To configure an interface as a protecting or a protected interface in a per-prefix loop-free alternative (LFA) repair path, use the
ipospffast-rerouteper-prefix command in interface configuration mode.
Specifies that the interface is protecting, that is, it can be used as the next hop in a repair path.
protection
Specifies that the interface is protected, that is, routes pointing to this interface can have a repair path.
disable
(Optional) Specifies that the interface is either protecting or protected.
Command Default
All interfaces are protected and protecting.
Command Modes
Interface configuration (config-if)#
Command History
Release
Modification
15.1(3)S
This command was introduced.
Cisco IOS XE Release 3.4S
This command was integrated into Cisco IOS XE Release 3.4S.
Usage Guidelines
If you know from the network topology that an interface cannot be used to reroute traffic (for example, if it goes to a customer site), you can use the
ipospffast-rerouteper-prefix command to disable it from being protecting interface.
Examples
The following example shows how to prohibit an interface from being a protecting interface:
Router(config)# interface Ethernet 0/0
ip address 192.0.2.1 255.255.255.0
ip ospf fast-reroute per-prefix candidate disable
Related Commands
Command
Description
debugipospffast-reroute
Displays debugging information for per-prefix LFA FRR paths.
fast-rerouteper-prefix(OSPF)
Configures a per-prefix l LFA route that redirects traffic to an alternative next hop other than the primary neighbor.
fast-reroutekeep-all-paths
Creates a list of all the candidate repair paths that were considered when a per-prefix LFA FRR oute was computed.
fast-reroutetie-break(OSPF)
Configures the tiebreaking policy in selecting in an LFA FRR repair path.
prefix-priority
Configures a set of prefixes to have high priority for protection in an OSPF local RIB.
showipospffast-reroute
Displays information about prefixes protected by LFA and IP FRR repair paths.
ip ospf flood-reduction
To suppress the unnecessary flooding of link-state advertisements (LSAs) in stable topologies, use the
ipospfflood-reduction command in interface configuration mode. To disable this feature, use the
no form of this command.
ipospfflood-reductionflood-reduction [disable]
noipospfflood-reduction
Syntax Description
disable
(Optional) Disables the suppressing of unnecessary flooding of LSAs in stable topologies.
Note
This keyword is available only in virtual network interface mode.
Command Default
This command is disabled by default.
Command Modes
Interface configuration (config-if)
Virtual network interface (config-if-vnet)
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.
Cisco IOS XE Release 3.2S
This command was modified. The
disable keyword was added. Support was added for this command in virtual network interface configuration mode.
15.0(1)SY
This command was modified. The
disable keyword was added. Support was added for this command in virtual network interface configuration mode.
15.1(1)SG
This command was integrated into Cisco IOS Release 15.1(1)SG.
Cisco IOS XE Release 3.3SG
This command was integrated into Cisco IOS XE Release 3.3SG.
Usage Guidelines
All routers supporting the Open Shortest Path First (OSPF) demand circuit are compatible and can interact with routers supporting flooding reduction.
If theipospfflood-reduction command is enabled for a virtual network and you want to disable it, use the
disable keyword in virtual network interface configuration mode.
Examples
The following example suppresses the flooding of unnecessary LSAs on serial interface 0:
interface serial 0
ip ospf flood-reduction
Related Commands
Command
Description
showipospfinterface
Displays OSPF-related interface information.
showipospfneighbor
Displays OSPF-neighbor information on a per-interface basis.
ip ospf hello-interval
To specify the interval between hello packets that the Cisco IOS software sends on the interface, use the
ipospfhello-interval command in interface configuration mode. To return to the default time, use the
noform of this command.
ipospfhello-intervalseconds
noipospfhello-interval
Syntax Description
seconds
Specifies the interval (in seconds). The value must be the same for all nodes on a specific network. The range is from 1 to 65535.
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 3.2S
This command was modified. Support was added for this command in virtual network interface configuration mode.
Usage Guidelines
This value is advertised in the hello packets. The smaller the hello interval, the faster topological changes will be detected, but more routing traffic will ensue. This value must be the same for all routers and access servers on a specific network.
Examples
The following example sets the interval between hello packets to 15 seconds:
interface ethernet 1
ip ospf hello-interval 15
Related Commands
Command
Description
ipospfdead-interval
Sets the time period for which hello packets must not have been seen before neighbors declare the router down.
ip ospf lls
To enable Link-Local Signaling (LLS) on an interface, regardless of the router-level LLS setting, use theipospfllscommand in interface configuration mode. To reconfigure the router-level LLS setting on the specific interface, use the no or defaultversion of this command.
ipospflls [disable]
{ no | default }
ipospflls [disable]
Syntax Description
no
Restores the default LLS setting for the interface that has been configured at the router level.
default
Inherits the global (router level) LLS settings for the interface that has been specified.
disable
(Optional) Disables LLS on a specified interface regardless of the global (router level) setting.
This command was integrated into Cisco IOS Release 12.3(7)T.
12.2(25)S
This command was integrated into Cisco IOS Release 12.2(25)S.
12.2(18)SXE
This command was integrated into Cisco IOS Release 12.2(18)SXE.
12.2(27)SBC
This command was integrated into Cisco IOS Release 12.2(27)SBC.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
Cisco IOS XE Release 3.2S
This command was modified. Support was added for this command in virtual network interface configuration mode.
Usage Guidelines
By default, each Open Shortest Path First (OSPF) interface inherits the LLS setting from the router level. The ipospflls interface-level command takes precedence over the capabilitylls router-level command. For example, if you have entered the nocapabilitylls command to disable LLS at the router level, you can use the ipospflls command to selectively enable LLS for specific interfaces, in order to allow the router to enable OSPF nonstop forwarding (NSF) awareness only for these specified interfaces.
To unconfigure the interface LLS setting, enter either the defaultipospflls command or the noipospflls command to restore the default LLS setting for the interface that has been configured at the router level. For example, if the capabilitylls command is enabled (by default) at the router level, you can use either the defaultipospflls command or the noipospflls command to disable LLS on specific interfaces, for instance, to interoperate on network segments where there are routers that do not properly handle LLS.
Note
If the network is running OSPF with the LLS feature enabled by default, LLS is globally enabled for all interfaces. If a router in the network is connected to a non-Cisco device that is not in compliance with RFC 2328, there may be network difficulties involving the forming of OSPF neighbors. In this situation, we recommend that you use the ipospflls command with the disable keyword to disable LLS on the router that is connected to the non-Cisco device.
Examples
In following example, LLS is disabled on Ethernet interface 2/0:
Router(config)# interface Ethernet2/0
Router(config-if)# ip address 10.1.145.2 255.255.0.0
Router(config-if)# no ip directed-broadcast
Router(config-if)# ip ospf message-digest-key 1 md5 testing
Router(config-if)# ip ospf lls disable
Related Commands
Command
Description
capabilitylls
Enables the use of the LLS data block in originated OSPF packets and reenables OSPF NSF awareness.
showipospfinterface
Displays OSPF-related interface information.
ip ospf message-digest-key md5
To enable Open Shortest Path First (OSPF) Message Digest 5 (MD5) authentication, use the
ipospfmessage-digest-keymd5command in interface configuration mode. To remove an old MD5 key, use the
noform of this command.
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 3.2S
This command was modified. Support was added for this command in virtual network interface configuration mode.
Usage Guidelines
Usually, one key per interface is used to generate authentication information when sending packets and to authenticate incoming packets. The same key identifier on the neighbor router must have the same
key value.
The process of changing keys is as follows. Suppose the current configuration is as follows:
interface ethernet 1
ip ospf message-digest-key 100 md5 OLD
You change the configuration to the following:
interface ethernet 1
ip ospf message-digest-key 101 md5 NEW
The system assumes its neighbors do not have the new key yet, so it begins a rollover process. It sends multiple copies of the same packet, each authenticated by different keys. In this example, the system sends out two copies of the same packet--the first one authenticated by key 100 and the second one authenticated by key 101.
Rollover allows neighboring routers to continue communication while the network administrator is updating them with the new key. Rollover stops once the local system finds that all its neighbors know the new key. The system detects that a neighbor has the new key when it receives packets from the neighbor authenticated by the new key.
