masked hex string
This option is the same as above except that only the first 2 bytes of data should be 0x0102.
Wild-carded hex string
This option should have at least 3 bytes, with the first 3 bytes matching the specified hex pattern.
You must know the hexadecimal value of each byte location in the options to be able to configure the option hex command. The format may vary from product to product. Contact the relay agent vendor for this information.
Examples
In the following example, client-generated DHCP messages containing option 60 and belonging to class VOIP will be forwarded to the DHCP server located at 10.30.5.1:
! ip dhcp class VOIP option 60 hex 010203 ! ! The following is the relay pool ip dhcp pool red relay source 10.2.2.0 255.255.255.0 class VOIP relay target 10.30.5.1option ext
To configure DHCP extended server options, use the option ext command in DHCP pool configuration mode. To remove the options, use the no form of this command.
Syntax Description
code
Specifies the DHCP option code. The range is from 0 to 254.
ascii string
Specifies a network virtual terminal (NVT) ASCII character string. ASCII character strings that contain white space must be delimited by quotation marks.
hex string
Specifies dotted hexadecimal data. Each byte in hexadecimal character strings is two hexadecimal digits—each byte can be separated by a period, colon, or white space.
Usage Guidelines
Using the option ext command you can specify an ASCII string upto 255 characters or 255 bytes of hexadecimal data. To do this, you need to break the string into three sets and then execute the option ext command three times, specifying the three strings.
option ext 43 ascii <first 100 characters> option ext 43 ascii <next 100 characters> option ext 43 ascii <last 55 characters>If you want to enter 220 characters of ASCII data, you need to break the string into three, for example, two containing 100 characters each and the other containing the remaining 20 characters.
option ext 43 ascii <first 100 characters> option ext 43 ascii <next 100 characters> option ext 43 ascii <last 20 characters>At any time, you can append additional characters to the string if the maximum length (255 characters or bytes) is not reached.
Only single format can be used between consecutive extended commands; that is, you cannot enter the first 100 bytes in ASCII and the next 100 bytes in hexadecimal or vice versa. Also, only one type of option command can be used as consecutive commands. That is, you cannot enter the option command and then the option ext command.
Use the no option or no option ext command to remove the configured option and configure the new option using the option ext command.
Examples
The following example shows how to configure DHCP extended option 43 and an ASCII string with 25 characters. The ASCII string of 25 characters is configured using three option ext commands.
Router(config)# ip dhcp pool pool1 Router(dhcp-config)# option ext 43 ascii 1111111111 Router(dhcp-config)# option ext 43 ascii 1111111111 Router(dhcp-config)# option ext 43 ascii 11111Related Commands
Command
Description
ip dhcp pool
Configures a DHCP address pool on a Cisco IOS DHCP server and enters DHCP pool configuration mode.
option
Configures DHCP server options.
option hex
Enables the Cisco IOS relay agent to make forwarding decisions based on DHCP options inserted in the client-generated DHCP message.
origin
To configure an address pool as an on-demand address pool (ODAP) or static mapping pool, use the origin command in DHCP pool configuration mode. To disable the ODAP, use the no form of this command.
origin { dhcp [ number number | subnet size initial size [ autogrow size ] ] | aaa [ subnet size initial size [ autogrow size ] ] | file url [ refresh [ interval minutes ] ] | ipcp }
no origin { dhcp [ number number | subnet size initial size [ autogrow size ] ] | aaa [ subnet size initial size [ autogrow size ] ] | file url [ refresh [ interval minutes ] ] | ipcp }
Syntax Description
dhcp
Specifies Dynamic Host Configuration Protocol (DHCP) as the subnet allocation protocol.
number number
(Optional) Specifies the number of subnets to request. The range is from 1 to 5.
subnet size initial size
(Optional) Specifies the initial size of the first requested subnet. You can enter the value for the size argument as either the subnet mask (nnnn.nnnn.nnnn.nnnn) or prefix size (/nn). The valid values are /0 and /4 to /30.
autogrow size
(Optional) Specifies that the pool can grow incrementally. The value for the size argument is the size of the requested subnets when the pool requests additional subnets (upon detection of high utilization). You can enter the value for the size as either the subnet mask (nnnn.nnnn.nnnn.nnnn) or prefix size (/nn). The valid values are /0 and /4 to /30.
aaa
Specifies authentication, authorization, and accounting (AAA) as the subnet allocation protocol.
file url
Specifies the external database file that contains the static bindings assigned by the DHCP server. The url argument specifies the location of the external database file.
refresh
Specifies to refresh or reread the DHCP static mapping file.
interval minutes
Specifies the refresh or reread interval, in minutes, for DHCP static mapping file. The range is from 1 to 500.
ipcp
Specifies the IP Control Protocol (IPCP) as the subnet allocation protocol.
Command History
Release
Modification
12.2(8)T
This command was introduced.
12.3(11)T
This command was modified. The file keyword was added.
12.2(28)SB
This command was integrated into Cisco IOS Release 12.2(28)SB.
15.2(1)T
This command was modified. The number, refresh, and interval keywords and the number and minutes arguments were added.
Usage Guidelines
If you do not configure the pool as an autogrow pool, the pool will not request additional subnets if one subnet is already in the pool.
Use the dhcp keyword to obtain subnets from DHCP, the aaa keyword to obtain subnets from the AAA server, and the ipcp keyword to obtain subnets from IPCP negotiation. If you expect that the utilization of the pool may grow over time, use the autogrow size option.
If a pool has been configured with the autogrow size option, ensure that the source server can provide more than one subnet to the same pool. Even though the Cisco IOS software specifies the requested subnet size, it can accept any offered subnet size from the source server.
Examples
The following example shows how to configure an address pool named pool1 to use DHCP as the subnet allocation protocol with an initial subnet size of 24 and an autogrow subnet size of 24:
ip dhcp pool pool1 vrf pool1 origin dhcp subnet size initial /24 autogrow /24 utilization mark high 80 utilization mark low 20The following example shows how to configure the location of the external text file:
ip dhcp pool abcpool origin file tftp://10.1.0.1/staticbindingfileoverride default-router
To define a default router list for the DHCP pool secondary subnet, use the override default-router command in DHCP pool secondary subnet configuration mode. To remove the default router list for this secondary subnet, use the no form of this command.
Syntax Description
address
IP address of the default router for the DHCP pool secondary subnet, preferably on the same subnet as the DHCP pool secondary client subnet.
address2 ... address8
(Optional) IP addresses of up to seven additional default routers, delimited by a single space.
