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match reply prefix-list through utilization mark low
- match reply prefix-list
- match server access-list
- netbios-name-server
- netbios-node-type
- network (DHCP)
- next-server
- option
- origin
- override default-router
- override utilization high
- override utilization low
- preference (DHCPv6 Guard)
- relay agent information
- relay-information hex
- remote-span
- reserved-only
- show arp
- show hosts
- show ip arp
- show ip dhcp binding
- show ip dhcp conflict
- show ip dhcp database
- show ip dhcp import
- show ip dhcp pool
- show ip dhcp server statistics
- show ip dhcp snooping
- show ip dhcp snooping binding
- show ip dhcp snooping database
- show ip interface
- show ip route dhcp
- show ip source binding
- show ip verify source
- show ipv6 dhcp conflict
- trusted-port (DHCPv6 Guard)
- utilization mark high
- utilization mark low
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 ipv6acl1netbios-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.
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 172.16.3.252 172.16.3.253origin
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 30preference (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 254relay 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-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 informationremote-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.
reserved-only
To restrict address assignments from the Dynamic Host Configuration Protocol (DHCP) address pool only to the preconfigured reservations, use the reserved-only command in DHCP pool configuration mode. To disable the configuration, use the no form of this command.
Command Default
Address assignments from the DHCP address pool are not restricted only to the preconfigured reservations.
Usage Guidelines
When the DHCP port-based assignment feature is configured on multiple switches, devices connected to one switch may receive an IP address assignment from the neighboring switches rather than from the local DHCP address pool switch. If you want the switch to serve only the client directly connected to the switch, you can configure a group of switches with pools that share a common IP subnet but ignore the requests from other clients (not connected to this switch).
show arp
To display the entries in the Address Resolution Protocol (ARP) table, use the show arp command in user EXEC or privileged EXEC mode.
show arp [ [ vrf vrf-name ] [ [arp-mode] [ [ ip-address [mask] ] [ interface-type interface-number ] ] ] ] [detail]
Syntax Description
vrf vrf-name
(Optional) Displays the entries under the Virtual Private Network (VPN) routing and forwarding (VRF) instance specified by the vrf-name argument.
If this option is specified, it can be followed by any valid combination of the arp-mode, ip-address, mask, interface-type, and interface-number arguments and the detail keyword.
arp-mode
(Optional) Displays the entries that are in a specific ARP mode. This argument can be replaced by one of the following keywords:
- alias --Displays only alias ARP entries. An alias ARP entry is a statically configured (permanent) ARP table entry that is associated with a local IP address. This type of entry can be configured or removed using the arp (global) command with the alias keyword.
- dynamic --Displays only dynamic ARP entries. A dynamic ARP entry is learned through an ARP request and completed with the MAC address of the external host.
- incomplete --Displays only incomplete ARP entries. An incomplete ARP entry is learned through an ARP request but has not yet been completed with the MAC address of the external host.
- interface --Displaysonly interface ARP entries. An interface ARP entry contains a local IP address and is derived from an interface.
- static --Displays only static ARP entries. A static ARP entry is a statically configured (permanent) ARP entry that is associated with an external host. This type of entry can be configured or removed using the arp (global) command.
Note If this option is specified, it can be followed by any valid combination of the ip-address, mask, interface-type, and interface-number arguments and the detail keyword.
ip-address [mask]
(Optional) Displays the entries associated with a specific host or network.
Note If this option is specified, it can be followed by any valid combination of the interface-type and interface-number arguments and the detail keyword.
interface-type interface-number
(Optional) Displays the specified entries that are also associated with this router interface.
Note If this option is specified, it can be followed by the detail keyword.
detail
(Optional) Displays the specified entries with mode-specific details and information about subblocks (if any).
Command History
Release
Modification
10.0
This command was introduced.
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 the 12.2 SX release.
12.4(11)T
The vrf keyword and vrf-name argument were added to limit the display to entries under a specific VRF. The alias, dynamic, incomplete, interface, and static keywords were added to limit the display to entries in a specific ARP mode. The ip-address and mask arguments were added to limit the display to entries for a specific host or network. The interface-typeand interface-number arguments were added to limit the display to entries for a specific interface. The detail keyword was added to display additional details about the entries.
12.2(33)SRB
This command was integrated into Cisco IOS Release 12.2(33)SRB.
Usage Guidelines
To display all entries in the ARP cache, use this command without any arguments or keywords.
Entry Selection Options
You can to limit the scope of the command output by applying various combinations of the following ARP entry selection criteria:
- Entries under a specific VRF
- Entries in a specific ARP mode
- Entries for a specific host or entries for a specific network
- Entries associated with a specific router interface
Tip
The valid interface types and numbers can vary according to the router and the interfaces on the router. To list all the interfaces configured on a particular router, use the show interfaces command with the summary keyword. Use the appropriate interface specification, typed exactly as it is displayed under the Interface column of the show interfaces command output, to replace the interface-typeand interface-number arguments in the show arp command.
Detailed Output Format
To include additional details about each ARP entry displayed, use this command with the detail keyword. When this display option is used, the following additional information is included:
ARP Adjacency Notification
If Cisco Express Forwarding (CEF) is enabled on the router, the router maintains forwarding information (outbound interface and MAC header rewrite) for adjacent nodes. A node is said to be adjacent to another node if the node can be reached with a single hop across a link layer (Layer 2). CEF stores the forwarding information in an adjacency database so that Layer 2 addressing information can be inserted into link-layer headers attached to the ARP packets.
- To verify that IPv4 CEF is running, use the show ip cef command.
- To verify that an adjacency exists for a connected device, that the adjacency is valid, and that the MAC header rewrite string is correct, use the show adjacency command.
The ARP table information is one of the sources for CEF adjacency. Whenever the ARP subsystem attaches an ARP table entry to an outbound interface with a valid hardware address, the subsystem issues an internal “ARP adjacency” notification. The notification causes an ARP background process to synchronize that ARP entry with CEF adjacency via the adjacency database. If the synchronization succeeds, IP ARP adjacency is said to be “installed”; if the synchronization fails, IP ARP adjacency is said to have been “withdrawn.”
NoteAttachment to an outbound interface occurs only for ARP entries in the following modes: alias, dynamic, static, Application Simple, and Application Timer.
To display detailed information about any ARP adjacency notification that may have occurred, use the show arp command with the detail keyword. You can use this information to supplement the information available through ARP/CEF adjacency debug trace. To enable debug trace for ARP/CEF adjacency interactions, use the debug arp command with the adjacency keyword.
ARP Cache Administration
To refresh all entries for the specified interface (or all interfaces) or to refresh all entries of the specified address (or all addresses) in the specified VRF table (or in the global VRF table), use the clear arp-cache command.
To enable debugging output for ARP transactions, use the debug arp command.
Examples
The following is sample output from the show arp command with no optional keywords or arguments specified:
Router# show arp Protocol Address Age (min) Hardware Addr Type Interface Internet 192.0.2.112 120 0000.a710.4baf ARPA Ethernet3 AppleTalk 4028.5 29 0000.0c01.0e56 SNAP Ethernet2 Internet 192.0.2.114 105 0000.a710.859b ARPA Ethernet3 AppleTalk 4028.9 - 0000.0c02.a03c SNAP Ethernet2 Internet 192.0.2.121 42 0000.a710.68cd ARPA Ethernet3 Internet 192.0.2.9 - 0000.3080.6fd4 SNAP TokenRing0 AppleTalk 4036.9 - 0000.3080.6fd4 SNAP TokenRing0 Internet 192.0.2.9 - 0000.0c01.7bbd SNAP Fddi0The table below describes the fields shown in the display.
Table 1 show arp Field Descriptions Field
Description
Protocol
Protocol for network address in the Address field.
Address
The network address that corresponds to the Hardware Address.
Age (min)
Age in minutes of the cache entry. A hyphen (-) means the address is local.