After all neighbors have been updated with the new key, the old key should be removed. In this example, you would enter the following:
interface ethernet 1
no ip ospf message-digest-key 100
Then, only key 101 is used for authentication on Ethernet interface 1.
We recommend that you not keep more than one key per interface. Every time you add a new key, you should remove the old key to prevent the local system from continuing to communicate with a hostile system that knows the old key. Removing the old key also reduces overhead during rollover.
Note
If theservicepassword-encryption command is not used when implementing OSPF MD5 authentication, the MD5 secret will be stored as plain text in NVRAM.
Examples
The following example sets a new key 19 with the password
8ry4222:
interface ethernet 1
ip ospf message-digest-key 10 md5 xvv560qle
ip ospf message-digest-key 19 md5 8ry4222
Related Commands
Command
Description
areaauthentication
Enables authentication for an OSPF area.
ipospfauthentication
Specifies authentication type for an interface.
servicepassword-encryption
Encrypts a password.
ip ospf mtu-ignore
To disable Open Shortest Path First (OSPF) maximum transmission unit (MTU) mismatch detection on receiving database descriptor (DBD) packets, use the
ipospfmtu-ignore command in interface configuration mode. To enable OSPF mismatch detection, use the
noform of this command.
ipospfmtu-ignore [disable]
noipospfmtu-ignore
Syntax Description
disable
(Optional) Causes OSPF MTU mismatch detection to occur because OSPF MTU mismatch detection is being disabled.
Note
This keyword is available only in virtual network interface mode.
Command Default
OSPF MTU mismatch detection is enabled.
Command Modes
Interface configuration (config-if)
Virtual network interface (config-if-vnet)
Command History
Release
Modification
12.0(3)
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 3.2S
This command was modified. The
disable keyword was added. Support was added for this command in virtual network interface configuration mode.
15.0(1)SY
This command was modified. The
disable keyword was added. Support was added for this command in virtual network interface configuration mode.
15.1(1)SG
This command was integrated into Cisco IOS Release 15.1(1)SG.
Cisco IOS XE Release 3.3SG
This command was integrated into Cisco IOS XE Release 3.3SG.
15.3(2)T
This command was integrated into Cisco IOS Release 15.3(2)T.
Usage Guidelines
OSPF checks whether neighbors are using the same MTU on a common interface. This check is performed when neighbors exchange DBD packets. If the receiving MTU in the DBD packet is higher than the IP MTU configured on the incoming interface, OSPF adjacency will not be established.
If theipospfmtu-ignore command is enabled for a virtual network and you want to disable it, use the
disable keyword in virtual network interface configuration mode.
Examples
The following example disables OSPF MTU mismatch detection on receiving DBD packets:
interface serial 0/0
ip ospf mtu-ignore
ip ospf multi-area
To configure multiarea adjacency on a interface that is configured with Open Shortest Path First (OSPF), use the ipospfmulti-area command in interface configuration mode. To disable multiarea adjacency, use the no form of this command.
ipospfmulti-areamulti-area-id
noipospfmulti-areamulti-area-id
Syntax Description
multi-area-id
Identifier of the area for which authentication is to be enabled. The identifier can be specified as an IP address or a decimal value. The range is from 0 to
4294967295.
Command Default
No OSPF multiarea adjacency interface is defined.
Command Modes
Interface configuration (config-if)
Command History
Release
Modification
Cisco IOS Release XE 3.10S
This command was introduced.
Examples
The following example shows how to configure OSPF multiarea adjacency on an interface with an area identifier of 1:
Specifies the cost of sending a packet on an OSPF multiarea interface.
show ip ospf interface
Displays the interface information related to OSPF.
ip ospf multi-area cost
To specify the cost of sending a packet on an Open Shortest Path First (OSPF) multiarea interface, use the ip ospf multi-area cost command in interface configuration mode. To reset the multiarea path cost to the default value, use the no form of this command.
ipospfmulti-areamulti-area-idcostinterface-cost
noipospfmulti-areamulti-area-idcostinterface-cost
Syntax Description
multi-area-id
Identifier of the area for which authentication is to be enabled. The identifier can be specified as an IP address or a decimal value. The range is from 0 to 4294967295.
interface-cost
Unsigned integer value expressed as the link-state metric. The range is from 1 to 65535.
Command Default
No interface cost is defined for OSPF multiarea adjacency.
Command Modes
Interface configuration (config-if)
Command History
Release
Modification
Cisco IOS Release XE 3.10S
This command was introduced.
Examples
The following example shows how to set the OSPF multiarea interface cost value to 65:
Enables multiarea adjacency on the OSPF interface.
showipospfinterface
Displays the interface information related to OSPF.
ip ospf name-lookup
To configure Open Shortest Path First (OSPF) to look up Domain Name System (DNS) names for use in all OSPF
show EXEC command displays, use the
ipospfname-lookup command in global configuration mode. To disable this function, use the
noform of this command.
ipospfname-lookup
noipospfname-lookup
Syntax Description
This command has no arguments or keywords.
Command Default
This command is disabled by default.
Command Modes
Global configuration
Command History
Release
Modification
10.0
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
This command makes it easier to identify a router because the router is displayed by name rather than by its router ID or neighbor ID.
Examples
The following example configures OSPF to look up DNS names for use in all OSPF
show EXEC command displays:
ip ospf name-lookup
ip ospf network
To configure the Open Shortest Path First (OSPF) network type to a type other than the default for a given medium, use the
ipospfnetwork command in interface configuration mode. To return to the default value, use the
noform of this command.
Sets the network type to nonbroadcast multiaccess (NBMA).
point-to-multipointnon-broadcast
Sets the network type to point-to-multipoint. The optional
non-broadcast keyword sets the point-to-multipoint network to be nonbroadcast. If you use the
non-broadcast keyword, the
neighbor command is required.
The
non-broadcast keyword used with the
point-to-multipoint keyword was 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.
Cisco IOS XE Release 3.2S
This command was modified. Support was added for this command in virtual network interface configuration mode.
Usage Guidelines
Using this feature, you can configure broadcast networks as NBMA networks when, for example, routers in your network do not support multicast addressing. You can also configure nonbroadcast multiaccess networks (such as X.25, Frame Relay, and Switched Multimegabit Data Service (SMDS)) as broadcast networks. This feature saves you from needing to configure neighbors.
Configuring NBMA networks as either broadcast or nonbroadcast assumes that there are virtual circuits from every router to every router or fully meshed networks. However, there are other configurations where this assumption is not true. For example, a partially meshed network. In these cases, you can configure the OSPF network type as a point-to-multipoint network. Routing between two routers that are not directly connected will go through the router that has virtual circuits to both routers. You need not configure neighbors when using this feature.
If this command is issued on an interface that does not allow it, this command will be ignored.
OSPF has two features related to point-to-multipoint networks. One feature applies to broadcast networks; the other feature applies to nonbroadcast networks:
On point-to-multipoint, broadcast networks, you can use the
neighbor command, and you must specify a cost to that neighbor.
On point-to-multipoint, nonbroadcast networks, you must use the
neighbor command to identify neighbors. Assigning a cost to a neighbor is optional.
Examples
The following example sets your OSPF network as a broadcast network:
interface serial 0
ip address 192.168.77.17 255.255.255.0
ip ospf network broadcast
encapsulation frame-relay
The following example illustrates a point-to-multipoint network with broadcast:
interface serial 0
ip address 10.0.1.1 255.255.255.0
encapsulation frame-relay
ip ospf cost 100
ip ospf network point-to-multipoint
frame-relay map ip 10.0.1.3 202 broadcast
frame-relay map ip 10.0.1.4 203 broadcast
frame-relay map ip 10.0.1.5 204 broadcast
frame-relay local-dlci 200
!
router ospf 1
network 10.0.1.0 0.0.0.255 area 0
neighbor 10.0.1.5 cost 5
neighbor 10.0.1.4 cost 10
Related Commands
Command
Description
frame-relaymap
Defines mapping between a destination protocol address and the DLCI used to connect to the destination address.
neighbor(OSPF)
Configures OSPF routers interconnecting to nonbroadcast networks.
x25map
Sets up the LAN protocols-to-remote host mapping.
ip ospf prefix-suppression
To prevent Open Shortest Path First (OSPF) from advertising all IP prefixes that belong to a specific interface, except for prefixes that are associated with secondary IP addresses, use the ipospf prefix-suppression command in interface configuration mode. To remove the per-interface configuration from the interface and allow the interface to inherit the IP prefix suppression setting from the router configuration, use the no form of this command.
ipospfprefix-suppression [disable]
noipospfprefix-suppression
Syntax Description
disable
(Optional) Specifies that OSPF will advertise the interface IP prefix, regardless of the router mode configuration for IP prefix suppression.