Note The ellipses in the syntax description are used to indicate a range of values. Do not use ellipses when entering IP addresses.
Usage Guidelines
When an IP address is assigned to the DHCP client from a secondary subnet for which no subnet-specific default router list is defined, the default router list (configured by using the default-router command in DHCP pool configuration mode) will be used.
The IP address of every router in the list should be on the same subnet as the client subnet. You can specify up to eight routers in the list. Routers are listed in order of preference (address is the most preferred router, address2 is the next most preferred router, and so on).
To display the default router lists, use the show running-config command. If default router lists are configured for a DHCP pool, the commands used to configure those lists are displayed following the ip dhcp pool command that configures the DHCP pool.
Examples
The following example configures 10.1.1.1/29 as the subnetwork number and mask of the DHCP pool named pool1, adds the DHCP pool secondary subnet specified by the subnet number and mask 10.1.1.17/29, then configures a subnet-specific default router list for that subnet:
Router(config)# dhcp pool pool1 Router(config-dhcp)# network 10.1.1.1 255.255.255.248 Router(config-dhcp)# network 10.1.1.17 255.255.255.248 secondary Router(config-dhcp-secondary-subnet)# override default-router 10.1.1.100 10.1.1.200override utilization high
To configure the high utilization mark of the current secondary subnet size, use the override utilization high command in DHCP pool secondary subnet configuration mode. To remove the high utilization mark, use the no form of this command.
Usage Guidelines
If you use the utilization mark {high | low} log command, a system message can be generated for a DHCP secondary subnet when the subnet utilization exceeds the configured high utilization threshold. A system message can also be generated when the subnet’s utilization is detected to be below the configured low utilization threshold.
The override utilization high command overrides the value specified by the utilization mark high global configuration command.
Examples
The following example shows how to set the high utilization mark of the secondary subnet to 40 percent of the current subnet size:
Router(config)# ip dhcp pool pool2 Router(dhcp-config)# utilization mark high 80 log Router(dhcp-config)# utilization mark low 70 log Router(dhcp-config)# network 192.0.2.0 255.255.255.0 Router(dhcp-config)# network 192.0.4.0 255.255.255.252 secondary Router(config-dhcp-subnet-secondary)# override utilization high 40 Router(config-dhcp-subnet-secondary)# override utilization low 30override utilization low
To configure the low utilization mark of the current secondary subnet size, use the override utilization low command in DHCP pool secondary subnet configuration mode. To remove the low utilization mark, use the no form of this command.
Usage Guidelines
If you use the utilization mark{high| low} log command, a system message can be generated for a DHCP secondary subnet when the subnet utilization falls below the configured low utilization threshold. A system message can also be generated when the subnet’s utilization exceeds the configured high utilization threshold.
The override utilization low command overrides the value specified by the utilization mark low global configuration command.
Examples
The following example shows how to set the low utilization mark of the secondary subnet to 30 percent of the current subnet size:
Router(config)# ip dhcp pool pool2 Router(dhcp-config)# utilization mark high 80 log Router(dhcp-config)# utilization mark low 70 log Router(dhcp-config)# network 192.0.2.0 255.255.255.0 Router(dhcp-config)# network 192.0.4.0 255.255.255.252 secondary Router(config-dhcp-subnet-secondary)# override utilization high 40 Router(config-dhcp-subnet-secondary)# override utilization low 30port-parameters
To configure port parameters for a Network Address Translation 64 (NAT64) mapping of addresses and ports (MAP-T) basic mapping rule, use the port-parameters command in NAT64 MAP-T BMR configuration mode. To remove the port parameters, use the no form of this command.
Usage Guidelines
MAP-T or Mapping of address and port (MAP) double stateless translation-based solution (MAP-T) provides IPv4 hosts connectivity to and across an IPv6 domain. MAP-T builds on existing stateless IPv4/IPv6 address translation techniques that are specified in RFC 6052, RFC 6144, and RFC 6145.
preempt
To enable preemption on the redundancy group, use the preemptcommand in redundancy application group configuration mode. To disable the group’s preemption, use the no form of this command.
Usage Guidelines
When the preemption is enabled, it means that a standby redundancy group should preempt an active redundancy group if its priority is higher than the active redundancy group.
NoteIf you allocate a large amount of memory to the log buffer (e.g. 1 GB), then the CPU and memory utilization of the router increases. This issue is compounded if small intervals are set for the hellotime and the holdtime. If you want to allocate a large amount of memory to the log buffer, we recommend that you accept the default values for the hellotime and holdtime. For the same reason, we also recommend that you do not use the preempt command.
preference (DHCPv6 Guard)
To enable verification that the advertised preference (in preference option) is greater than the minimum specified limit and less than the maximum specified limit, use the preference command in Dynamic Host Configuration Protocol version 6 (DHCPv6) guard configuration mode. To remove the preference, use the no form of this command.
Usage Guidelines
This command enables verification that the advertised preference is not greater than the maximum specified limit or less than the minimum specified limit.
Examples
The following example defines an DHCPv6 guard policy name as policy1, places the router in DHCPv6 guard configuration mode, and enables verification that the advertised preference is not greater than 254 or less than 2:
Router(config)# ipv6 dhcp guard policy policy1 Router(config-dhcp-guard)# preference min 2 Router(config-dhcp-guard)# preference max 254prefix-delegation
To specify a manually configured numeric prefix to be delegated to a specified client (and optionally a specified identity association for prefix delegation [IAPD] for that client), use the prefix-delegation command in DHCP for IPv6 pool configuration mode. To remove the prefix, use the no form of this command.
prefix-delegation ipv6-prefix/prefix-length client-DUID [ iaid iaid ] [lifetime]
no prefix-delegation ipv6-prefix/prefix-length client-DUID [ iaid iaid ]
Syntax Description
ipv6-prefix
(Optional) Specified IPv6 prefix.
This argument must be in the form documented in RFC 2373 where the address is specified in hexadecimal using 16-bit values between colons.
/ prefix-length
The length of the IPv6 prefix. A decimal value that indicates how many of the high-order contiguous bits of the address comprise the prefix (the network portion of the address).
client-DUID
The DHCP unique identifier (DUID) of the client to which the prefix is delegated.
iaid iaid
(Optional) Identity association identifier (IAID), which uniquely identifies an IAPD on the client.
lifetime
(Optional) Sets a length of time over which the requesting router is allowed to use the prefix. The following values can be used:
- valid-lifetime --The length of time, in seconds, that the prefix remains valid for the requesting router to use.