Hardware Addr
LAN hardware address of a MAC address that corresponds to the network address.
Type
Indicates the encapsulation type the Cisco IOS software is using for the network address in this entry. Possible values include:
Interface
Indicates the interface associated with this network address.
When this command is used to display dynamic ARP entries, the display information includes the time of the last update and the amount of time before the next scheduled refresh is to occur. The following is sample output from the show arp command for the dynamic ARP entry at network address 192.0.2.1:
Router# show arp 192.0.2.1 detail ARP entry for 192.0.2.1, link type IP. Alias, last updated 13323 minutes ago. Encap type is ARPA, hardware address is 1234.1234.1234, 6 bytes long. ARP subblocks: * Static ARP Subblock Floating entry. Entry is complete, attached to GigabitEthernet1/1. * IP ARP Adjacency Adjacency (for 192.0.2.1 on GigabitEthernet1/1) was installed.When this command is used to display floating static ARP entries, the display information includes the associated interface, if any.The following is sample output from the show arp command for the floating static ARP entry at network address 192.0.2.2 whose intended interface is down:
Router# show arp 192.0.2.2 detail ARP entry for 192.0.2.2, link type IP. Alias, last updated 13327 minutes ago. Encap type is ARPA, hardware address is 1234.1234.1234, 6 bytes long. ARP subblocks: * Static ARP Subblock Floating entry. Entry is incomplete. * IP ARP Adjacency Adjacency (for 192.0.2.2 on GigabitEthernet1/1) was withdrawn.The following is sample detailed output from the show arp command for the Application Alias ARP entry at network address 192.0.2.3:
Router# show arp 192.0.2.3 detail ARP entry for 192.0.2.3, link type IP. Application Alias, via Ethernet2/2, last updated 0 minute ago. Created by "HSRP". Encap type is ARPA, hardware address is 0000.0c07.ac02, 6 bytes long. ARP subblocks: * Application Alias ARP Subblock * HSRP ARP Application entry for application HSRP.The following is sample detailed output from the show arp command for all dynamic ARP entries:
Router# show arp dynamic detail ARP entry for 192.0.2.4, link type IP. Dynamic, via Ethernet2/1, last updated 0 minute ago. Encap type is ARPA, hardware address is 0000.0000.0014, 6 bytes long. ARP subblocks: * Dynamic ARP Subblock Entry will be refreshed in 0 minute and 1 second. It has 1 chance to be refreshed before it is purged. Entry is complete. * IP ARP Adjacency Adjacency (for 192.0.2.4 on Ethernet2/1) was installed.Related Commands
Command
Description
arp (global)
Configures a permanent entry in the ARP cache.
clear arp-cache
Refreshes dynamically learned entries in the ARP cache.
debug arp
Enables debugging output for ARP packet transactions.
show adjacency
Verifies that an adjacency exists for a connected device, that the adjacency is valid, and that the MAC header rewrite string is correct.
show arp application
Displays ARP table information for a specific ARP application or for all applications supported by ARP and running on registered clients.
show arp ha
Displays the ARP HA status and statistics.
show arp summary
Displays the number of the ARP table entries of each mode.
show interfaces
Displays statistics for all interfaces configured on the router or access server.
show ip cef
Display entries in the FIB or to display a summary of the FIB.
show hosts
To display the default domain name, the style of name lookup service, a list of name server hosts, and the cached list of hostnames and addresses specific to a particular Domain Name System (DNS) view or for all configured DNS views, use the show hosts command in privileged EXEC mode.
Syntax Description
vrf vrf-name
(Optional) The vrf-name argument specifies the name of the Virtual Private Network (VPN) routing and forwarding (VRF) instance associated with the DNS view whose hostname cache entries are to be displayed. Default is the global VRF (that is, the VRF whose name is a NULL string) with the specified or default DNS view.
Note More than one DNS view can be associated with a VRF. To uniquely identify a DNS view, specify both the view name and the VRF with which it is associated.
view view-name
(Optional) The view-name argument specifies the DNS view whose hostname cache information is to be displayed. Default is the default (unnamed) DNS view associated with the specified or global VRF.
Note More than one DNS view can be associated with a VRF. To uniquely identify a DNS view, specify both the view name and the VRF with which it is associated.
default
(Optional) Displays the default view.
all
(Optional) Display all the host tables.
hostname
(Optional) The specified hostname cache information displayed is to be limited to entries for a particular hostname. Default is the hostname cache information for all hostname entries in the cache.
summary
(Optional) The specified hostname cache information is to be displayed in brief summary format. Disabled by default.
Command History
Release
Modification
10.0
This command was introduced.
12.2T
Support was added for Cisco modem user interface feature.
12.4(4)T
The vrf, all, and summary keywords and vrf-name and hostname arguments were added.
12.4(9)T
The view keyword and view-name argument were added.
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
This command displays the default domain name, the style of name lookup service, a list of name server hosts, and the cached list of hostnames and addresses specific to a particular DNS view or for all configured DNS views.
If you specify the show hosts command without any optional keywords or arguments, only the entries in the global hostname cache will be displayed.
If the output from this command extends beyond the bottom of the screen, press the Space bar to continue or press the Q key to terminate command output.
Examples
The following is sample output from the show hosts command with no parameters specified:
Router# show hosts Default domain is CISCO.COM Name/address lookup uses domain service Name servers are 192.0.2.220 Host Flag Age Type Address(es) EXAMPLE1.CISCO.COM (temp, OK) 1 IP 192.0.2.10 EXAMPLE2.CISCO.COM (temp, OK) 8 IP 192.0.2.50 EXAMPLE3.CISCO.COM (temp, OK) 8 IP 192.0.2.115 EXAMPLE4.CISCO.COM (temp, EX) 8 IP 192.0.2.111 EXAMPLE5.CISCO.COM (temp, EX) 0 IP 192.0.2.27 EXAMPLE6.CISCO.COM (temp, EX) 24 IP 192.0.2.30The following is sample output from the show hosts command that specifies the VRF vpn101:
Router# show hosts vrf vpn101 Default domain is example.com Domain list: example1.com, example2.com, example3.com Name/address lookup uses domain service Name servers are 192.0.2.204, 192.0.2.205, 192.0.2.206 Codes: UN - unknown, EX - expired, OK - OK, ?? - revalidate temp - temporary, perm - permanent NA - Not Applicable None - Not defined Host Port Flags Age Type Address(es) user None (perm, OK) 0 IP 192.0.2.001 www.example.com None (perm, OK) 0 IP 192.0.2.111 192.0.2.112The table below describes the significant fields shown in the display.
Table 2 show hosts Field Descriptions Field
Description
Default domain
Default domain name to be used to complete unqualified names if no domain list is defined.
Domain list
List of default domain names to be tried in turn to complete unqualified names.
Name/address lookup
Style of name lookup service.
Name servers
List of name server hosts.
Host
Learned or statically defined hostname. Statically defined hostname-to-address mappings can be added to the DNS hostname cache for a DNS view by using the ip hosts command.
Port
TCP port number to connect to when using the defined hostname in conjunction with an EXEC connect or Telnet command.
Flags
Indicates additional information about the hostname-to-IP address mapping. Possible values are as follows:
- EX--Entries marked EX are expired.
- OK--Entries marked OK are believed to be valid.
- perm--A permanent entry is entered by a configuration command and is not timed out.
- temp--A temporary entry is entered by a name server; the Cisco IOS software removes the entry after 72 hours of inactivity.
- ??--Entries marked ?? are considered suspect and subject to revalidation.
Age
Number of hours since the software last referred to the cache entry.
Type
Type of address. For example, IP, Connectionless Network Service (CLNS), or X.121.
If you have used the ip hp-host global configuration command, the show hosts command will display these hostnames as type HP-IP.
Address(es)
IP address of the host. One host may have up to eight addresses.
show ip arp
To display the Address Resolution Protocol (ARP) cache, where Serial Line Internet Protocol (SLIP) addresses appear as permanent ARP table entries, use the show ip arp EXEC command.