Command Default
All IP prefixes that are associated with the interface are advertised.
Command Modes
Interface configuration (config-if)
Command History
Release
Modification
12.4(15)T
This command was introduced.
Cisco IOS XE Release 2.6
This command was integrated into Cisco IOS XE Release 2.6
Usage Guidelines
You can suppress IP prefixes on a per-interface basis for all interface types by entering the ipospfprefix-suppression command in interface configuration mode.
When the ipospfprefix-suppression command is configured, it takes precedence over the prefix-suppression router configuration command. If the prefix-suppression router configuration command has been entered, the interfaces for the specified OSPF process will inherit the prefix suppression setting from the router configuration command.
When you enter the ipospfprefix-suppression command, prefix generation for any interface type, including loopbacks and passive interfaces, is suppressed. Only prefixes associated with secondary IP addressees remain unaffected.
Examples
The following example suppresses all IP prefixes, except for those associated with secondary IP addresses, for GigabitEthernet interface 1/1/1:
interface gigabitethernet 1/1/1
ip ospf prefix-suppression
Related Commands
Command
Description
prefix-suppression
Prevents OSPF from advertising all IP prefixes except prefixes that are associated with loopbacks, secondary IP addresses, and passive interfaces for a specific OSPF process.
ip ospf priority
To set the router priority, which helps determine the designated router for this network, use the
ipospfpriority command in interface configuration mode. To return to the default value, use the
noform of this command.
ipospfprioritynumber-value
noipospfpriority
Syntax Description
number-value
A number value that specifies the priority of the router. The range is from 0 to 255.
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 3.2S
This command was modified. Support was added for this command in virtual network interface configuration mode.
Usage Guidelines
When two routers attached to a network both attempt to become the designated router, the one with the higher router priority takes precedence. If there is a tie, the router with the higher router ID takes precedence. A router with a router priority set to zero is ineligible to become the designated router or backup designated router. Router priority is configured only for interfaces to multiaccess networks (in other words, not to point-to-point networks).
This priority value is used when you configure Open Shortest Path First (OSPF) for nonbroadcast networks using the
neighbor router configuration command for OSPF.
Examples
The following example sets the router priority value to 4:
interface ethernet 0
ip ospf priority 4
Related Commands
Command
Description
ipospfnetwork
Configures the OSPF network type to a type other than the default for a given medium.
neighbor(OSPF)
Configures OSPF routers interconnecting to nonbroadcast networks.
ip ospf resync-timeout
To configure how long the router will wait before taking a neighbor adjacency down if the out-of-band resynchronization (oob-resync) has not taken place since the time a restart signal (Open Shortest Path First [OSPF] hello packet with RS-bit set) was received from the neighbor, use the ipospfresync-timeoutcommand in interface configuration mode. To restore the default value, use the no form of this command.
ipospfresync-timeoutseconds
noipospfresync-timeout
Syntax Description
seconds
Number of seconds the router will wait before taking a neighbor adjacency down if the out-of-band resynchronization (oob-resync) has not taken place since the time a restart signal (OSPF hello packet with RS-bit set) was received from the neighbor. The value is in the range from 1 to 65535 seconds. The default value is 40 seconds or the value set for the OSPF dead interval for the interface, whichever is greater.
Command Default
The default value is 40 seconds or the value set for the interface’s OSPF dead interval, whichever is greater.
Command Modes
Interface configuration
Command History
Release
Modification
12.2(15)T
This command was introduced.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(31)SB2
This command was integrated into Cisco IOS Release 12.2(31)SB2.
12.2(33)SXH
This command was integrated into Cisco IOS Release 12.2(33)SXH.
Cisco IOS XE Release 3.2S
This command was modified. Support was added for this command in virtual network interface configuration mode.
Usage Guidelines
When an OSPF nonstop forwarding (NSF) router performs a route processor (RP) switchover, it notifies its neighbors, via a special hello packet, of such action and requests that each neighbor help resynchronize the Link State Database.
When a neighbor (that is NSF-aware) receives the special hello packet from the NSF-capable router, it starts a resync timeout timer and waits to synchronize its database with the NSF-capable router. If the NSF-capable router does not initiate the database resynchronization process before the resync-timeout timer expires, the NSF-aware neighbor will take down the adjacency with the NSF-capable router.
By default, the resync-timeout timer is set to 40 seconds or the dead interval of the interface, whichever is greater. (By default, the dead interval is 4 times the hello interval; the hello interval defaults to 10 seconds for Ethernet or 30 seconds for nonbroadcast.) The ipospfresync-timeout command allows the resync-timeout to be changed and independent of the dead interval or default value.
Examples
This example sets the OSPF resync-timeout interval to 50 seconds:
interface GigabitEthernet 6/0/0
ip ospf resync-timeout 50
Related Commands
Command
Description
ipospfdead-interval
Sets the interval at which hello packets must not be seen before neighbors declare the router down.
ipospfhello-interval
Sets the interval between hello packets that the software sends on the interface.
ip ospf retransmit-interval
To specify the time between link-state advertisement (LSA) retransmissions for adjacencies belonging to the interface, use the
ipospfretransmit-interval command in interface configuration mode. To return to the default value, use the
noform of this command.
ipospfretransmit-intervalseconds
noipospfretransmit-interval
Syntax Description
seconds
Time (in seconds) between retransmissions. The range is from 1 to 65535 seconds. The default is 5 seconds.
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 3.2S
This command was modified. Support was added for this command in virtual network interface configuration mode.
Usage Guidelines
When a router sends an LSA to its neighbor, it keeps the LSA until it receives back the acknowledgment message. If the router receives no acknowledgment, it will resend the LSA.
The setting of the
seconds argument should be greater than the expected round-trip delay between any two routers on the attached network. The setting of this parameter should also be conservative, or needless LSA retransmissions may occur. The value should be larger for serial lines and virtual links.
Note
It is recommended to use the same value for the
seconds argument on neighbor OSPF routers. Using inconsistent values on neighbor routers can cause needless LSA retransmissions.
Examples
The following example sets the retransmit interval value to 8 seconds:
interface ethernet 2
ip ospf retransmit-interval 8
ip ospf shutdown
To initiate an graceful shutdown of Open Shortest Path First (OSPF) protocol at the interface level, use the
ipospfshutdown command in interface configuration mode. To restart the OSPF protocol on an interface, use the
no form of this command.
ipospfshutdown [disable]
noipospfshutdown
Syntax Description
disable
(Optional) Disables the initiation of the OSPF graceful shutdown at the interface level; OSPF stays active at the interface level.
Note
This keyword is available only in virtual network interface mode.
Command Default
OSPF stays active at the interface level.
Command Modes
Interface configuration (config-if)
Virtual network interface (config-if-vnet)
Command History
Release
Modification
12.2(33)SRC
This command was introduced.
15.0(1)M
This command was integrated into Cisco IOS Release 15.0(1)M.
Cisco IOS XE Release 3.2S
This command was modified. The
disable keyword was added. Support was added for this command in virtual network interface configuration mode.
15.0(1)SY
This command was modified. The
disable keyword was added. Support was added for this command in virtual network interface configuration mode.
15.1(1)SG
This command was integrated into Cisco IOS Release 15.1(1)SG.
Cisco IOS XE Release 3.3SG
This command was integrated into Cisco IOS XE Release 3.3SG.
15.3(2)T
This command was integrated into Cisco IOS Release 15.3(2)T.
Usage Guidelines
Use the
ipospfshutdown command to put OSPF in shutdown mode under a specific interface.
If theipospfshutdown command is enabled for a virtual network and you want to disable it, use the
disable keyword in virtual network interface configuration mode.