- at --Specifies absolute points in time where the prefix is no longer valid and no longer preferred.
- infinite --Indicates an unlimited lifetime.
- preferred-lifetime --The length of time, in seconds, that the prefix remains preferred for the requesting router to use.
- valid-month valid-date valid-year valid-time --A fixed duration of time for hosts to remember router advertisements. The format to be used can be oct 24 2003 11:45 or 24 oct 2003 11:45
- preferred-month preferred-date preferred-year preferred-time-- A fixed duration of time for hosts to remember router advertisements. The format to be used can be oct 24 2003 11:45 or 24 oct 2003 11:45.
Usage Guidelines
Administrators can manually configure a list of prefixes and associated preferred and valid lifetimes for an IAPD of a specific client that is identified by its DUID. This static binding of client and prefixes can be specified based on users' subscription to an ISP using the prefix-delegationprefix-length command.
The client-DUID argument identifies the client to which the prefix is delegated. All the configured prefixes will be assigned to the specified IAPD of the client. The IAPD to which the prefix is assigned is identified by the iaid argument if the iaid keyword is configured. If the iaid keyword is not configured, the prefix will be assigned to the first IAPD from the client that does not have a static binding. This function is intended to make it convenient for administrators to manually configure prefixes for a client that only sends one IAPD in case it is not easy to know the iaid in advance.
When the delegating router receives a request from a client, it checks whether there is a static binding configured for the IAPD in the client’s message. If one is present, the prefixes in the binding are returned to the client. If no such binding is found, the server attempts to assign prefixes for the client from other sources.
Optionally valid and preferred lifetimes can be specified for the prefixes assigned from this pool. Users should coordinate the specified lifetimes with the lifetimes on prefixes from the upstream delegating router if the prefixes were acquired from that router.
The lifetimekeyword can be specified in one of two ways:
- A fixed duration that stays the same in consecutive advertisements.
- Absolute expiration time in the future so that advertised lifetime decrements in real time, which will result in a lifetime of 0 at the specified time in the future.
The specified length of time is between 60 and 4294967295 seconds or infinity if the infinite keyword is specified.
Examples
The following example configures an IAPD for a specified client:
prefix-delegation 2001:0DB8::/64 00030001000BBFAA2408Related Commands
Command
Description
ipv6 dhcp pool
Configures a DHCP for IPv6 pool and enters DHCP for IPv6 pool configuration mode.
ipv6 local pool
Configures a local IPv6 prefix pool.
prefix-delegation pool
Specifies a named IPv6 local prefix pool from which prefixes are delegated to DHCP for IPv6 clients.
show ipv6 dhcp pool
Displays DHCP for IPv6 configuration pool information.
prefix-delegation aaa
To specify that prefixes are to be acquired from authorization, authentication, and accounting (AAA) servers, use the prefix-delegation aaacommand in DHCP for IPv6 pool configuration mode. To disable this feature, use the no form of this command.
Cisco IOS Release 12.4(22)T and Earlier Releases and Cisco IOS Release 12.2(18)SXE, Cisco IOS XE Release 2.1, and Later Releases
prefix-delegation aaa [ method-list method-list [lifetime] { { valid-lifetime | infinite } { valid-lifetime | infinite } | at { date month year time | month date year time } { date month year time | month date year time } } ]
no prefix-delegation aaa method-list method-list
Cisco IOS Release 15.0(1)M and Later Releases
prefix-delegation aaa method-list { method-list | default } [ lifetime { valid-lifetime | infinite } { preferred-lifetime | infinite } | at { date month year time | month date year time } { date month year time | month date year time } ]
no prefix-delegation aaa method-list method-list
Syntax Description
method-list
(Optional) Indicates a method list to be defined.
method-list
Configuration type AAA authorization method list that defines how authorization will be performed.
default
Specifies the default method list, nvgened.
lifetime
(Optional) Configures prefix lifetimes.
valid-lifetime
The length of time that the prefix remains valid for the requesting router to use, in seconds. The range is from 60 to 4294967295. The default value is 2592000 seconds.
infinite
Indicates an unlimited lifetime.
preferred-lifetime
The length of time that the prefix remains preferred for the requesting router to use, in seconds. The range is from 60 to 4294967295. The default value is 604800 seconds.
at
Specifies absolute points in time where the prefix is no longer valid and no longer preferred.
date
The date for the valid lifetime to expire.
month
The month for the valid lifetime to expire.
year
The year for the valid lifetime to expire. The range is from 2003 to 2035.
time
The year for the valid lifetime to expire.
Command Default
The default time that the prefix remains valid is 2592000 seconds, and the default time that the prefix remains preferred for the requesting router to use is 604800 seconds.
Command History
Release
Modification
12.3(14)T
This command was introduced.
12.2(18)SXE
This command was integrated into Cisco IOS Release 12.2(18)SXE.
Cisco IOS XE Release 2.1
This command was integrated into Cisco IOS XE Release 2.1.
15.0(1)M
This command was modified. The default keyword was added and the command syntax was modified to show that lifetime can be configured only to a method-list.
Cisco IOS XE Release 2.5
This command was updated. It was integrated into Cisco IOS XE Release 2.5.
Usage Guidelines
In order for the Dynamic Host Configuration Protocol (DHCP) for IPv6 server to obtain prefixes from RADIUS servers, you must also configure the AAA client and Point-to-Point Protocol (PPP) on the router. For information on how to configure the AAA client and PPP, see the "Implementing ADSL and Deploying Dial Access for IPv6" module.
Use the aaa authorization configuration default, aaa group server radius, and radius-server host commands to specify a named list of authorization method and RADIUS servers to contact to acquire prefixes, and then apply that named list to the prefix-delegation aaa command.
Valid and preferred lifetimes can be specified for the prefixes assigned from AAA servers.
The prefix-delegation aaa and prefix-delegation pool commands are mutually exclusive in a pool.