Usage Guidelines
ARP establishes correspondences between network addresses (an IP address, for example) and LAN hardware addresses (Ethernet addresses). A record of each correspondence is kept in a cache for a predetermined amount of time and then discarded.
Examples
The following is sample output from the show ip arp command:
Router# show ip arp Protocol Address Age(min) Hardware Addr Type Interface Internet 172.16.233.229 - 0000.0c59.f892 ARPA Ethernet0/0 Internet 172.16.233.218 - 0000.0c07.ac00 ARPA Ethernet0/0 Internet 172.16.233.19 - 0000.0c63.1300 ARPA Ethernet0/0 Internet 172.16.233.309 - 0000.0c36.6965 ARPA Ethernet0/0 Internet 172.16.168.11 - 0000.0c63.1300 ARPA Ethernet0/0 Internet 172.16.168.254 9 0000.0c36.6965 ARPA Ethernet0/0The table below describes the significant fields shown in the display.
Table 3 show ip arp Field Descriptions Field
Description
Protocol
Protocol for network address in the Address field.
Address
The network address that corresponds to the Hardware Address.
Age (min)
Age in minutes of the cache entry. A hyphen (-) means the address is local.
Hardware Addr
LAN hardware address of a MAC address that corresponds to the network address.
Type
Indicates the encapsulation type the Cisco IOS software is using the network address in this entry. Possible value include:
Interface
Indicates the interface associated with this network address.
show ip dhcp binding
To display address bindings on the Cisco IOS Dynamic Host Configuration Protocol (DHCP) server, use the show ip dhcp binding command in user EXEC or privileged EXEC mode.
Cisco IOS Release 12.0(1)T, 12.2(28)SB, and Later Releases
show ip dhcp binding [ip-address]
Cisco IOS Release 12.2(33)SRC and Later 12.2SR Releases
show ip dhcp binding [ vrf vrf-name ] [ip-address]
Syntax Description
ip-address
(Optional) IP address of the DHCP client for which bindings will be displayed. If the ip-address argument is used with the vrf vrf-name option, the binding in the specified VPN routing and forwarding (VRF) instance is displayed.
vrf vrf-name
(Optional) Specifies the name of a VRF instance.
Command History
Release
Modification
12.0(1)T
This command was introduced.
12.0(15)T
The command was modified. Support to display allocated subnets was added to the output.
12.2(28)SB
This command was integrated into Cisco IOS Release 12.2(28)SB.
12.2(33)SRC
This command was integrated into Cisco IOS Release 12.2(33)SRC. The vrf keyword and vrf-name argument were added.
12.2(33)SB9
This command was modified. The output was modified to display the option 82 suboptions of the remote ID and circuit ID.
Usage Guidelines
This command is used to display DHCP binding information for IP address assignment and subnet allocation. If a specific IP address is not specified, all address bindings are shown. Otherwise, only the binding for the specified client is displayed. The output that is generated for DHCP IP address assignment and subnet allocation is almost identical, except that subnet leases display an IP address followed by the subnet mask (which shows the size of the allocated subnet). Bindings for individual IP address display only an IP address and are not followed by a subnet mask.
Examples
IP Address Assignment Example
The following examples show the DHCP binding address parameters, including an IP address, an associated MAC address, a lease expiration date, the type of address assignment that has occurred, and the option 82 suboptions of the remote ID and circuit ID.
The table below describes the significant fields shown in the displays.
Router# show ip dhcp binding 192.0.2.2 IP address Client-ID/ Lease expiration Type Hardware address/ User name 192.0.2.2 aabb.cc00.0a00 Apr 28 2010 05:00 AM Automatic Remote id : 020a00001400006400000000
Table 4 show ip dhcp binding Field Descriptions Field
Description
IP address
The IP address of the host as recorded on the DHCP server.
Client-ID/Hardware address/User name
The MAC address or client ID of the host as recorded on the DHCP server.
Lease expiration
The lease expiration date and time of the IP address of the host.
Type
The manner in which the IP address was assigned to the host.
Remote id
Information sent to the DHCP server using a suboption of the remote ID.
Examples
Subnet Allocation Example
The following example shows the subnet lease to MAC address mapping, the lease expiration, and the lease type (subnet lease bindings are configured to be automatically created and released by default):
Router# show ip dhcp binding Bindings from all pools not associated with VRF: IP address Client-ID/ Lease expiration Type Hardware address/ User name 192.0.2.2/24 0063.6973.636f.2d64. Mar 29 2003 04:36 AM Automatic 656d.6574.6572.2d47. 4c4f.4241.4cThe table below describes the significant fields shown in the display.
Table 5 show ip dhcp binding Field Descriptions Field
Description
IP address
The IP address of the host as recorded on the DHCP server. The subnet that follows the IP address (/26) in the example defines this binding as a subnet allocation binding.
Hardware address
The MAC address or client identifier of the host as recorded on the DHCP server.
Lease expiration
The lease expiration date and time of the IP address of the host.
Type
The manner in which the IP address was assigned to the host.
show ip dhcp conflict
To display address conflicts found by a Dynamic Host Configuration Protocol (DHCP) server when addresses are offered to the client, use the show ip dhcp conflictcommandinuser EXEC or privileged EXEC mode.
Command Default
If you do not enter the IP address or VRF then all dhcp conflict related information is displayed.
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.
Cisco IOS XE Release 2.6
This command was modified. The vrf keyword and vrf-name argument were added.
Usage Guidelines
The server uses a ping operation to detect conflicts. The client uses gratuitous Address Resolution Protocol (ARP) to detect clients. If an address conflict is detected, the address is removed from the pool and the address is not assigned until an administrator resolves the conflict.
Examples
The following is sample output from the show ip dhcp conflict command, which shows the detection method and detection time for all IP addresses the DHCP server has offered that have conflicts with other devices:
Router# show ip dhcp conflict IP address Detection method Detection time VRF 172.16.1.32 Ping Feb 16 1998 12:28 PM vrf1 172.16.1.64 Gratuitous ARP Feb 23 1998 08:12 AM vrf2The table below describes the fields shown in the display.
Table 6 show ip dhcp conflict Field Descriptions Field
Description
IP address
The IP address of the host as recorded on the DHCP server.
Detection method
The manner in which the IP address of the hosts were found on the DHCP server. Can be a ping or a gratuitous ARP.
Detection time
The date and time when the conflict was found.
VRF
VRFs configured on the DHCP server.
The following is sample output from the show ip dhcp conflict vrf command:
Router# show ip dhcp conflict vrf vrf1 IP address Detection method Detection time VRF 172.16.1.32 Ping Feb 15 2009 05:39 AM vrf1See the table below for the field description.
Related Commands
Command
Description
clear ip dhcp conflict
Clears an address conflict from the Cisco IOS DHCP server database.
ip dhcp ping packets
Specifies the number of packets a Cisco IOS DHCP server sends to a pool address as part of a ping operation.
ip dhcp ping timeout
Specifies how long a Cisco IOS DHCP server waits for a ping reply from an address pool.
show ip dhcp database
To display Dynamic Host Configuration Protocol (DHCP) server database agent information, use the show ip dhcp database command in privileged EXEC mode.
Command Default
If a URL is not specified, all database agent records are shown. Otherwise, only information about the specified agent is displayed.
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.
Examples
The following example shows all DHCP server database agent information. The table below describes the significant fields shown in the display.
Router# show ip dhcp database URL : ftp://user:password@172.16.4.253/router-dhcp Read : Dec 01 1997 12:01 AM Written : Never Status : Last read succeeded. Bindings have been loaded in RAM. Delay : 300 seconds Timeout : 300 seconds Failures : 0 Successes : 1
Table 7 show ip dhcp database Field Descriptions Field
Description
URL
Specifies the remote file used to store automatic DHCP bindings. Following are the acceptable URL file formats:
Read
The last date and time bindings were read from the file server.