Examples
The following example shows how to initiate a graceful shutdown of the OSPF protocol on Ethernet interface 0/2:
Router(config)# interface ethernet 0/2
Router(config-if)# ip ospf shutdown
Related Commands
Command
Description
shutdown(routerOSPF)
Initiates a graceful shutdown of the OSPF protocol under the current instance.
ip ospf transmit-delay
To set the estimated time required to send a link-state update packet on the interface, use the
ipospftransmit-delay command in interface configuration mode. To return to the default value, use the
noform of this command.
ipospftransmit-delayseconds
noipospftransmit-delay
Syntax Description
seconds
Time (in seconds) required to send a link-state update. The range is from 1 to 65535 seconds. The default is 1 second.
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 3.2S
This command was modified. Support was added for this command in virtual network interface configuration mode.
Usage Guidelines
Link-state advertisements (LSAs) in the update packet must have their ages incremented by the amount specified in the
seconds argument before transmission. The value assigned should take into account the transmission and propagation delays for the interface.
If the delay is not added before transmission over a link, the time in which the LSA propagates over the link is not considered. This setting has more significance on very low-speed links.
Examples
The following example sets the retransmit delay value to 3 seconds:
interface ethernet 0
ip ospf transmit-delay 3
ip ospf ttl-security
To configure the Time-to-Live (TTL) security check feature on a specific interface, use theipospfttl-securitycommand in interface configuration mode. To disable TTL security on an interface, use the
noform of this command.
ipospfttl-security
[ hopshop-count | disable ]
noipospfttl-security
Syntax Description
hopshop-count
(Optional) Configures the maximum number of IP hops. The
hop-countargument range is from 1 to 254.
disable
(Optional) Disables TTL security on an interface.
Command Default
TTL security is disabled on all Open Shortest Path First (OSPF) interfaces.
This command was integrated into Cisco IOS Release 15.0(1)M.
Cisco IOS XE Release 3.2S
This command was modified. Support was added for this command in virtual network interface configuration mode.
Usage Guidelines
Use the
ipospfttl-security command to configure TTL security on a specific interface.
The
disable keyword can be used to disable TTL security on a specific interface but is only useful if the
ttl-securityall-interfaces command was used in router mode to first configure TTL security on all OSPF interfaces. In this way, all OSPF interfaces can be configured with TTL security and then individual interfaces can be disabled. This can save time as opposed to configuring each interface one-by-one from the start.
Examples
The following example shows how to effectively use the
disable keyword to disable TTL security on Ethernet interface 0/0 after the feature has first been configured on all OSPF interfaces:
Configures TTL security check on all OSPF interfaces.
limit retransmissions
To modify the number of retransmissions of database exchange and update packets for both demand and non-demand circuits, use the
limitretransmissions command in router configuration mode. To reset the maximum number of retransmissions back to the default value of 24, use the
no form of this command.
Maximum number of retransmissions. Range from 1 to 255.
non-dc
Nondemand circuit retransmissions.
disable
Disables or removes the limit to the number of retransmissions.
Command Default
Maximum number of retransmissions is 24.
Command Modes
Router configuration (config-router)#
Address family configuration (config-router-af)#
Command History
Release
Modification
12.2(11)T
This command was introduced.
Cisco IOS XE 3.7S
This command was modified. This command was implemented on the Cisco ASR 1006 Series Device. This command is now supported in address-family configuration mode.
Cisco IOS Release 15.2(1)E
This command was integrated into Cisco IOS Release 15.2(1)E.
Usage Guidelines
There is a limit to the number of retransmissions of database exchange and update packets for both demand and nondemand circuits. The retransmission of these packets stops once this retry limit is reached, thus preventing unnecessary use of the link in continual retransmission of the packets if, for some reason, a neighbor is not responding during adjacency forming.
The limit for both demand circuit and nondemand circuit retransmissions is 24.
The limit-retransmissions command allows you to either remove (disable) the limit or change the maximum number of retransmissions to be a number from 1 to 255. The configuration of this command provides for backward compatibility for previous or other releases of Cisco IOS Software or other routers that do not have this feature.
The limit to the number of retransmissions does not apply for update packets on nonbroadcast multiaccess (NBMA) point-to-multipoint direct circuits. In this situation, the dead timer is used to end communication with nonresponding neighbors and thus stop the retransmissions.
Note
This command can be used in the router configuration mode and address-family mode. The command is also applicable for both OSPF and OSPFv3 protocols.
Examples
The following example shows how to set the maximum number of demand circuit retransmissions to 10 in the router configuration mode:
The following example shows how to set the maximum number of demand circuit retransmissions to 10 and to set the maximum number of nondemand circuit retransmissions to 20:
The following example shows how to set the maximum number of demand circuit retransmissions to 10, and to remove the limit for the number of nondemand circuit retransmissions:
Enters IPv4 or IPv6 address family configuration mode for OSPFv3.
local-rib-criteria
To specify that the OSPF local Routing Information Base (RIB) will be used for route validation, use the local-rib-criteria command in router configuration mode. To remove local RIB route validation, use the noform of this command.
(Optional) Specifies that the local RIB is to be used only for route validation criteria for external or NSSA forwarding addresses.
inter-area-summary
(Optional) Specifies that the local RIB is to be used only for route validation criteria for inter-area summaries.
nssa-translation
(Optional) Specifies that the local RIB is to be used only for route validation criteria for NSSA translation.
Command Default
The global RIB (not the local RIB) is used for route validation.
Command Modes
Router configuration (config-router)
Command History
Release
Modification
12.4(15)T
This command was introduced.
12.2(33)SRC
This command was integrated into Cisco IOS Release 12.2(33)SRC.
12.2(33)SB
This command was integrated into Cisco IOS Release 12.2(33)SB.
Usage Guidelines
If the local-rib-criteria is command is entered without any optional keywords, the local RIB will be used as criteria for all of the options (forwarding address, inter-area summary, and NSSA translation).
You can enter the local-rib-criteria command with one or more of the optional keywords to configure the OSPF routing process to use the local RIB only for forwarding address, inter-area-summary, or NSSA translation route generation.
Note
It is recommended to keep the default behavior (the global RIB is used for route validation). Although entering the local-rib-criteria command alone or with one or more of the optional keywords may result in slightly faster network convergence in some cases, you may potentially cause a problem such as a routing loop or black hole.
Note
When the forwarding-address keyword is entered to specify that forwarding-address verification is modified to use the local RIB, packet forwarding will still be dependent on the global RIB. If the global RIB contains a more preferred or more specific route from a different protocol, this preferred route still will still be used for packet forwarding.
Examples
The following example specifies that the local RIB should be used as the criteria for NSSA translation:
Displays information for the OSPF local RIB or locally redistributed routes.
log-adjacency-changes
To configure the router to send a syslog message when an Open Shortest Path First (OSPF) neighbor goes up or down, use the
log-adjacency-changes command in router configuration mode. To turn off this function, use the
no form of this command.
log-adjacency-changes [detail]
nolog-adjacency-changes [detail]
Syntax Description
detail
(Optional) Sends a syslog message for each state change, not just when a neighbor goes up or down.
Command Default
Enabled
Command Modes
Router configuration (config-router)
Command History
Release
Modification
11.2
This command was introduced as
ospflog-adjacency-changes.
12.1
The
ospf keyword was omitted and the
detail keyword was added.
12.2(15)T
Support for IPv6 was added.
12.2(28)SB
This command was integrated into Cisco IOS Release 12.2(28)SB.
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.
15.1(2)S
This command was integrated into Cisco IOS Release 15.1(2)S.
Usage Guidelines
This command allows you to know about OSPF neighbors going up or down without turning on the
debugipospfpacketcommand or the
debugipv6ospfadjacency command. The
log-adjacency-changes command provides a higher level view of those changes of the peer relationship with less output than the
debug command provides. The
log-adjacency-changes command is on by default but only up/down (full/down) events are reported, unless the
detail keyword is also used.
Examples
The following example configures the router to send a syslog message when an OSPF neighbor state changes:
log-adjacency-changes detail
Related Commands
Command
Description
debugipospfpacket
Displays information about each OSPF packet received for IPv4.
debugipv6ospf
Displays debugging information for OSPF for IPv6.
max-lsa
To limit the number of nonself-generated link-state advertisements (LSAs) that an Open Shortest Path First (OSPF) routing process can keep in the OSPF link-state database (LSDB), use themax-lsa command in router configuration mode. To remove the limit of non self-generated LSAs that an OSPF routing process can keep in the OSPF LSDB, use the no form of this command.