Examples
The following example shows how to specify the use of a method list named list1:
Router> enable Router# configure terminal Router(config)# ipv6 dhcp pool name Router(config-dhcpv6)# prefix-delegation aaa method-list list1Related Commands
Command
Description
aaa authorization configuration default
Downloads static route configuration information from the AAA server using TACACS+ or RADIUS.
aaa group server radius
Groups different RADIUS server hosts into distinct lists and distinct methods.
prefix-delegation pool
Specifies a named IPv6 local prefix pool from which prefixes are delegated to DHCP for IPv6 clients.
radius-server host
Specifies a RADIUS server host.
sip address
Configures a SIP server IPv6 address to be returned in the SIP server’s IPv6 address list option to clients.
sip domain-name
Configures an SIP server domain name to be returned in the SIP server’s domain name list option to clients.
prefix-delegation pool
To specify a named IPv6 local prefix pool from which prefixes are delegated to Dynamic Host Configuration Protocol (DHCP) for IPv6 clients, use the prefix-delegation poolcommand in DHCP for IPv6 pool configuration mode. To remove a named IPv6 local prefix pool, use the no form of this command.
prefix-delegation pool poolname [ lifetime valid-lifetime preferred-lifetime ]
no prefix-delegation pool poolname
Syntax Description
poolname
User-defined name for the local prefix pool. The pool name can be a symbolic string (such as "Engineering") or an integer (such as 0).
lifetime
(Optional) Used to set a length of time for the hosts to remember router advertisements. If the optional lifetime keyword is configured, both valid and preferred lifetimes must be configured.
valid-lifetime
The amount of time that the prefix remains valid for the requesting router to use. The following values can be used:
- seconds --The length of time, in seconds, that the prefix remains valid for the requesting router to use. The range is from 60 through 4294967295. The preferred-lifetime value cannot exceed the valid-lifetime value.
- at --Specifies absolute points in time where the prefix is no longer valid and no longer preferred.
- infinite --Indicates an unlimited lifetime.
- valid-month valid-date valid-year valid-time --A fixed duration of time for hosts to remember router advertisements. The format to be used can be oct 24 2003 11:45 or 24 oct 2003 11:45.
preferred-lifetime
The length of time, in seconds, that the prefix remains preferred for the requesting router to use. The following values can be used:
- seconds --The length of time, in seconds, that the prefix remains valid for the requesting router to use. The range is from 60 through 4294967295. The preferred-lifetime value cannot exceed the valid-lifetime value.
- at --Specifies absolute points in time where the prefix is no longer valid and no longer preferred.
- infinite --Indicates an unlimited lifetime.
- preferred-month preferred-date preferred-year preferred-time-- A fixed duration of time for hosts to remember router advertisements. The format to be used can be oct 24 2003 11:45 or 24 oct 2003 11:45
Command Default
No IPv6 local prefix pool is specified. Valid lifetime is 2592000 seconds (30 days). Preferred lifetime is 604800 seconds (7 days).
Usage Guidelines
The prefix-delegation poolcommand specifies a named IPv6 local prefix pool from which prefixes are delegated to clients. Use the ipv6 local pool command to configure the named IPv6 prefix pool.
Optionally, valid and preferred lifetimes can be specified for the prefixes assigned from this pool. Users should coordinate the specified lifetimes with the lifetimes on prefixes from the upstream delegating router if the prefixes were acquired from that router.
The lifetimekeyword can be specified in one of two ways:
- A fixed duration that stays the same in consecutive advertisements.
- Absolute expiration time in the future so that advertised lifetime decrements in real time, which will result in a lifetime of 0 at the specified time in the future.
The specified length of time is from 60 to 4,294,967,295 seconds or infinity if the infinite keyword is specified.
The Cisco IOS DHCP for IPv6 server can assign prefixes dynamically from an IPv6 local prefix pool, which is configured using the ipv6 local pool command and associated with a DHCP for IPv6 configuration pool using the prefix-delegation pool command. When the server receives a prefix request from a client, it attempts to obtain unassigned prefixes, if any, from the pool.
After the client releases the previously assigned prefixes, the server will return the prefixes to the pool for reassignment to other clients.
Examples
The following example specifies that prefix requests should be satisfied from the pool called client-prefix-pool. The prefixes should be delegated with the valid lifetime set to 1800 seconds, and the preferred lifetime is set to 600 seconds:
prefix-delegation pool client-prefix-pool lifetime 1800 600Related Commands
Command
Description
ipv6 dhcp pool
Configures a DHCP for IPv6 pool and enters DHCP for IPv6 pool configuration mode.
ipv6 local pool
Configures a local IPv6 prefix pool.
prefix-delegation
Specifies a manually configured numeric prefix that is to be delegated to a particular client’s IAPD.
show ipv6 dhcp pool
Displays DHCP for IPv6 configuration pool information.
priority (firewall)
To specify a group priority and failover threshold value in a redundancy group, use the priority command in redundancy application group configuration mode. To disable the priority value of a group, use the no form of this command.
Usage Guidelines
The priority of the redundancy group is used to determine a redundancy group’s active or standby role on the configured node. The failover threshold is used to determine when a switchover must occur. After the priority is set under threshold, the active redundancy group gives up its role.
Examples
The following example shows how to configure the priority value and threshold value for the redundancy group named group1:
Router# configure terminal Router(config)# redundancy Router(config-red)# application redundancy Router(config-red-app)# group 1 Router(config-red-app-grp) priority 100 failover-threshold 90protocol
To define a protocol instance in a redundancy group, use the protocolcommand in redundancy application configuration mode. To remove the protocol instance from the redundancy group, use the no form of this command.
Usage Guidelines
Protocol configuration is used to configure timers and authentication method for a control interface. Thus, a protocol instance is attached to the control interface.
Examples
The following example shows how to configure a protocol named protocol 1 to a redundancy group:
Router# configure terminal Router(config)# redundancy Router(config-red)# application redundancy Router(config-red-app)# protocol 1 Router(config-red-app-prtcl)#Related Commands
Command
Description
application redundancy
Enters redundancy application configuration mode.
authentication
Configures clear text authentication and MD5 authentication for a redundancy group.
group
Enters redundancy application group configuration mode.
name
Configures the redundancy group with a name.
preempt
Enables preemption on the redundancy group.
timers hellotime
Configures timers for hellotime and holdtime messages for a redundancy group.
rbe nasip
To specify the IP address of an interface on the DHCP relay agent that will be sent to the DHCP server via the agent remote ID option, use the rbe nasip command in global configuration mode. To remove the specification, use the no form of this command.
Usage Guidelines
The rbe nasip command is used to configure support for the DHCP relay agent information option (option 82) for an ATM routed bridge encapsulation (RBE).
Support for the DHCP relay agent information option must be configured on the DHCP relay agent using the ip dhcp relay information option command for the rbe nasip command to be effective.