Written
The last date and time bindings were written to the file server.
Status
Indication of whether the last read or write of host bindings was successful.
Delay
The amount of time (in seconds) to wait before updating the database.
Timeout
The amount of time (in seconds) before the file transfer is aborted.
Failures
The number of failed file transfers.
Successes
The number of successful file transfers.
show ip dhcp import
To display the option parameters that were imported into the Dynamic Host Configuration Protocol (DHCP) server database, use the show ip dhcp import command in privileged EXEC command.
Command History
Release
Modification
12.1(2)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
Imported option parameters are not part of the router configuration and are not saved in NVRAM. Thus, the show ip dhcp import command is necessary to display the imported option parameters.
Examples
The following is sample output from the show ip dhcp import command:
Router# show ip dhcp import Address Pool Name:2 Domain Name Server(s): 10.1.1.1 NetBIOS Name Server(s): 10.3.3.3The following example indicates the address pool name:
Address Pool Name:2The following example indicates the imported values, which are domain name and NetBIOS name information:
Domain Name Server(s): 10.1.1.1 NetBIOS Name Server(s): 10.3.3.3show ip dhcp pool
To display information about the Dynamic Host Configuration Protocol (DHCP) address pools, use the show ip dhcp pool command in user EXEC or privileged EXEC mode.
Command History
Release
Modification
12.2(8)T
This command was introduced.
12.2(28)SB
This command was integrated into Cisco IOS Release 12.2(28)SB.
12.2(33)SRC
This command was modified. The command output was enhanced to display information about excluded addresses in network pools.
12.2(33)SXI4
This command was integrated into Cisco IOS Release 12.2(33)SXI4.
Usage Guidelines
Use this command to determine the subnets allocated and to examine the current utilization level for the pool or all the pools if the name argument is not used.
Examples
The following example shows DHCP address pool information for an on-demand address pool (ODAP), pool 1. The table below describes the significant fields shown in the display.
Router# show ip dhcp pool 1 Pool 1: Utilization mark (high/low) : 85 / 15 Subnet size (first/next) : 24 / 24 (autogrow) VRF name : abc Total addresses : 28 Leased addresses : 11 Pending event : none 2 subnets are currently in the pool : Current index IP address range Leased addresses 10.1.1.12 10.1.1.1 - 10.1.1.14 11 10.1.1.17 10.1.1.17 - 10.1.1.30 0 Interface Ethernet0/0 address assignment 10.1.1.1 255.255.255.248 10.1.1.17 255.255.255.248 secondaryThe following example shows DHCP address pool information for a network pool, pool 2. The table below describes the significant fields shown in the display.
Router# show ip dhcp pool 2 Pool pool2 : Utilization mark (high/low) : 80 / 70 Subnet size (first/next) : 0 / 0 Total addresses : 256 Leased addresses : 0 Excluded addresses : 2 Pending event : none 2 subnets are currently in the pool: Current index IP address range Leased/Excluded/Total 10.0.2.1 10.0.2.1 - 10.0.2.254 0 / 1 / 254 10.0.4.1 10.0.4.1 - 10.0.4.2 0 / 1 / 2
Table 8 show ip dhcp pool Field Descriptions Field
Description
Pool
The name of the pool.
Utilization mark (high/low)
The configured high and low utilization level for the pool.
Subnet size (first/next)
The size of the requested subnets.
VRF name
The VRF name to which the pool is associated.
Total addresses
The total number of addresses in the pool.
Leased addresses
The number of leased addresses in the pool.
Pending event
Displays any pending events.
2 subnets are currently in the pool
The number of subnets allocated to the address pool.
Current index
Displays the current index.
IP address range
The IP address range of the subnets.
Leased addresses
The number of leased addresses from each subnet.
Excluded addresses
The number of excluded addresses.
Interface Ethernet0/0 address assignment
The first line is the primary IP address of the interface. The second line is the secondary IP address of the interface. More than one secondary address on the interface is supported.
Related Commands
Command
Description
ip dhcp excluded-address
Specifies IP addresses that a DHCP server should not assign to DHCP clients.
ip dhcp pool
Configures a DHCP address pool on a DHCP server and enters DHCP pool configuration mode.
ip dhcp subscriber-id interface-name
Automatically generates a subscriber ID value based on the short name of the interface.
ip dhcp use subscriber-id client-id
Configures the DHCP server to globally use the subscriber identifier as the client identifier on all incoming DHCP messages.
show ip dhcp server statistics
To display Dynamic Host Configuration Protocol (DHCP) server statistics, use the show ip dhcp server statistics command in privileged EXEC mode.
show ip dhcp server statistics
Syntax in Cisco IOS Release 12.2(33)SRC and Subsequent 12.2SR Releases
show ip dhcp server statistics [ type number ]
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.
12.2(33)SRC
The type and number arguments were added. The command was enhanced to display interface level DHCP statistics.
Examples
The following example displays DHCP server statistics. The table below describes the significant fields in the display.
Router# show ip dhcp server statistics Memory usage 40392 Address pools 3 Database agents 1 Automatic bindings 190 Manual bindings 1 Expired bindings 3 Malformed messages 0 Secure arp entries 1 Renew messages 0 Message Received BOOTREQUEST 12 DHCPDISCOVER 200 DHCPREQUEST 178 DHCPDECLINE 0 DHCPRELEASE 0 DHCPINFORM 0 Message Sent BOOTREPLY 12 DHCPOFFER 190 DHCPACK 172 DHCPNAK 6
Table 9 show ip dhcp server statistics Field Descriptions Field
Description
Memory usage
The number of bytes of RAM allocated by the DHCP server.
Address pools
The number of configured address pools in the DHCP database.
Database agents
The number of database agents configured in the DHCP database.
Automatic bindings
The number of IP addresses that have been automatically mapped to the MAC addresses of hosts that are found in the DHCP database.
Manual bindings
The number of IP addresses that have been manually mapped to the MAC addresses of hosts that are found in the DHCP database.
Expired bindings
The number of expired leases.
Malformed messages
The number of truncated or corrupted messages that were received by the DHCP server.
Secure arp entries
The number of ARP entries that have been secured to the MAC address of the client interface.
Renew messages
The number of renew messages for a DHCP lease. The counter is incremented when a new renew message has arrived after the first renew message.
Message
The DHCP message type that was received by the DHCP server.
Received
The number of DHCP messages that were received by the DHCP server.
Sent
The number of DHCP messages that were sent by the DHCP server.
show ip dhcp snooping
To display the DHCP snooping configuration, use the show ip dhcp snoopingcommand in privileged EXEC mode.
Examples
This example shows how to display the DHCP snooping configuration:
Router# show ip dhcp snooping Switch DHCP snooping is enabled DHCP snooping is configured on following VLANs: 5 10 Insertion of option 82 is enabled Interface Trusted Rate limit (pps) -------------------- ------- ---------------- FastEthernet6/11 no 10 FastEthernet6/36 yes 50Related Commands
Command
Description
ip dhcp snooping
Globally enables DHCP snooping.
ip dhcp snooping binding
Sets up and generates a DHCP binding configuration to restore bindings across reboots.
ip dhcp snooping database
Configures the DHCP-snooping database.
ip dhcp snooping information option
Enables DHCP option 82 data insertion.
ip dhcp snooping limit rate
Configures the number of the DHCP messages that an interface can receive per second.
ip dhcp snooping packets
Enables DHCP snooping on the tunnel interface.
ip dhcp snooping verify mac-address
Verifies that the source MAC address in a DHCP packet matches the client hardware address on an untrusted port.
ip dhcp snooping vlan
Enables DHCP snooping on a VLAN or a group of VLANs.
show ip dhcp snooping binding
Displays the DHCP snooping binding entries.
show ip dhcp snooping database
Displays the status of the DHCP snooping database agent.
show ip dhcp snooping binding
To display the DHCP snooping binding entries, use the show ip dhcp snooping bindingcommand in privileged EXEC mode.