Maximum number of nonself-generated LSAs the OSPF process can keep in the OSPF LSBD.
threshold-percentage
(Optional) The percentage of the maximum LSA number, as specified by the maximum-number argument, at which a warning message is logged. The default is 75 percent.
warning-only
(Optional) Specifies that only a warning message is sent when the maximum limit for LSAs is exceeded. Disabled by default.
ignore-timeminutes
(Optional) Specifies the time, in minutes, to ignore all neighbors after the maximum limit of LSAs has been exceeded. The default is 5 minutes.
ignore-countcount-number
(Optional) Specifies the number of times the OSPF process can consecutively be placed into the ignore state. The default is 5 times.
reset-timeminutes
(Optional) Specifies the time, in minutes, after which the ignore count is reset to zero. The default is 10 minutes.
Command Default
The number of nonself-generated LSAs that an OSPF routing process can keep in the OSPF LSDB is not limited.
This command was integrated into Cisco IOS Release 12.3(7)T.
12.2(25)S
This command was integrated into Cisco IOS Release 12.2(25)S.
12.2(18)SXE
This command was integrated into Cisco IOS Release 12.2(18)SXE.
12.2(27)SBC
This command was integrated into Cisco IOS Release 12.2(27)SBC.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
Usage Guidelines
To prevent the OSPF process from endlessly changing from the normal state of operation to the ignore state as a result of the LSA count exceeding the maximum configured number immediately after it returns from the ignore state to the normal state of operation, the OSPF process keeps a counter on how many times the process went into the ignore state. This counter is called the ignore count. If the ignore count exceeds the maximum number of LSAs that is specified by the ignore-count keyword and counter-number argument, the OSPF process remains in the ignore state permanently. To return the OSPF process to the state of normal operation, enter the clearipospf command.
If the router is placed into a permanent ignore state, we recommend that you identify and correct the cause of the problem involving the router that is generating the LSAs, or, if possible, increase the limit that has been configured by the max-lsa command before you try to bring the router back into normal operation.
If the router that has generated large numbers of LSAs is not reachable, these LSAs cannot be removed from the OSPF area and domain. As a result, any other router leaving the ignore state and returning to normal operation may reach the ignore state again. We recommend that you take one of the following actions in order to bring the router back into the network:
Temporarily increase the LSA limit to account for the stale LSAs.
Wait until the stale LSAs are removed as a result of reaching their maximum age.
Make sure that the router that has generated the large number of LSAs is connected to the network and is no longer generating large numbers of LSAs.
When the warning-only keyword is used, the OSPF process never enters the ignore state. When the LSA count exceeds the maximum limit that is specified by the maximum-number argument, only an error message is logged and the OSPF process continues in its normal operation.
When the max-lsa command is entered for the first time or when any of the parameters of the command are changed, the OSPF process undergoes a soft-reset procedure.
Examples
The following example sets a limit of 12,000 LSAs that can be received before the OSPF process enters the ignore state:
In the following example, an OSPF process has remained in the ignore state permanently. When the clearipospf command is entered the OSPF process returns to the state of normal operation and clears redistribution based on the OSPF routing process ID.
Router(config-router)# clear ip ospf 100 process
Related Commands
Command
Description
clearipospf
Clears redistribution based on the OSPF routing process ID.
max-metric router-lsa
To configure a
router that is running the Open Shortest Path First (OSPF) protocol to
advertise a maximum metric so that other routers do not prefer the router as an
intermediate hop in their shortest path first (SPF) calculations, use the
max-metricrouter-lsacommand in router address family
topology or router configuration mode. To disable the advertisement of a
maximum metric, use the
no form of this
command.
(Optional) Configures the router to override the external LSA metric with the
maximum metric value.
max-metric-value
(Optional) Maximum metric value for LSAs. The configurable range is from 1 to
16777215. The default value is 16711680.
include-stub
(Optional) Configures the router to advertise the maximum metric for stub links
in router LSAs.
on-startup
(Optional) Configures the router to advertise a maximum metric at startup.
seconds
(Optional) Maximum metric value for the specified time interval. The
configurable range is from 5 to 86400 seconds. There is no default timer value
for this configuration option.
wait-for-bgp
(Optional) Configures the router to advertise a maximum metric until Border
Gateway Protocol (BGP) routing tables have converged or the default timer has
expired. The default timer is 600 seconds.
summary-lsa
(Optional) Configures the router to override the summary LSA metric with the
maximum metric value.
Command Default
Router link-state
advertisements (LSAs) are originated with normal link metrics.
Command Modes
Router address
family topology configuration (config-router-af-topology) Router configuration
(config-router)
Command History
Release
Modification
12.0(15)S
This
command was introduced.
12.0(16)ST
This
command was integrated into Cisco IOS Release 12.0(16)ST.
12.2(4)T
This
command was integrated into Cisco IOS Release 12.2(4)T.
12.4(10)
The
include-stub,
summary-lsa,and
external-lsa
keywords and the
max-metric-value argument were made available
under router configuration mode.
12.4(11)T
The
include-stub,
summary-lsa,and
external-lsa
keywords and the
max-metric-value argument were made available
under router configuration mode.
12.2(14)S
This
command was integrated into Cisco IOS Release 12.2(14)S.
12.2(31)SB2
The
include-stub,
summary-lsa,and
external-lsa
keywords and the
max-metric-value argument were made available
under router configuration mode.
12.2(33)SRA
This
command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(33)SRB
This
command was made available in router address family topology configuration
mode. The
include-stub,
summary-lsa,and
external-lsa
keywords and the
max-metric-value argument were made available
under router configuration mode.
15.2(1)E
This command was integrated into Cisco IOS Release 15.2(1)E.
Usage Guidelines
Enabling the
max-metric router-lsa command will cause a router to originate LSAs with a
maximum metric (LSInfinity: 0xFFFF) through all nonstub links, which allows BGP
routing tables to converge without attracting transit traffic (if there are not
alternate lower cost paths around the router). The router will advertise
accurate (normal) metrics after the configured or default timers expire or
after BGP sends a notification that routing tables have converged.
Note
Directly
connected links in a stub network are not affected by the configuration of a
maximum or infinite metric because the cost of a stub link is always set to the
output interface cost.
The max-metric
router-lsa command is useful in the following situations:
Reloading a
router. After a router is reloaded, Interior Gateway Protocols (IGPs) converge
very quickly, and other routers may try to forward traffic through the newly
reloaded router. If the router is still building BGP routing tables, packets
destined for other networks that the router has not learned through BGP may be
dropped. In the case of an Internet backbone router, a large number of packets
may be dropped.
Introducing a
router into a network without routing traffic through it. You may want to
connect a router to an OSPF network but not want real traffic flowing through
the router if there are better alternate paths. If there are no alternate
paths, this router would still accept transit traffic as before.
Gracefully
removing a router from a network. This feature allows you to gracefully remove
a router from the network by advertising a maximum metric through all links,
which allows other routers to select alternate paths for transit traffic to
follow before the router is shut down.
Note
You should not
save the running configuration of a router when it is configured for a graceful
shutdown because the router will continue to advertise a maximum metric after
it is reloaded.
Note
In older OSPF
implementations (RFC 1247 and earlier implementations), the router link costs
in received LSAs with a metric of LSInfinity are not used during SPF
calculations, which means that no transit traffic will be sent to the routers
that originate these LSAs.
Release
12.2(33)SRB
If you plan to
configure the Multi-Topology Routing (MTR) feature, you need to enter the
max-metricrouter-lsacommand in router address family
topology configuration mode in order for this OSPF router configuration command
to become topology-aware.
Examples
The following
example configures a router that is running OSPF to advertise a maximum metric
for 100 seconds:
The following
example configures a router to advertise a maximum metric until BGP routing
tables converge or until the default timer expires (600 seconds):
The following
example configures a router that is running OSPF to advertise a maximum metric,
which causes neighbor routers to select alternate paths for transit traffic
before the router shuts down:
Router(config)# router ospf 100
Router(config-router)# max-metric router-lsa
Router(config-router)# end
The following
example configures stub links to be advertised with the maximum-metric in
routers LSAs.
Entering the
showipospfmax-metriccommand with the
include-stub
keyword displays output that confirms that stub links are advertised with the
maximum metric.