Examples
The following example shows how to enable support for DHCP option 82 on the DHCP relay agent by using the ip dhcp relay information option command. The rbe nasip command configures the router to forward the IP address for Loopback0 to the DHCP server. ATM RBE is configured on ATM subinterface 4/0.1.
ip dhcp-server 10.1.1.1 ! ip dhcp relay information option ! interface Loopback0 ip address 10.5.1.1 255.255.255.0 ! interface ATM 4/0 no ip address ! interface ATM 4/0.1 point-to-point ip unnumbered Loopback0 ip helper-address 10.1.1.1 atm route-bridged ip pvc 88/800 encapsulation aal5snap ! router eigrp 100 network 10.0.0.0 ! rbe nasip loopback 0redundancy
To enter redundancy configuration mode, use the redundancycommand in global configuration mode. This command does not have a no form.
Command History
Release
Modification
12.1(5)XV1
This command was introduced on the Cisco AS5800 universal access server.
12.2(4)XF
This command was introduced for the Cisco uBR10012 router.
12.2(11)T
This command was integrated into Cisco IOS Release 12.2(11)T.
12.0(9)SL
This command was integrated into Cisco IOS Release 12.0(9)SL.
12.0(16)ST
This command was implemented on the Cisco 7500 series Internet routers.
12.2(14)S
This command was integrated into Cisco IOS Release 12.2(14)S.
12.2(14)SX
Support for this command was added for the Supervisor Engine 720.
12.2(18)S
This command was implemented on the Cisco 7500 series Internet routers.
12.2(20)S
This command was implemented on the Cisco 7304 router.
12.2(17d)SXB
Support for this command on the Supervisor Engine 2 was extended to Release 12.2(17d)SXB.
12.3(7)T
This command was implemented on the Cisco 7500 series Internet routers.
12.2(8)MC2
This command was implemented on the MWR 1900 Mobile Wireless Edge Router (MWR).
12.3(11)T
This command was implemented on the MWR 1900 MWR.
12.3BC
This command was integrated into Cisco IOS Release 12.3BC.
12.0(22)S
This command was implemented on the Cisco 10000 series Internet routers.
12.2(18)SXE2
This command was integrated into Cisco IOS Release 12.2(18)SXE2.
12.2(28)SB
This command was integrated into Cisco IOS Release 12.2(28)SB.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(44)SQ
This command was integrated into Cisco IOS Release 12.2(44)SQ. Support for the Cisco RF Gateway 10 was added.
12.2(33) SRE
This command was modified. The interchassis subconfiguration mode was added.
Usage Guidelines
Use the redundancy command to enter redundancy configuration mode, where you can define aspects of redundancy such as shelf redundancy for the Cisco AS5800 universal access server.
Cisco 10000 Series Router
Before configuring line card redundancy, install the Y-cables. Before deconfiguring redundancy, remove the Y-cables.
The following restrictions apply to line card redundancy on the Cisco 10000 series router:
- Port-level redundancy is not supported.
- Redundant cards must occupy the two subslots within the same physical line card slot.
- The line card that will act as the primary line card must be the first line card configured, and it must occupy subslot 1.
Cisco 7600 Series Router
From redundancy configuration mode, you can enter the main CPU submode to manually synchronize the configurations that are used by the two supervisor engines.
From the main CPU submode, you can use the auto-sync command to use all the redundancy commands that are applicable to the main CPU.
To select the type of redundancy mode, use the mode command.
Nonstop forwarding (NSF) with stateful switchover (SSO) redundancy mode supports IPv4. NSF with SSO redundancy mode does not support IPv6, Internetwork Packet Exchange (IPX), and Multiprotocol Label Switching (MPLS).
After you enter redundancy configuration mode, you can use the interchassis command to specify the redundancy group number and enter interchassis redundancy mode. In the interchassis redundancy configuration mode, you can do the following:
- Specify a backbone interface for the redundancy group using the backbone command.
- Exit from interchassis configuration mode using the exit command.
- Specify the IP address of the remote redundancy group member using the member ip command.
- Specify the multichassis LACP (mLACP) node ID, system MAC address, and system priority using the node-id, system-mac, and system-priority commands.
- Define the peer monitoring method using the monitor command.
Cisco uBR10012 Universal Broadband Router
After you enter redundancy configuration mode, you can use the main-cpu command to enter main-CPU redundancy configuration mode, which allows you to specify which files are synchronized between the active and standby Performance Routing Engine (PRE) modules.
Cisco RF Gateway 10
At the redundancy configuration mode, you can do the following:
- Set a command to its default mode using the default command.
- Exit from a redundancy configuration using the exit command.
- Enter the line card group redundancy configuration using the linecard-group command.
- Enter main-CPU redundancy configuration mode using the main-cpu command, which allows you to specify which files are synchronized between the active and standby Supervisor cards.
- Configure the redundancy mode for the chassis using the mode command.
- Enforce a redundancy policy using the policy command.
Examples
The following example shows how to enable redundancy mode:
Router(config)# redundancy Router(config-red)#The following example shows how to assign the configured router shelf to the redundancy pair designated as 25. This command must be issued on both router shelves in the redundant router-shelf pair:
Router(config)# redundancy Router(config-red)# failover group-number 25Examples
The following example shows how to configure two 4-port channelized T3 half eight line cards that are installed in line card slot 2 for one-to-one redundancy:
Router(config)# redundancy Router(config-r)# linecard-group 1 y-cable Router(config-r-lc)# member subslot 2/1 primary Router(config-r-lc)# member subslot 2/0 secondaryExamples
The following example shows how to enter the main CPU submode:
Router(config)# redundancy Router(config-r)# main-cpu Router(config-r-mc)#Examples
The following example shows how to enter redundancy configuration mode and display the commands that are available in that mode on the Cisco uBR10012 router:
Router# configure terminal Router(config)# redundancy Router(config-r)# ? Redundancy configuration commands: associate Associate redundant slots exit Exit from redundancy configuration mode main-cpu Enter main-cpu mode no Negate a command or set its defaultsThe following example shows how to enter redundancy configuration mode and displays its associated commands on the Cisco RFGW-10 chassis:
Router# configure terminal Router(config)# redundancy Router(config-r)#? Redundancy configuration commands: default Set a command to its defaults exit Exit from redundancy configuration mode linecard-group Enter linecard redundancy submode main-cpu Enter main-cpu mode mode redundancy mode for this chassis no Negate a command or set its defaults policy redundancy policy enforcementThe following example shows how to enter redundancy configuration mode and its associated commands in the interchassis mode:
Router# configure terminal Router(config)# redundancyRouter(config-r)#?