Syntax Description
ip-address
(Optional) IP address for the binding entries.
mac-address
(Optional) MAC address for the binding entries.
vlan vlan
(Optional) Specifies a valid VLAN number; valid values are from 1 to 4094.
interface type
(Optional) Specifies the interface type; possible valid values are ethernet, fastethernet, gigabitethernet, and tengigabitethernet.
number
Module and port number.
Command Default
If no argument is specified, the switch displays the entire DHCP snooping binding table.
Usage Guidelines
DHCP snooping is enabled on a VLAN only if both the global snooping and the VLAN snooping are enabled.
Examples
This example shows how to display the DHCP snooping binding entries for a switch:
Router# show ip dhcp snooping binding MacAddress IP Address Lease(seconds) Type VLAN Interface ----------- ----------- -------------- ------------- ----- -------------- 0000.0100.0201 10.0.0.1 600 dhcp-snooping 100 FastEthernet3/1This example shows how to display an IP address for DHCP snooping binding entries:
Router# show ip dhcp snooping binding 172.16.101.102 MacAddress IP Address Lease (seconds) Type VLAN Interface ----------- ----------- --------------- ------------- ----- ------------ 0000.0100.0201 172.16.101.102 1600 dhcp-snooping 100 FastEthernet3/1This example shows how to display the MAC address for the DHCP snooping binding entries:
Router# show ip dhcp snooping binding 10.5.5.2 0002.b33f.3d5f MacAddress IpAddress Lease(sec) Type VLAN Interface ------------------ --------- ---------- ------------- ---- ---------------- 00:02:B3:3F:3D:5F 10.5.5.2 492 dhcp-snooping 99 FastEthernet6/36 Router#This example shows how to display the DHCP snooping binding entries’ MAC address for a specific VLAN:
Router# show ip dhcp snooping binding 10.5.5.2 0002.b33f.3d5f vlan 99 MacAddress IpAddress Lease(sec) Type VLAN Interface ----------------- --------- ---------- ------------- ---- ---------------- 00:02:B3:3F:3D:5F 10.5.5.2 479 dhcp-snooping 99 FastEthernet6/36This example shows how to display the DHCP snooping binding entries on VLAN 100:
Router# show ip dhcp snooping binding vlan 100 MacAddress IP Address Lease(seconds) Type VLAN Interface -------------- ---------- -------------- ------------- ---- -------------- 0000.0100.0201 10.0.0.1 1600 dhcp-snooping 100 FastEthernet3/1This example shows how to display the DHCP snooping binding entries on Fast Ethernet interface 3/1:
Router# show ip dhcp snooping binding interface fastethernet3/1 MacAddress IP Address Lease(seconds) Type VLAN Interface -------------- ---------- -------------- ------------- ---- -------------- 0000.0100.0201 10.0.0.1 1600 dhcp-snooping 100 FastEthernet3/1The table below describes the fields in the show ip dhcp snooping command output.
Table 10 show ip dhcp snooping Command Output Field
Description
Mac Address
Client hardware MAC address.
IP Address
Client IP address assigned from the DHCP server.
Lease (seconds)
IP address lease time.
Type
Binding type; statically configured from CLI or dynamically learned.
VLAN
VLAN number of the client interface.
Interface
Interface that connects to the DHCP client host.
Related Commands
Command
Description
ip dhcp snooping
Globally enables DHCP snooping.
ip dhcp snooping binding
Sets up and generates a DHCP binding configuration to restore bindings across reboots.
ip dhcp snooping database
Configures the DHCP-snooping database.
ip dhcp snooping information option
Enables DHCP option 82 data insertion.
ip dhcp snooping limit rate
Configures the number of the DHCP messages that an interface can receive per second.
ip dhcp snooping packets
Enables DHCP snooping on the tunnel interface.
ip dhcp snooping verify mac-address
Verifies that the source MAC address in a DHCP packet matches the client hardware address on an untrusted port.
ip dhcp snooping vlan
Enables DHCP snooping on a VLAN or a group of VLANs.
show ip dhcp snooping
Displays the DHCP snooping configuration.
show ip dhcp snooping database
Displays the status of the DHCP snooping database agent.
show ip dhcp snooping database
To display the status of the DHCP snooping database agent, use the show ip dhcp snooping databasecommand in privileged EXEC mode.
Examples
This example shows how to display the DHCP snooping database:
Router# show ip dhcp snooping database Agent URL : Write delay Timer : 300 seconds Abort Timer : 300 seconds Agent Running : No Delay Timer Expiry : Not Running Abort Timer Expiry : Not Running Last Succeded Time : None Last Failed Time : None Last Failed Reason : No failure recorded. Total Attempts : 0 Startup Failures : 0 Successful Transfers : 0 Failed Transfers : 0 Successful Reads : 0 Failed Reads : 0 Successful Writes : 0 Failed Writes : 0 Media Failures : 0This example shows how to view additional operating statistics:
Router# show ip dhcp snooping database detail Agent URL : tftp://10.1.1.1/directory/file Write delay Timer : 300 seconds Abort Timer : 300 seconds Agent Running : No Delay Timer Expiry : 7 (00:00:07) Abort Timer Expiry : Not Running Last Succeded Time : None Last Failed Time : 17:14:25 UTC Sat Jul 7 2001 Last Failed Reason : Unable to access URL. Total Attempts : 21 Startup Failures : 0 Successful Transfers : 0 Failed Transfers : 21 Successful Reads : 0 Failed Reads : 0 Successful Writes : 0 Failed Writes : 21 Media Failures : 0 First successful access: Read Last ignored bindings counters : Binding Collisions : 0 Expired leases : 0 Invalid interfaces : 0 Unsupported vlans : 0 Parse failures : 0 Last Ignored Time : None Total ignored bindings counters: Binding Collisions : 0 Expired leases : 0 Invalid interfaces : 0 Unsupported vlans : 0 Parse failures : 0Related Commands
Command
Description
ip dhcp snooping
Globally enables DHCP snooping.
ip dhcp snooping binding
Sets up and generates a DHCP binding configuration to restore bindings across reboots.
ip dhcp snooping database
Configures the DHCP-snooping database.
ip dhcp snooping information option
Enables DHCP option 82 data insertion.
ip dhcp snooping limit rate
Configures the number of the DHCP messages that an interface can receive per second.
ip dhcp snooping packets
Enables DHCP snooping on the tunnel interface.
ip dhcp snooping verify mac-address
Verifies that the source MAC address in a DHCP packet matches the client hardware address on an untrusted port.
ip dhcp snooping vlan
Enables DHCP snooping on a VLAN or a group of VLANs.
show ip dhcp snooping
Displays the DHCP snooping configuration.
show ip dhcp snooping binding
Displays the DHCP snooping binding entries.
show ip interface
To display the usability status of interfaces configured for IP, use the show ip interface command in privileged EXEC mode.
Command History
Release
Modification
10.0
This command was introduced.
12.0(3)T
The command output was modified to show the status of the ip wccp redirect out and ip wccp redirect exclude add in commands.
12.2(14)S
The command output was modified to display the status of NetFlow on a subinterface.
12.2(15)T
The command output was modified to display the status of NetFlow on a subinterface.
12.3(6)
The command output was modified to identify the downstream VPN routing and forwarding (VRF) instance in the output.
12.3(14)YM2
The command output was modified to show the usability status of interfaces configured for Multiprocessor Forwarding (MPF) and implemented on the Cisco 7301 and Cisco 7206VXR routers.
12.2(14)SX
This command was implemented on the Supervisor Engine 720.
12.2(17d)SXB
This command was integrated into Cisco IOS 12.2(17d)SXB on the Supervisor Engine 2, and the command output was changed to include NDE for hardware flow status.