Router# show ip ospf max-metric
Routing Process “ospf 1” with ID 10.1.1.1
Start time: 00:00:03.524, Time elapsed: 01:02:28.292
Originating router-LSAs with maximum metric
Condition: always, State: active
Advertise stub links with maximum metric in router-LSAs
Related Commands
Command
Description
showipospf
Displays general information about OSPF routing processes.
showipospfdatabase
Displays lists of information related to the OSPF database for a specific
router.
neighbor (OSPF)
To configure Open Shortest Path First (OSPF) routers interconnecting to nonbroadcast networks, use the
neighbor command in router address family topology or router configuration mode. To remove a configuration, use the
no form of this command.
(Optional) A number that indicates the router priority value of the nonbroadcast neighbor associated with the IP address specified.The default is 0. This keyword does not apply to point-to-multipoint interfaces.
poll-intervalseconds
(Optional) A number value that represents the poll interval time (in seconds). RFC 1247 recommends that this value be much larger than the hello interval. The default is 120 seconds (2 minutes). This keyword does not apply to point-to-multipoint interfaces. The range is from 0 to 4294967295 seconds.
costnumber
(Optional) Assigns a cost to the neighbor, in the form of an integer from 1 to 65535. Neighbors with no specific cost configured will assume the cost of the interface, based on the
ipospfcostcommand. For point-to-multipoint interfaces, the cost keyword and the number argument are the only options that are applicable. This keyword does not apply to nonbroadcast multiaccess (NBMA) networks.
database-filterall
(Optional) Filters outgoing link-state advertisements (LSAs) to an OSPF neighbor.
Command Default
This command is disabled by default. No configuration is specified.
Command Modes
Router address family topology configuration (config-router-af-topology) Router configuration (config-router)
Command History
Release
Modification
10.0
This command was introduced.
11.3AA
The
cost keyword was added.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(33)SRB
This command was made available in router address family topology configuration mode.
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.
15.1(2)SNG
This command was implemented on the Cisco ASR 901 Series Aggregation Services Routers.
Usage Guidelines
X.25 and Frame Relay provide an optional broadcast capability that can be configured in the map to allow OSPF to run as a broadcast network. At the OSPF level you can configure the router as a broadcast network. Refer to thex25map and
frame-relaymap commands in the “X.25 Commands” and “Frame Relay Commands” chapters, respectively, in the
Cisco IOSWide-AreaNetworkingCommandReferencefor more detail.
One neighbor entry must be included in the Cisco IOS software configuration for each known nonbroadcast network neighbor. The neighbor address must be on the primary address of the interface.
If a neighboring router has become inactive (hello packets have not been received for the Router Dead Interval period), it may still be necessary to send hello packets to the dead neighbor. These hello packets will be sent at a reduced rate called
PollInterval.
When the router first starts up, it sends only hello packets to those routers with nonzero priority, that is, routers that are eligible to become designated routers (DRs) and backup designated routers (BDRs). After the DR and BDR are selected, DR and BDR will then start sending hello packets to all neighbors in order to form adjacencies.
Note
You cannot use the
neighbor(OSPF) command to specify an Open Shortest Path First (OSPF) neighbor on non-broadcast networks within an OSPF Virtual Private Network (VPN) routing instance.
Prior to Cisco IOS Release 12.0, the
neighbor command applied to NBMA networks only. With Release 12.0, the
neighbor command applies to NBMA networks and point-to-multipoint networks. On NBMA networks, the
cost keyword is not accepted.
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the
neighborcommand in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example declares a router at address 192.168.3.4 on a nonbroadcast network, with a priority of 1 and a poll interval of 180 seconds:
The following example illustrates a point-to-multipoint network with nonbroadcast:
interface Serial0
ip address 10.0.1.1 255.255.255.0
ip ospf network point-to-multipoint non-broadcast
encapsulation frame-relay
no keepalive
frame-relay local-dlci 200
frame-relay map ip 10.0.1.3 202
frame-relay map ip 10.0.1.4 203
frame-relay map ip 10.0.1.5 204
no shut
!
router ospf 1
network 10.0.1.0 0.0.0.255 area 0
neighbor 10.0.1.3 cost 5
neighbor 10.0.1.4 cost 10
neighbor 10.0.1.5 cost 15
Related Commands
Command
Description
ipospfpriority
Sets the router priority, which helps determine the designated router for this network.
neighbor database-filter all out
To filter outgoing link-state advertisements (LSAs) to an Open Shortest Path First (OSPF) neighbor, use the
neighbordatabase-filteralloutcommand in router configuration mode. To restore the forwarding of LSAs to the neighbor, use the
noform of this command.
IP address of the neighbor to which outgoing LSAs are blocked.
costmetric
(Optional) Cost metric configured for the specified neighbor. The range of this value is from 0 to 65535.
Command Default
This command is disabled by default. All outgoing LSAs are flooded to the neighbor.
Command Modes
Router configuration
Command History
Release
Modification
12.0
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
This command performs the same function that the
ipospfdatabase-filteralloutcommand performs on an interface basis.
Examples
The following example prevents flooding of OSPF LSAs to point-to-multipoint networks to the neighbor at IP address 10.2.3.4:
router ospf 109
neighbor 10.2.3.4 database-filter all out
Related Commands
Command
Description
ipospfdatabase-filterallout
Filters outgoing LSAs to an OSPF interface.
network area
To define the interfaces on which Open Shortest Path First (OSPF) runs and to define the area ID for those interfaces, use the
networkarea command in router configuration mode. To disable OSPF routing for interfaces defined with the
ip-addresswildcard-maskpair, use the
no form of this command.
networkip-addresswildcard-maskareaarea-id
nonetworkip-addresswildcard-maskareaarea-id
Syntax Description
ip-address
IP address.
wildcard-mask
IP-address-type mask that includes “don’t care” bits.
area-id
Area that is to be associated with the OSPF address range. It can be specified as either a decimal value or as an IP address. If you intend to associate areas with IP subnets, you can specify a subnet address as the value of the
area-idargument.
Command Default
This command is disabled by default.
Command Modes
Router configuration
Command History
Release
Modification
10.0
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.
15.2(2)SNI
This command was implemented on the Cisco ASR 901 Series Aggregation Services Routers.
Usage Guidelines
The ip-address and wildcard-mask arguments together allow you to define one or multiple interfaces to be associated with a specific OSPF area using a single command. Using the
wildcard-mask argument allows you to define one or multiple interfaces to be associated with a specific OSPF area using a single command. If you intend to associate areas with IP subnets, you can specify a subnet address as the value of the
area-idargument.
For OSPF to operate on the interface, the primary address of the interface must be covered by the
networkareacommand. If the
networkareacommand covers only the secondary address, it will not enable OSPF over that interface.
The Cisco IOS software sequentially evaluates the
ip-addresswildcard-mask pair for each interface as follows:
The
wildcard-maskargument is logically ORed with the interface IP address.
The
wildcard-maskargument is logically ORed with the ip-addressargument in the
network command.
The software compares the two resulting values. If they match, OSPF is enabled on the associated interface and this interface is attached to the OSPF area specified.
There is no limit to the number of
networkarea commands you can use on the router.
Note
Any individual interface can only be attached to a single area. If the address ranges specified for different areas overlap, the software will adopt the first area in the
network command list and ignore the subsequent overlapping portions. In general, we recommend that you configure address ranges that do not overlap in order to avoid inadvertent conflicts.
When a more specific OSPF network range is removed, interfaces belonging to that network range will be retained and remain active if and only if a less specific network range exists.
For example, consider the following configuration:
router ospf 1
network 192.168.129.16 0.0.0.3 area 20
network 192.168.129.40 0.0.0.3 area 20
network 192.168.129.44 0.0.0.3 area 20
network 192.168.129.96 0.0.0.3 area 20
network 192.168.128.0 0.0.127.255 area 20
!
Enter the following:
no network 192.168.129.40 0.0.0.3 area 20
Interfaces falling into the network range 192.168.129.40/0.0.0.3 will still remain active because the superset, 192.168.128.0/0.0.127.255, exists for area 20. A more specific network statement will cause interfaces belonging to that range to be removed from a different area only if a less specific network statement (superset) exists.
Consider a configuration such as the following:
!
router ospf 1
network 192.168.128.0 0.0.127.255 area 20
!