Redundancy configuration commands: exit Exit from redundancy configuration mode interchassis Enter interchassis mode no Negate a command or set its defaults Router(config-r)# interchassis group 100 R1(config-r-ic)# ? Interchassis redundancy configuration commands: backbone specify a backbone interface for the redundancy group exit Exit from interchassis configuration mode member specify a redundancy group member mlacp mLACP interchassis redundancy group subcommands monitor define the peer monitoring method no Negate a command or set its defaultsRelated Commands
Command
Description
associate slot
Logically associates slots for APS processor redundancy.
auto-sync
Enables automatic synchronization of the configuration files in NVRAM.
clear redundancy history
Clears the redundancy event history log.
linecard-group y-cable
Creates a line card group for one-to-one line card redundancy.
main-cpu
Enters main-CPU redundancy configuration mode for synchronization of the active and standby PRE modules or Supervisor cards.
member subslot
Configures the redundancy role of a line card.
mode (redundancy)
Configures the redundancy mode of operation.
redundancy force-switchover
Switches control of a router from the active RP to the standby RP.
show redundancy
Displays information about the current redundant configuration and recent changes in states or displays current or historical status and related information on planned or logged handovers.
redundancy asymmetric-routing enable
To establish an asymmetric flow diversion tunnel for each redundancy group, use the redundancy asymmetric-routing enable command in interface configuration mode. To remove the established flow diversion tunnel, use the no form of this command.
Command Default
An asymmetric routing traffic diversion tunnel is not configured for redundancy groups.
Usage Guidelines
You must configure this command on a traffic interface that sends or receives asymmetric routing traffic. A tunnel is established between the traffic interface and the asymmetric routing interface for each redundancy group.
redundancy group
To configure fault tolerance for the mobile router, use the redundancy group command in mobile router configuration mode. To disable this functionality, use the no form of this command.
Usage Guidelines
The redundancy group command provides f ault tolerance by selecting one mobile router in the redundancy group name argument to provide connectivity for the mobile networks. This mobile router is in the active state. The other mobile routers are passive and wait until the active mobile router fails before a new active mobile router is selected. Only the active mobile router registers and sets up proper routing for the mobile networks. The redundancy state is either active or passive.
redundancy group (interface)
To enable the redundancy group (RG) traffic interface configuration, use the redundancy group command in interface configuration mode. To remove the redundancy group traffic interface configuration, use the no form of this command.
redundancy group id { ip virtual-ip | ipv6 { link-local-address | ipv6-address/prefix-length } | autoconfig } [ exclusive ] [ decrement value ]
no redundancy group id { ip | ipv6 { link-local-address | ipv6-address/prefix-length } }
Syntax Description
id
Redundancy group ID. Valid values are from 1 and 2.
ip virtual-ip
Enables IPv4 RGs and sets a virtual IPv4 address.
ipv6
Enables IPv6 RGs.
link-local-address
Link local address.
ipv6-address/prefix-length
IPv6 address and the length of the IPv6 prefix. IPv6 prefix is a decimal value that indicates how many of the high-order contiguous bits of the address comprise the prefix (the network portion of the address). A slash mark must precede the decimal value.
autoconfig
Obtains IP addresses through autoconfiguration.
exclusive
(Optional) Specifies whether the interface is exclusive to an RG.
decrement number
(Optional) Specifies the number that is decremented from the priority when the state of an interface goes down. The configured decrement value overrides the default number that is configured for an RG. Valid values are from 1 to 255.
Command History
Release
Modification
Cisco IOS XE Release 3.1S
This command was introduced.
15.2(3)T
This command was integrated into Cisco IOS Release 15.2(3)T.
Cisco IOS XE Release 3.7S
This command was modified. The virtual-ip, link-local-address, ipv6-address/prefix-length arguments and ip, ipv6, and autoconfig keywords were added.
Usage Guidelines
Use this command to configure a redundancy group for stateful switchover.
The virtual IP address and the physical address must be in the same subnet.
When autoconfiguration is enabled, the interface obtains an IP address automatically.
Examples
The following example shows how to enable the IPv6 redundancy group traffic interface configuration:
Device(config)# interface gigabitethernet 0/0/1 Device(config-if)# redundancy group 2 ipv6 FE80::260:3EFF:FE11:6770 exclusiveRelated Commands
Command
Description
control
Configures the control interface type and number for a redundancy group.
data
Configures the data interface type and number for a redundancy group.
interface
Configures an interface and enters interface configuration mode.
name
Configures the name of a redundancy group.
preempt
Enables preemption on a redundancy group.
protocol
Defines a protocol instance in a redundancy group.
redundancy rii
Configures an RII for a redundancy group.
relay agent information
To enter relay agent information option configuration mode, use the relay agent informationcommand in DHCP class configuration mode. To disable this functionality, use the no form of this command.
Usage Guidelines
If this command is omitted for Dynamic Host Configuration Protocol (DHCP) class-based address allocation, then the DHCP class matches to any relay agent information option, whether it is present or not.
Using the no relay agent information command removes all patterns in the DHCP class configured by the relay-information hex command.
Examples
The following example shows the relay information patterns configured for DHCP class 1.
ip dhcp class CLASS1 relay agent information relay-information hex 01030a0b0c02050000000123 relay-information hex 01030a0b0c02* relay-information hex 01030a0b0c02050000000000 bitmask 0000000000000000000000FF ip dhcp class CLASS2 relay agent informationrelay destination
To configure an IP address for a relay destination to which packets are forwarded by a Dynamic Host Configuration Protocol (DHCP) relay agent functioning as a DHCP server, use the relay destination command in DHCP pool configuration mode. To disable the IP address, use the no form of this command.
relay destination [ vrf vrf-name | global ] ip-address
no relay destination [ vrf vrf-name | global ] ip-address
Syntax Description
vrf
(Optional) Virtual routing and forwarding (VRF) instance that is associated with the relay destination address. The vrf-name argument specifies the name of the VRF table.
global
(Optional) IP address selected from the global address space. If the pool does not have any VRF configuration, then the relay destination address defaults to the global address space.
ip-address
IPv4 address of the remote DHCP server to which the DHCP client packets are relayed.
Usage Guidelines
The relay destination command serves the same function as the relay targetcommand, except that the relay target command specifies the DHCP server to which packets should be forwarded only for the class under which it is configured, and the relay destination command specifies the DHCP server to which packets should be forwarded for the pool itself. The relay target command overrides the relay destination command in cases in which the configured class name has been specified by the service gateway (SG).