12.4(4)T
This command was integrated into Cisco IOS Release 12.4(4)T.
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(31)SB2
The command output was modified to display information about the Unicast Reverse Path Forwarding (RPF) notification feature.
12.4(20)T
The command output was modified to display information about the Unicast RPF notification feature.
12.2(33)SXI2
This command was modified. The command output was modified to display information about the Unicast RPF notification feature.
Cisco IOS XE Release 2.5
This command was modified. This command was implemented on the Cisco ASR 1000 Series Aggregation Services Routers.
Usage Guidelines
The Cisco IOS software automatically enters a directly connected route in the routing table if the interface is usable (which means that it can send and receive packets). If an interface is not usable, the directly connected routing entry is removed from the routing table. Removing the entry lets the software use dynamic routing protocols to determine backup routes to the network, if any.
If the interface can provide two-way communication, the line protocol is marked "up." If the interface hardware is usable, the interface is marked "up."
If you specify an optional interface type, information for that specific interface is displayed. If you specify no optional arguments, information on all the interfaces is displayed.
When an asynchronous interface is encapsulated with PPP or Serial Line Internet Protocol (SLIP), IP fast switching is enabled. A show ip interface command on an asynchronous interface encapsulated with PPP or SLIP displays a message indicating that IP fast switching is enabled.
You can use the show ip interface brief command to display a summary of the router interfaces. This command displays the IP address, the interface status, and other information.
The show ip interface brief command does not display any information related to Unicast RPF.
Examples
The following example shows configuration information for interface Gigabit Ethernet 0/3. In this example, the IP flow egress feature is configured on the output side (where packets go out of the interface), and the policy route map named PBRNAME is configured on the input side (where packets come into the interface).
Router# show running-config interface gigabitethernet 0/3 interface GigabitEthernet0/3 ip address 10.1.1.1 255.255.0.0 ip flow egress ip policy route-map PBRNAME duplex auto speed auto media-type gbic negotiation auto endThe following example shows interface information on Gigabit Ethernet interface 0/3. In this example, MPF is enabled, and both Policy Based Routing (PBR) and NetFlow features are not supported by MPF and are ignored.
Router# show ip interface gigabitethernet 0/3 GigabitEthernet0/3 is up, line protocol is up Internet address is 10.1.1.1/16 Broadcast address is 255.255.255.255 Address determined by setup command MTU is 1500 bytes Helper address is not set Directed broadcast forwarding is disabled Outgoing access list is not set Inbound access list is not set Proxy ARP is enabled Local Proxy ARP is disabled Security level is default Split horizon is enabled ICMP redirects are always sent ICMP unreachables are always sent ICMP mask replies are never sent IP fast switching is enabled IP fast switching on the same interface is disabled IP Flow switching is disabled IP CEF switching is enabled IP Feature Fast switching turbo vector IP VPN Flow CEF switching turbo vector IP multicast fast switching is enabled IP multicast distributed fast switching is disabled IP route-cache flags are Fast, CEF Router Discovery is disabled IP output packet accounting is disabled IP access violation accounting is disabled TCP/IP header compression is disabled RTP/IP header compression is disabled Policy routing is enabled, using route map PBR Network address translation is disabled BGP Policy Mapping is disabled IP Multi-Processor Forwarding is enabled IP Input features, "PBR", are not supported by MPF and are IGNORED IP Output features, "NetFlow", are not supported by MPF and are IGNOREDThe following example identifies a downstream VRF instance. In the example, "Downstream VPN Routing/Forwarding "D"" identifies the downstream VRF instance.
Router# show ip interface virtual-access 3 Virtual-Access3 is up, line protocol is up Interface is unnumbered. Using address of Loopback2 (10.0.0.8) Broadcast address is 255.255.255.255 Peer address is 10.8.1.1 MTU is 1492 bytes Helper address is not set Directed broadcast forwarding is disabled Outgoing access list is not set Inbound access list is not set Proxy ARP is enabled Local Proxy ARP is disabled Security level is default Split horizon is enabled ICMP redirects are always sent ICMP unreachables are always sent ICMP mask replies are never sent IP fast switching is enabled IP fast switching on the same interface is enabled IP Flow switching is disabled IP CEF switching is enabled IP Feature Fast switching turbo vector IP VPN CEF switching turbo vector VPN Routing/Forwarding "U" Downstream VPN Routing/Forwarding "D" IP multicast fast switching is disabled IP multicast distributed fast switching is disabled IP route-cache flags are Fast, CEF Router Discovery is disabled IP output packet accounting is disabled IP access violation accounting is disabled TCP/IP header compression is disabled RTP/IP header compression is disabled Policy routing is disabled Network address translation is disabled WCCP Redirect outbound is disabled WCCP Redirect inbound is disabled WCCP Redirect exclude is disabled BGP Policy Mapping is disabledThe following example shows the information displayed when Unicast RPF drop-rate notification is configured:
Router# show ip interface ethernet 2/3 Ethernet2/3 is up, line protocol is up Internet address is 10.0.0.4/16 Broadcast address is 255.255.255.255 Address determined by non-volatile memory MTU is 1500 bytes Helper address is not set Directed broadcast forwarding is disabled Outgoing access list is not set Inbound access list is not set Proxy ARP is enabled Local Proxy ARP is disabled Security level is default Split horizon is enabled ICMP redirects are always sent ICMP unreachables are always sent ICMP mask replies are never sent IP fast switching is disabled IP Flow switching is disabled IP CEF switching is disabled IP Null turbo vector IP Null turbo vector IP multicast fast switching is disabled IP multicast distributed fast switching is disabled IP route-cache flags are No CEF Router Discovery is disabled IP output packet accounting is disabled IP access violation accounting is disabled TCP/IP header compression is disabled RTP/IP header compression is disabled Probe proxy name replies are disabled Policy routing is disabled Network address translation is disabled WCCP Redirect outbound is disabled WCCP Redirect inbound is disabled WCCP Redirect exclude is disabled BGP Policy Mapping is disabledExamples
Unicast RPF Information
Input features: uRPF IP verify source reachable-via RX, allow default 0 verification drops 0 suppressed verification drops 0 verification drop-rate Router#The following example shows how to display the usability status for a specific VLAN:
Router# show ip interface vlan 1 Vlan1 is up, line protocol is up Internet address is 10.0.0.4/24 Broadcast address is 255.255.255.255 Address determined by non-volatile memory MTU is 1500 bytes Helper address is not set Directed broadcast forwarding is disabled Outgoing access list is not set Inbound access list is not set Proxy ARP is enabled Local Proxy ARP is disabled Security level is default Split horizon is enabled ICMP redirects are always sent ICMP unreachables are always sent ICMP mask replies are never sent IP fast switching is enabled IP fast switching on the same interface is disabled IP Flow switching is disabled IP CEF switching is enabled IP Fast switching turbo vector IP Normal CEF switching turbo vector IP multicast fast switching is enabled IP multicast distributed fast switching is disabled IP route-cache flags are Fast, CEF Router Discovery is disabled IP output packet accounting is disabled IP access violation accounting is disabled TCP/IP header compression is disabled RTP/IP header compression is disabled Probe proxy name replies are disabled Policy routing is disabled Network address translation is disabled WCCP Redirect outbound is disabled WCCP Redirect inbound is disabled WCCP Redirect exclude is disabled BGP Policy Mapping is disabled Sampled Netflow is disabled IP multicast multilayer switching is disabled Netflow Data Export (hardware) is enabledThe table below describes the significant fields shown in the display.
Table 11 show ip interface Field Descriptions Field
Description
Virtual-Access3 is up
Shows whether the interface hardware is usable (up). For an interface to be usable, both the interface hardware and line protocol must be up.
Broadcast address is
Broadcast address.
Peer address is
Peer address.
MTU is
MTU value set on the interface, in bytes.
Helper address
Helper address, if one is set.