If the following network statement is entered:
network 192.168.129.96 0.0.0.3 area 40
then interfaces belonging to range 192.168.129.96/0.0.0.3, if any, are removed from area 20 and moved to area 40. Network statements with identical ranges but with different area IDs are considered as area changes. For example, the following network statements will cause interfaces belonging to network range 192.168.129.40/0.0.0.3 to move from area 20 to area 40:
network 192.168.129.40 0.0.0.3 area 20
network 192.168.129.40 0.0.0.3 area 40
Examples
The following partial example initializes OSPF routing process 109, and defines four OSPF areas: 10.9.50.0, 2, 3, and 0. Areas 10.9.50.0, 2, and 3 mask specific address ranges, and area 0 enables OSPF for all other networks.
interface ethernet 0
ip address 10.108.20.1 255.255.255.0
router ospf 109
network 10.108.20.0 0.0.0.255 area 10.9.50.0
network 10.108.0.0 0.0.255.255 area 2
network 10.109.10.0 0.0.0.255 area 3
network 0.0.0.0 255.255.255.255 area 0
Related Commands
Command
Description
routerospf
Configures an OSPF routing process.
nsf (OSPF)
Note
Effective with Cisco IOS Release 12.0(32)S, the nsf (OSPF) command has been replaced by the nsfcisco command. See the nsfcisco command for more information.
To configure Cisco nonstop forwarding (NSF) operations for Open Shortest Path First (OSPF), use the nsf command in router configuration mode. To disable Cisco NSF for OSPF, use the no form of this command.
nsf
[ enforceglobal ]
nonsf
[ enforceglobal ]
Syntax Description
enforceglobal
(Optional) Cancels NSF restart when non-NSF-aware neighboring networking devices are detected.
Command Default
This command is disabled by default; therefore, NSF operations for OSPF is not configured.
Command Modes
Router configuration (config-router)
Command History
Release
Modification
12.0(22)S
This command was introduced.
12.2(18)S
This command was integrated into Cisco IOS Release 12.2(18)S.
12.2(20)S
This command was implemented on the Cisco 7304 router.
12.0(32)S
This command was replaced by the nsfcisco command.
Usage Guidelines
The user must configure NSF operation for OSPF only if a router is expected to perform NSF during restart. For users to have full NSF benefits, all OSPF neighbors of the specified router must be NSF-aware.
If neighbors that are not NSF-aware are detected on a network interface, NSF restart is aborted on the interface; however, NSF restart will continue on other interfaces. This functionality applies to the default NSF mode of operation when NSF is configured.
If the user configures the optional enforceglobalkeywords, NSF restart will be canceled for the entire process when neighbors that are not NSF-aware are detected on any network interface during restart. NSF restart will also be canceled for the entire process if a neighbor adjacency reset is detected on any interface or if an OSPF interface goes down. To revert to the default NSF mode, enter the nonsfenforceglobal command.
Examples
The following example enters router configuration mode and cancels the NSF restart for the entire OSPF process if neighbors that are not NSF-aware are detected on any network interface during restart:
Router(config)# router ospf 1
Router(config-router)# nsf cisco enforce global
Related Commands
Command
Description
debugipospfnsf
Displays debugging messages related to OSPF NSF commands.
routerospf
Enables OSPF routing and places the router in router configuration mode.
nsf cisco
To enable Cisco nonstop forwarding (NSF) operations on a router that is running Open Shortest Path First (OSPF), use the nsfcisco command in router configuration mode. To return to the default, use the no form of this command.
nsfcisco
[ enforceglobal | helper [disable] ]
nonsfcisco
[ enforceglobal | helperdisable ]
Syntax Description
enforceglobal
(Optional) Cancels NSF restart on all interfaces when neighboring networking devices that are not NSF-aware are detected on any interface during the restart process.
helper
(Optional) Configures Cisco NSF helper mode.
disable
(Optional) Disables helper mode.
Command Default
Cisco NSF restarting mode is disabled. Cisco NSF helper mode is enabled.
Command Modes
Router configuration (config-router)
Command History
Release
Modification
12.0(32)S
This command was introduced. This command replaces the nsf(OSPF) command.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(31)SB2
This command was integrated into Cisco IOS Release 12.2(31)SB2.
12.2(33)SXH
This command was integrated into Cisco IOS Release 12.2(33)SXH.
Usage Guidelines
For Cisco IOS Release 12.0(32)S and later releases, this command replaces the nsf (OSPF) command.
This command enables Cisco NSF on an OSPF router. When NSF is enabled on a router, the router is NSF-capable and will operate in restarting mode.
If a router is expected to cooperate with a neighbor that is doing an NSF graceful restart only, the neighbor router must be running a Cisco software release that supports NSF but NSF need not be configured on the router. When a router is running a Cisco software release that supports NSF, the router is NSF-aware.
By default, neighboring NSF-aware routers will operate in NSF helper mode during a graceful restart. To disable Cisco NSF helper mode on an NSF-aware router, use this command with the disable keyword. To reenable helper mode after explicitly disabling helper mode on an NSF-aware router, use the nonsfciscohelperdisable command.
If neighbors that are not NSF-aware are detected on a network interface during an NSF graceful restart, restart is aborted on that interface only and graceful restart will continue on other interfaces. To cancel restart for the entire OSPF process when neighbors that are not NSF-aware are detected during restart, configure this command with the enforceglobal keywords.
Note
The NSF graceful restart will also be canceled for the entire process when a neighbor adjacency reset is detected on any interface or when an OSPF interface goes down.
Examples
The following example enables Cisco NSF restarting mode on a router and causes the NSF restart to be canceled for the entire OSPF process if neighbors that are not NSF-aware are detected on any network interface during the restart.
router ospf 24
nsf cisco enforce global
Related Commands
Command
Description
nsfietf
Enables IETF NSF.
nsf cisco helper disable
To disable Cisco nonstop forwarding (NSF) helper mode on a Cisco router that is running Open Shortest Path First (OSPF), use the nsfciscohelperdisablecommand in router configuration mode. To reenable Cisco NSF helper mode, use the no form of this command.
nsfciscohelperdisable
nonsfciscohelperdisable
Syntax Description
This command has no arguments or keywords.
Command Default
This command is enabled by default; therefore, NSF helper mode is disabled on a Cisco router that is running OSPF.
Command Modes
Router configuration (config-router)
Command History
Release
Modification
12.0(32)S
This command was introduced.
12.4(6)T
This command was integrated into Cisco IOS Release 12.4(6)T.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(31)SB2
This command was integrated into Cisco IOS Release 12.2(31)SB2.
12.2(33)SXH
This command was integrated into Cisco IOS Release 12.2(33)SXH.
15.0(1)M
This command was integrated into Cisco IOS Release 15.0(1)M.
Cisco IOS XE Release 2.6
This command was integrated into Cisco IOS XE Release 2.6
Usage Guidelines
When a router in an OSPF process has NSF enabled, the router is said to be NSF-capable and will operate in graceful restart mode--the OSPF router process performs nonstop forwarding recovery due to a Route Processor (RP) switchover. By default, the neighboring routers of the NSF-capable router will be NSF-aware and will operate in NSF helper mode. When the NSF-capable router is performing graceful restart, the helper routers assist in the nonstop forwarding recovery process. If you do not want the router to help the restarting neighbor with nonstop forwarding recovery, enter the nsfciscohelperdisable command.
Examples
The following example disables NSF helper mode for the Cisco router on OSPF process 3:
router ospf 3
nsf cisco helper disable
Related Commands
Command
Description
nsfcisco
Enables Cisco NSF on a Cisco router.
nsfietf
Enables IETF nonstop forwarding operations on a router that is running OSPF.
nsfietfhelperdisable
Disables IETF NSF helper mode on a router.
nsfietfhelperstrict-lsa-checking
Enables strict LSA checking on a router.
nsf ietf
To configure Internet Engineering Task Force (IETF) nonstop forwarding (NSF) operations on a router that is running Open Shortest Path First (OSPF), use the nsfietf command in router configuration mode. To return to the default, use the no form of this command.
(Optional) Specifies length of the graceful restart interval, in seconds. The range is from 1 to 1800. The default is 120.
helper
(Optional) Configures NSF helper mode.
disable
(Optional) Disables helper mode on an NSF-aware router.
strict-lsa-checking
(Optional) Enables strict link-state advertisement (LSA) checking for helper mode.