When using the relay destination command, the ip-address argument is assumed to be in the same VRF as the address pool under which the command was configured. If the relay destination IP address is in a different VRF, or in the global address space, then the vrf vrf-name or global keywords need to be specified.
relay source
To configure an IP address for a relay source from which packets are forwarded by a Dynamic Host Configuration Protocol (DHCP) server, use the relay source command in DHCP-pool configuration mode. To disable the IP address, use the no form of this command.
relay target
To configure an IP address for a relay target to which packets are forwarded by a Dynamic Host Configuration Protocol (DHCP) server, use the relay targetcommand in DHCP pool class configuration mode. To disable the IP address, use the no form of this command.
relay target [ vrf vrf-name | global ] ip-address
no relay target [ vrf vrf-name | global ] ip-address
Syntax Description
vrf
(Optional) Configured virtual routing and forwarding (VRF) that is associated with the relay destination address. The vrf-name argument specifies the name of the VRF table.
Note If the vrf keyword is not specified, the target address is assumed to be in the same address space as the DHCP pool. If the vrf keyword is specified, the same VRF is assumed to apply here. However, if the target IP address is actually in the global address space, the global keyword should be specified.
global
(Optional) IP address selected from the global address space. If the pool does not have any VRF configuration, then the relay destination address defaults to the global address space.
ip-address
IPv4 address of the remote DHCP server to which the DHCP client packets are relayed.
Usage Guidelines
The relay target command serves the same function as the relay destination command, except that the relay target command specifies the DHCP server to which packets should be forwarded only for the class under which it is configured, and the relay destination command specifies the DHCP server to which packets should be forwarded for the pool itself. The relay target command overrides the relay destination command in cases in which the configured class name has been specified by the SG.
Examples
The following example shows how to configure a relay target if a service gateway (SG)-supplied class name is used to select a DHCP server to which packets are relayed:
ip dhcp pool abc1 relay source 10.0.0. 255.255.0.0. relay destination 10.5.1.1 class classname1 relay target 10.1.1.1 class classname2 relay target 10.2.2.2 class classname3In the above example, classname1 relays the DHCP DISCOVER packet to the server at 10.1.1.1, while classname2 relays the DHCP DISCOVER packet to the server at 10.2.2.2.
If the SG returned classname3, then the default pool at 10.5.1.1 is used. If the SG returns any other class name other than classname1, classname2, or classname3, then no relay action is taken.
The relay target configuration with respect to any configured DHCP pool works in the exact same way as a relay destination configuration works.
relay-information hex
To specify a hexadecimal string for the full relay agent information option, use the relay-information hex command in relay agent information option configuration mode. To remove the configuration, use the no form of this command.
relay-information hex pattern [*] [ bitmask mask ]
no relay-information hex pattern [*] [ bitmask mask ]
Usage Guidelines
The relay-information hex command sets a pattern that is used to match against defined DHCP classes. You can configure multiple relay-information hex commands for a DHCP class. This is useful to specify a set of relay information options that can not be summarized with a wildcard or a bitmask.
The pattern itself, excluding the wildcard, must contain a whole number of bytes (a byte is two hexadecimal numbers). For example, 010203 is 3 bytes (accepted) and 01020 is 2.5 bytes (not accepted).
If you omit this command, no pattern is configured and it is considered a match to any relay agent information value, but the relay information option must be present in the DHCP packet.
You must know the hexadecimal value of each byte location in option 82 to be able to configure the relay- information hex command. The option 82 format may vary from product to product. Contact the relay agent vendor for this information.
Examples
The following example shows the configured relay agent information patterns. Note that CLASS 2 has no pattern configured and will “match to any” class.
ip dhcp class CLASS1 relay agent information relay-information hex 01030a0b0c02050000000123 relay-information hex 01030a0b0c02* relay-information hex 01030a0b0c02050000000000 bitmask 0000000000000000000000FF ip dhcp class CLASS2 relay agent informationrelease dhcp
To perform an immediate release of a Dynamic Host Configuration Protocol (DHCP) lease for an interface, use the release dhcp command in user EXEC or privileged EXEC mode.
Usage Guidelines
The release dhcp command immediately releases the DHCP lease on the interface specified by the interface-typeand interface-numberarguments. If the router interface was not assigned a DHCP IP address by the DHCP server, the release dhcp command fails and displays the following error message:
Interface does not have a DHCP originated addressThis command does not have a no form.
Examples
The following example shows how to release a DHCP lease for an interface.
release dhcp ethernet 3/1Related Commands
Command
Description
ip address dhcp
Specifies that the Ethernet interface acquires an IP address through DHCP.
lease
Configures the duration of the lease for an IP address that is assigned from a Cisco IOS DHCP server to a DHCP client.
renew dhcp
Forces the renewal of the DHCP lease for the specified interface.
show dhcp lease
Displays the DHCP addresses leased from a server.
show interface
Displays statistics for all interfaces configured on the router or access server.
show ip dhcp binding
Displays address bindings on the Cisco IOS DHCP server.
show ip interface
Displays a summary of an interface’s IP information and status.
show running-config
Displays the contents of the currently running configuration file or the configuration for a specific interface.
show startup-config
Displays the contents of the configuration file that will be used at the next system startup.
remote command
To execute a Cisco 7600 series router command directly on the switch console or a specified module without having to log into the Cisco 7600 series router first, use the remote command command in privileged EXEC mode.
Command History
Release
Modification
12.2(14)SX
Support for this command was introduced on the Supervisor Engine 720.
12.2(17d)SXB
Support for this command on the Supervisor Engine 2 was extended to Release 12.2(17d)SXB.
12.2(18)SXD
The standby-rp keyword was added.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
Usage Guidelines
The module num keyword and argument designate the module number. Valid values depend on the chassis that is used. For example, if you have a 13-slot chassis, valid values are from 1 to 13. The module num keyword and argument are supported on DFC-equipped modules and the standby supervisor engine only.
When you execute the remote command switch command, the prompt changes to Switch-sp#.
This command is supported on DFC-equipped modules and the supervisor engine only.
This command does not support command completion, but you can use shortened forms of the command (for example, entering sh for show).
remote login
To access the Cisco 7600 router console or a specific module, use the remote login command in privileged EXEC mode.
Command History
Release
Modification
12.2(140SX
Support for this command was introduced on the Supervisor Engine 720.