Directed broadcast forwarding
Shows whether directed broadcast forwarding is enabled.
Outgoing access list
Shows whether the interface has an outgoing access list set.
Inbound access list
Shows whether the interface has an incoming access list set.
Proxy ARP
Shows whether Proxy Address Resolution Protocol (ARP) is enabled for the interface.
Security level
IP Security Option (IPSO) security level set for this interface.
Split horizon
Shows whether split horizon is enabled.
ICMP redirects
Shows whether redirect messages will be sent on this interface.
ICMP unreachables
Shows whether unreachable messages will be sent on this interface.
ICMP mask replies
Shows whether mask replies will be sent on this interface.
IP fast switching
Shows whether fast switching is enabled for this interface. It is generally enabled on serial interfaces, such as this one.
IP Flow switching
Shows whether Flow switching is enabled for this interface.
IP CEF switching
Shows whether Cisco Express Forwarding switching is enabled for the interface.
Downstream VPN Routing/Forwarding "D"
Shows the VRF instance where the PPP peer routes and AAA per-user routes are being installed.
IP multicast fast switching
Shows whether multicast fast switching is enabled for the interface.
IP route-cache flags are Fast
Shows whether NetFlow is enabled on an interface. Displays "Flow init" to specify that NetFlow is enabled on the interface. Displays "Ingress Flow" to specify that NetFlow is enabled on a subinterface using the ip flow ingresscommand. Shows "Flow" to specify that NetFlow is enabled on a main interface using the ip route-cache flow command.
Router Discovery
Shows whether the discovery process is enabled for this interface. It is generally disabled on serial interfaces.
IP output packet accounting
Shows whether IP accounting is enabled for this interface and what the threshold (maximum number of entries) is.
TCP/IP header compression
Shows whether compression is enabled.
WCCP Redirect outbound is disabled
Shows the status of whether packets received on an interface are redirected to a cache engine. Displays "enabled" or "disabled."
WCCP Redirect exclude is disabled
Shows the status of whether packets targeted for an interface will be excluded from being redirected to a cache engine. Displays "enabled" or "disabled."
Netflow Data Export (hardware) is enabled
NetFlow Data Expert (NDE) hardware flow status on the interface.
The following example shows how to display a summary of the usability status information for each interface:
Router# show ip interface brief Interface IP-Address OK? Method Status Protocol Ethernet0 10.108.00.5 YES NVRAM up up Ethernet1 unassigned YES unset administratively down down Loopback0 10.108.200.5 YES NVRAM up up Serial0 10.108.100.5 YES NVRAM up up Serial1 10.108.40.5 YES NVRAM up up Serial2 10.108.100.5 YES manual up up Serial3 unassigned YES unset administratively down downThe table below describes the significant fields shown in the display.
Table 12 show ip interface brief Field Descriptions Field
Description
Interface
Type of interface.
IP-Address
IP address assigned to the interface.
OK?
"Yes" means that the IP Address is valid. "No" means that the IP Address is not valid.
Method
The Method field has the following possible values:
- RARP or SLARP--Reverse Address Resolution Protocol (RARP) or Serial Line Address Resolution Protocol (SLARP) request.
- BOOTP--Bootstrap protocol.
- TFTP--Configuration file obtained from the TFTP server.
- manual--Manually changed by the command-line interface.
- NVRAM--Configuration file in NVRAM.
- IPCP--ip address negotiated command.
- DHCP--ip address dhcp command.
- unset--Unset.
- other--Unknown.
Status
Shows the status of the interface. Valid values and their meanings are:
Protocol
Shows the operational status of the routing protocol on this interface.
Related Commands
Command
Description
ip address
Sets a primary or secondary IP address for an interface.
ip vrf autoclassify
Enables VRF autoclassify on a source interface.
match ip source
Specifies a source IP address to match to required route maps that have been set up based on VRF connected routes.
route-map
Defines the conditions for redistributing routes from one routing protocol into another or to enable policy routing.
set vrf
Enables VPN VRF selection within a route map for policy-based routing VRF selection.
show ip arp
Displays the ARP cache, in which SLIP addresses appear as permanent ARP table entries.
show route-map
Displays static and dynamic route maps.
show ip route dhcp
To display the routes added to the routing table by the Dynamic Host Configuration Protocol (DHCP) server and relay agent, use the show ip route dhcp command in privileged EXEC configuration mode.
Command History
Release
Modification
12.2
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
To display information about global routes, use the show ip route dhcp command. To display routes in the VRF routing table, use the show ip route vrf vrf-name dhcp command.
Examples
The following is sample output from the show ip route dhcpcommand when entered without an address. This command lists all routes added by the DHCP server and relay agent.
Router# show ip route dhcp 10.5.5.56/32 is directly connected, ATM0.2 10.5.5.217/32 is directly connected, ATM0.2The following is sample output from the show ip route dhcp command when an address is specified. The output shows the details of the address with the server address (who assigned it) and the lease expiration time.
Router# show ip route dhcp 10.5.5.217 10.5.5.217 is directly connected, ATM0.2 DHCP Server: 10.9.9.10 Lease expires at Nov 08 2001 01:19 PMThe following is sample output from the show ip route vrf vrf-name dhcpcommand when entered without an address:
Router# show ip route vrf abc dhcp 10.5.5.218/32 is directly connected, ATM0.2The following is sample output from the show ip route vrf vrf-name dhcpcommand when an address is specified. The output shows the details of the address with the server address (who assigned it) and the lease expiration time.
Router# show ip route vrf red dhcp 10.5.5.218 10.5.5.218/32 is directly connected, ATM0.2 DHCP Server: 10.9.9.10 Lease expires at Nov 08 2001 03:15PMshow ip source binding
To display IP-source bindings configured on the system, use the show ip source command command in privileged EXEC mode.
show ip source binding [ip-address] [mac-address] [ dhcp-snooping | static ] [ vlan vlan-id ] [ interface type mod/port ]
Syntax Description
ip-address
(Optional) Binding IP address.
mac-address
(Optional) Binding MAC address.
dhcp-snooping
(Optional) Specifies DHCP snooping binding entry.
static
(Optional) Specifies a static binding entry.
vlan vlan-id
(Optional) Specifies the Layer 2 VLAN identification; valid values are from 1 to 4094.
interface type
(Optional) Interface type; possible valid values are fastethernet, gigabitethernet, tengigabitethernet, port-channel num, and vlan vlan-id.
mod / port
Module and port number.
Examples
This example shows the output without entering any keywords:
Router# show ip source binding
MacAddress IpAddress Lease(sec) Type VLAN Interface ------------------ --------------- ---------- ------------- ---- -------------------- 00:00:00:0A:00:0B 17.16.0.1 infinite static 10 FastEthernet6/10 00:00:00:0A:00:0A 17.16.0.2 10000 dhcp-snooping 10 FastEthernet6/11This example shows how to display the static IP binding entry for a specific IP address:
Router# show ip source binding 17.16.0.1 0000.000A.000B static vlan 10 interface gigabitethernet6/10 MacAddress IpAddress Lease(sec) Type VLAN Interface ------------------ --------------- ---------- ------------- ---- -------------------- 00:00:00:0A:00:0B 17.16.0.1 infinite static 10 FastEthernet6/10The table below describes the significant fields in the display.
Table 13 show ip source binding Field Descriptions Field
Description
MAC Address
Client hardware MAC address.
IP Address
Client IP address assigned from the DHCP server.
Lease (seconds)
IP address lease time.
Type
Binding type; static bindings configured from CLI to dynamic binding learned from DHCP snooping.
VLAN
VLAN number of the client interface.
Interface
Interface that connects to the DHCP client host.
show ip verify source
To display the IP source guard configuration and filters on a particular interface, use the show ip verify source command in EXEC mode.