12.2(17d)SXB
Support for this command on the Supervisor Engine 2 was extended to Release 12.2(17d)SXB.
12.2(18)SXD
This command was changed to include the standby-rp keyword.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
Usage Guidelines
Caution
When you enter the attach or remote login command to access another console from your switch, if you enter global or interface configuration mode commands, the switch might reset.
The module num keyword and argument designate the module number. Valid values depend on the chassis that is used. For example, if you have a 13-slot chassis, valid values are from 1 to 13. The module num keyword and argument are supported on DFC-equipped modules and the standby supervisor engine only.
When you execute the remote login module num command, the prompt changes to Router-dfcx# or Switch-sp#, depending on the type of module to which you are connecting.
When you execute the remote login standby-rp command, the prompt changes to Router-sdby#.
When you execute the remote login switch command, the prompt changes to Switch-sp#.
The remote login module num command is identical to the attach command.
There are two ways to end the session:
- You can enter the exit command as follows:
Switch-sp# exit [Connection to Switch closed by foreign host] Router#
- You can press Ctrl-C three times as follows:
Switch-sp# ^C Switch-sp# ^C Switch-sp# ^C Terminate remote login session? [confirm] y [Connection to Switch closed by local host] Router#Examples
This example shows how to perform a remote login to a specific module:
Router# remote login module 1 Trying Switch ... Entering CONSOLE for Switch Type "^C^C^C" to end this session Switch-sp#This example shows how to perform a remote login to the Cisco 7600 series router processor:
Router# remote login switch Trying Switch ... Entering CONSOLE for Switch Type "^C^C^C" to end this session Switch-sp#This example shows how to perform a remote login to the standby route processor:
Router# remote login standby-rp Trying Switch ... Entering CONSOLE for Switch Type "^C^C^C" to end this session Router-sdby#remote-ip (IPC transport-SCTP remote)
To define at least one IP address of the redundant peer that is used to communicate with the local device, use the remote-ipcommand in IPC transport-SCTP remote configuration mode. To remove one or all IP addresses from your configuration, use the no form of this command.
remote-ip peer-real-ip-address [peer-real-ip-address2]
no remote-ip peer-real-ip-address [peer-real-ip-address2]
Syntax Description
peer-real-ip-address
IP address of the remote peer.
The remote IP addresses must match the local IP addresses on the peer router. There can be either one or two IP addresses, which must be in the global Virtual Private Network (VPN) routing and forwarding (VRF). A virtual IP (VIP) address cannot be used.
peer-real-ip-address2
(Optional) IP address of the remote peer.
Usage Guidelines
Use the remote-ip command to help associate Stream Control Transmission Protocol (SCTP) as the transport protocol between the local and remote peer.
This command is part of a suite of commands used to configure the Stateful Switch Over (SSO) protocol. SSO is necessary for IP Security (IPSec) and Internet Key Exchange (IKE) to learn about the redundancy state of the network and to synchronize their internal application state with their redundant peers.
remote-port
To define the remote Stream Control Transmission Protocol (SCTP) port that is used to communicate with the redundant peer, use the remote-portcommand in SCTP protocol configuration mode.
Usage Guidelines
The remote-port command enters IPC transport-SCTP remote configuration mode, which allows you to specify at least one remote IP address (via the remote-ip command) that is used to communicate with the redundant peer.
remote-span
To configure a virtual local area network (VLAN) as a remote switched port analyzer (RSPAN) VLAN, use the remote-span command in config-VLAN mode. To remove the RSPAN designation, use the no form of this command.
Usage Guidelines
This command is not supported in the VLAN database mode.
You can enter the show vlan remote-span command to display the RSPAN VLANs in the Cisco 7600 series router.
renew deny unknown
To configure the renewal policy for unknown DHCP clients, use the renew deny unknowncommand in DHCP pool configuration mode. To disable the renewal policy, use the no form of this command.
Command Default
The DHCP server ignores a client request for an IP address that is not leased to the client.
Usage Guidelines
In some usage scenarios, such as a wireless hotspot, where both DHCP and secure ARP are configured, a connected client device might go to sleep or suspend for a period of time. If the suspended time period is greater than the secure ARP timeout (default of 91 seconds), but less than the DHCP lease time, the client can awake with a valid lease, but the secure ARP timeout has caused the lease binding to be removed because the client has been inactive. When the client awakes, the client still has a lease on the client side but is blocked from sending traffic. The client will try to renew its IP address but the DHCP server will ignore the request because the DHCP server has no lease for the client. The client must wait for the lease to expire before being able to recover and send traffic again.
To remedy this situation, use the renew deny unknown command in DHCP pool configuration mode. This command forces the DHCP server to reject renewal requests from clients if the requested address is present at the server but is not leased. The DHCP server sends a DHCPNAK denial message to the client, which forces the client back to its initial state. The client can then negotiate for a new lease immediately, instead of waiting for its old lease to expire.
Examples
The following example shows how to secure ARP table entries to DHCP leases. The renew deny unknown command allows the DHCP server to renew the lease of a DHCP client whose lease has been cleared because of a secure ARP timeout.
Router# configure terminal Router(config)# ip dhcp pool red Router(dhcp-config)# update arp Router(dhcp-config)# renew deny unknownrenew dhcp
To perform an immediate renewal of a Dynamic Host Configuration Protocol (DHCP) lease for an interface, use the renew dhcp command in user EXEC or privileged EXEC mode.
Usage Guidelines
The renew dhcp command immediately renews the DHCP lease for the interface specified by the interface-type and interface-number arguments. If the router interface was not assigned an IP address by the DHCP server, the renew dhcp command fails and displays the following error message:
Interface does not have a DHCP originated addressThis command does not have a no form.
Examples
The following example shows how to renew a DHCP lease for an interface:
renew dhcp Ethernet 3/1Related Commands
Command
Description
ip address dhcp
Specifies that the Ethernet interface acquires an IP address through DHCP.
lease
Configures the duration of the lease for an IP address that is assigned from a Cisco IOS DHCP server to a DHCP client.
release dhcp
Releases the DHCP lease on the specified interface.
show dhcp lease
Displays the DHCP addresses leased from a server.
show interface
Displays statistics for all interfaces configured on the router or access server.
show ip dhcp binding
Displays address bindings on the Cisco IOS DHCP server.
show ip interface
Displays a summary of an interface’s IP information and status.
show running-config
Displays the contents of the currently running configuration file or the configuration for a specific interface.
show startup-config
Displays the contents of the configuration file that will be used at the next system startup.