Syntax Description
interface type
(Optional) Specifies the interface type; possible valid values are fastethernet, gigabitethernet, tengigabitethernet, port-channel num, and vlan vlan-id.
mod / port
Module and port number.
efp_id
(Optional) Specifies the Ethernet flow point (EFP) (service instance) ID.
efp_id
EFP number; range is 1 to 8000.
Usage Guidelines
Enable port security first because the DHCP security MAC filter cannot apply to the port or VLAN.
Examples
This example shows the display when DHCP snooping is enabled on VLANs 10 to 20, the interface has IP source filter mode that is configured as IP, and there is an existing IP address binding 10.0.0.1 on VLAN 10:
Router# show ip verify source interface gigabitethernet6/1 Interface Filter-type Filter-mode IP-address Mac-address Vlan --------- ----------- ----------- --------------- -------------- --------- gi6/1 ip active 10.0.0.1 10 gi6/1 ip active deny-all 11-20This example shows how to display the IP source guard configuration and filters on a specific interface:
Router# show ip verify source interface gigabitethernet6/1 Interface Filter-type Filter-mode IP-address Mac-address Vlan --------- ----------- ----------- --------------- -------------- --------- gi6/1 ip inactive-trust-portThis example shows the display when the interface does not have a VLAN enabled for DHCP snooping:
Router# show ip verify source interface gigabitethernet6/3 Interface Filter-type Filter-mode IP-address Mac-address Vlan --------- ----------- ----------- --------------- -------------- --------- gi6/3 ip inactive-no-snooping-vlanThis example shows the display when the interface has an IP source filter mode that is configured as IP MAC and an existing IP MAC binds 10.0.0.2/aaaa.bbbb.cccc on VLAN 10 and 10.0.0.1/aaaa.bbbb.cccd on VLAN 11:
Router# show ip verify source interface gigabitethernet6/4 Interface Filter-type Filter-mode IP-address Mac-address Vlan --------- ----------- ----------- --------------- -------------- --------- gi6/4 ip-mac active 10.0.0.2 aaaa.bbbb.cccc 10 gi6/4 ip-mac active 10.0.0.1 aaaa.bbbb.cccd 11 gi6/4 ip-mac active deny-all deny-all 12-20This example shows the display when the interface has an IP source filter mode that is configured as IP MAC and an existing IP MAC binding 10.0.0.3/aaaa.bbbb.ccce on VLAN 10, but port security is not enabled on the interface:
Router# show ip verify source interface gigabitethernet6/5 Interface Filter-type Filter-mode IP-address Mac-address Vlan --------- ----------- ----------- --------------- -------------- --------- gi6/5 ip-mac active 10.0.0.3 permit-all 10 gi6/5 ip-mac active deny-all permit-all 11-20This example shows the display when the interface does not have IP source filter mode configured:
Router# show ip verify source interface gigabitethernet6/6 DHCP security is not configured on the interface gi6/6.This example shows how to display all the interfaces on the switch that have DHCP snooping security enabled:
Router# show ip verify source Interface Filter-type Filter-mode IP-address Mac-address Vlan --------- ----------- ----------- --------------- -------------- --------- gi6/1 ip active 10.0.0.1 10 gi6/1 ip active deny-all 11-20 gi6/2 ip inactive-trust-port gi6/3 ip inactive-no-snooping-vlan gi6/4 ip-mac active 10.0.0.2 aaaa.bbbb.cccc 10 gi6/4 ip-mac active 11.0.0.1 aaaa.bbbb.cccd 11 gi6/4 ip-mac active deny-all deny-all 12-20 gi6/5 ip-mac active 10.0.0.3 permit-all 10 gi6/5 ip-mac active deny-all permit-all 11-20 Router#This example shows how to display all the interfaces on the switch that have DHCP snooping security enabled:
Router# show ip verify source interface gi5/0/0 efp_id 10 Interface Filter-type Filter-mode IP-address Mac-address Vlan EFP ID --------- ----------- ----------- --------------- ----------------- ---------- ---------- Gi5/0/0 ip-mac active 123.1.1.1 00:0A:00:0A:00:0A 100 10 Gi5/0/0 ip-mac active 123.1.1.2 00:0A:00:0A:00:0B 100 20 Gi5/0/0 ip-mac active 123.1.1.3 00:0A:00:0A:00:0C 100 30show ipv6 dhcp conflict
To display address conflicts found by a Dynamic Host Configuration Protocol for IPv6 (DHCPv6) server when addresses are offered to the client, use the show ipv6 dhcp conflict command in privileged EXEC mode.
Command History
Release
Modification
12.4(24)T
This command was introduced.
Cisco IOS XE Release 2.5
This command was integrated into Cisco IOS XE Release 2.5.
15.1(2)S
This command was modified. The vrf vrf-name keyword and argument were added.
Cisco IOS XE Release 3.3S
This command was modified. The vrf vrf-name keyword and argument were added.
Cisco IOS XE Release 3.2SE
This command was integrated into Cisco IOS XE Release 3.2SE.
Usage Guidelines
When you configure the DHCPv6 server to detect conflicts, it uses ping. The client uses neighbor discovery to detect clients and reports to the server through a DECLINE message. If an address conflict is detected, the address is removed from the pool, and the address is not assigned until the administrator removes the address from the conflict list.
trusted-port (DHCPv6 Guard)
To configure a port to become a trusted port, use the trusted-port command in Dynamic Host Configuration Protocol version 6 (DHCPv6) guard configuration mode. To disable this function, use the no form of this command.
Usage Guidelines
When the trusted-port command is enabled, messages received on ports that have this policy are not verified.
utilization mark high
To configure the high utilization mark of the current address pool size, use the utilization mark high command in DHCP pool configuration mode. To remove the high utilization mark, use the no form of this command.
Usage Guidelines
The current pool size is the sum of all addresses in all the subnets in the pool. If the utilization level exceeds the configured high utilization mark, the pool will schedule a subnet request.
This command can be used with both network and on-demand pools. However, in the case of a network pool, only the log option of this command can be used. In the case of an on-demand pool, the autogrow sizeoption of the origin command must be configured.
In certain network deployments, it is important for the network administrator to receive asynchronous notification when the DHCP pools are nearly exhausted so that preventive action can be taken. One common method for such notification is the generation of a system message.
If you use the log option, a system message can be generated for a DHCP pool when the pool utilization exceeds the configured high utilization threshold. A system message can also be generated when the pool's utilization is detected to be below the configured low utilization threshold.
Examples
The following example sets the high utilization mark to 80 percent of the current pool size:
utilization mark high 80The following pool configuration using the log keyword option generates a system message:
! ip dhcp pool abc utilization mark high 30 log utilization mark low 25 log network 10.1.1.0 255.255.255.248 !The following system message is generated when the second IP address is allocated from the pool:
00:02:01: %DHCPD-6-HIGH_UTIL: Pool "abc" is in high utilization state (2 addresses used out of 6). Threshold set at 30%.The following system message is generated when one of the two allocated IP addresses is returned to the pool:
00:02:58: %DHCPD-6-LOW_UTIL: Pool "abc" is in low utilization state (1 addresses used out of 6). Threshold set at 25%.utilization mark low
To configure the low utilization mark of the current address pool size, use the utilization mark low command in DHCP pool configuration mode. To remove the low utilization mark, use the no form of this command.
Usage Guidelines
The current pool size is the sum of all addresses in all the subnets in the pool. If the utilization level drops below the configured low utilization mark, a subnet release is scheduled from the address pool.
This command can be used with both network and on-demand pools. However, in the case of a network pool, only the log option of this command can be used. In the case of an on-demand pool, the autogrow sizeoption of the origin command must be configured.
In certain network deployments, it is important for the network administrator to receive asynchronous notification when the DHCP pools are nearly exhausted so that preventive action can be taken. One common method for such notification is the generation of a system message.
If you use the log option, a system message can be generated for a DHCP pool when the pool utilization exceeds the configured high utilization threshold. A system message can also be generated when the pool's utilization is detected to be below the configured low utilization threshold.