Command Default
IETF NSF graceful restart mode is disabled. IETF NSF helper mode is enabled.
Command Modes
Router configuration (config-router)
Command History
Release
Modification
12.0(32)S
This command was introduced.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(31)SB2
This command was integrated into Cisco IOS Release 12.2(31)SB2.
12.2(33)SXH
This command was integrated into Cisco IOS Release 12.2(33)SXH.
Usage Guidelines
This command enables IETF NSF on an OSPF router. When NSF is enabled on a Cisco router, the router is NSF-capable and will operate in restarting mode.
If a router is expected to cooperate with a neighbor that is doing an NSF graceful restart only, the neighbor router must be running a Cisco software release that supports NSF but NSF need not be configured on the router. When a router is running a Cisco software release that supports NSF, the router is NSF-aware.
By default, neighboring NSF-aware routers will operate in NSF helper mode during a graceful restart. To disable IETF NSF helper mode on an NSF-aware router, use this command with the disable keyword. To reenable helper mode after explicitly disabling helper mode on an NSF-aware router, use the nonsfietfhelperdisable command.
Strict LSA checking allows a router in IETF NSF helper mode to terminate the graceful restart process if it detects a changed LSA that would cause flooding during the graceful restart process. You can configure strict LSA checking on NSF-aware and NSF-capable routers but it is effective only when the router is in helper mode.
Examples
The following example enables IETF NSF restarting mode on a router and changes the graceful restart interval from default (120 seconds) to 200 seconds:
router ospf 24
nsf ietf restart-interval 200
Related Commands
Command
Description
nsfcisco
Enables Cisco NSF.
nsf ietf helper disable
To disable Internet Engineering Task Force (IETF) nonstop forwarding (NSF) helper mode on a router that is running Open Shortest Path First (OSPF), use the nsfietfhelperdisablecommand in router configuration mode. To reenable IETF NSF helper mode, use the no form of this command.
nsfietfhelperdisable
nonsfietfhelperdisable
Syntax Description
This command has no arguments or keywords.
Command Default
This command is disabled by default; therefore, IETF NSF helper mode is enabled on a router that is running OSPF.
Command Modes
Router configuration (config-router)
Command History
Release
Modification
12.0(32)S
This command was introduced.
12.4(6)T
This command was integrated into Cisco IOS Release 12.4(6)T.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(31)SB2
This command was integrated into Cisco IOS Release 12.2(31)SB2.
12.2(33)SXH
This command was integrated into Cisco IOS Release 12.2(33)SXH.
15.0(1)M
This command was integrated into Cisco IOS Release 15.0(1)M.
Cisco IOS XE Release 2.6
This command was integrated into Cisco IOS XE Release 2.6
Usage Guidelines
When a router in an OSPF process has NSF enabled, the router is said to be NSF-capable and will operate in graceful restart mode--the OSPF router process performs nonstop forwarding recovery due to a Route Processor (RP) switchover. By default, the neighboring routers of the NSF-capable router will be NSF-aware and will operate in NSF helper mode. When the NSF-capable router is performing graceful restart, the helper routers assist in the nonstop forwarding recovery process. If you do not want the router to help the restarting neighbor with nonstop forwarding recovery, enter the nsfietfhelperdisable command.
Examples
The following example disables IETF NSF helper mode on a router on OSPF process 4:
router ospf 4
nsf ietf helper disable
Related Commands
Command
Description
nsfcisco
Enables Cisco NSF on a router.
nsfciscohelperdisable
Disables Cisco NSF helper mode on a router.
nsfietf
Enables IETF nonstop forwarding operations on a router that is running OSPF.
nsfietfhelperstrict-lsa-checking
Enables strict LSA checking on a router.
nsf ietf helper strict-lsa-checking
To enable strict link-state advertisement (LSA) checking on routers in an Open Shortest Path First (OSPF) process, use the nsfietfhelperstrict-lsa-checkingcommand in router configuration mode. To disable strict LSA checking, use the no form of this command.
nsfietfhelperstrict-lsa-checking
nonsfietfhelperstrict-lsa-checking
Syntax Description
This command has no arguments or keywords.
Command Default
This command is disabled by default; therefore, strict LSA checking is not done on routers in an OSPF process.
Command Modes
Router configuration (config-router)
Command History
Release
Modification
12.0(32)S
This command was introduced.
12.4(6)T
This command was integrated into Cisco IOS Release 12.4(6)T.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(31)SB2
This command was integrated into Cisco IOS Release 12.2(31)SB2.
12.2(33)SXH
This command was integrated into Cisco IOS Release 12.2(33)SXH.
15.0(1)M
This command was integrated into Cisco IOS Release 15.0(1)M.
Cisco IOS XE Release 2.6
This command was integrated into Cisco IOS XE Release 2.6
Usage Guidelines
To enable strict LSA checking on both NSF-aware and NSF-capable routers, enter the nsfietfhelperstrict-lsa-checking command. However, strict LSA checking will not become effective until the router becomes a helper router during an IETF graceful restart process. With strict LSA checking enabled, the helper router will terminate the helping process of the restarting router if it detects that there is a change to an LSA that would be flooded to the restarting router or if there is a changed LSA on the retransmission list of the restarting router when the graceful restart process is initiated.
Examples
The following example enables strict LSA checking on a router on OSPF process 12:
Enables IETF nonstop forwarding operations on a router that is running OSPF.
nsfietfhelperdisable
Disables IETF NSF helper mode on a router.
nsr
To enable nonstop
routing (NSR) operations on a router that is running Open Shortest Path First
(OSPF), use the
nsrcommand in
router configuration mode. To disable NSR and return to the default, use the
no form of this
command.
nsr
nonsr
Syntax Description
This command has no
arguments or keywords.
Command Default
NSR is disabled.
Command Modes
Router
configuration (config-router)
Command History
Release
Modification
15.1(2)S
This
command was introduced.
Cisco IOS
XE Release 3.3S
This
command was integrated into Cisco IOS XE Release 3.3S.
15.1(2)SY
This
command was integrated into Cisco IOS Release 15.1(2)SY.
15.2(1)E
This command was integrated into Cisco IOS Release 15.2(1)E.
Usage Guidelines
This command
enables NSR on an OSPF router. With NSR enabled, a router with redundant Route
Processors (RPs) is allowed to maintain its OSPF state and adjacencies across
planned and RP switchovers. It does this by checkpointing state information
from OSPF on the active RP to the standby RP. Later, following a switchover to
the standby RP, OSPF can use this checkpointed information to continue
operation without interruption.
This command is
present only in images for platforms that have a hardware or software
redundancy capability.
Examples
The following
example enables NSR on an OSPF router:
To specify the cryptographic authentication keys for an Open Shortest Path First version 3 (OSPFv3) instance, use the ospfv3authentication command in interface configuration mode. To remove the authentication key chain, use theno form of this command.
no ospfv3
[pid] [ipv4|ipv6] authentication
{key-chain
| null
}
Syntax Description
pid
(Optional) Internal identification. The number used here is the number assigned administratively when enabling the OSPFv3 routing process and can be a value from 1 through 65535.
ipv4
(Optional) IPv4 address family.
ipv6
(Optional) IPv6 address family.
authentication
Enables area authentication.
key-chain
Configures a key chain for cryptographic authentication keys.
chain-name
Name of the authentication key that is valid..
null
(Optional) Enables
Message Digest 5 (MD5) authentication on the area specified by the area-id argument.
Command Default
No authentication key is specified.
Command Modes
Interface configuration (config-if)
Command History
Release
Modification
Cisco IOS XE Release 3.11S
This command was introduced.
Usage Guidelines
Use the ospfv3 authentication command to specify the OSPFv3 authentication key chain on an interface. The null keyword is used to override less specific authentication.
Examples
The following example specifies the cryptographic authentication key chain for an OSPFv3 instance:
Enables authentication trailer for an OSPFv3 area.
authentication mode (OSPF)
Specifies the authentication
mode used in OSPFv3.
ospfv3 multi-area
To configure multiarea adjacency on an interface
that is configured with Open Shortest Path First version 3 (OSPFv3), use
the
ospfv3 multi-area
command in interface configuration mode. To
disable multiarea adjacency, use the
no
form of this command.
ospfv3 multi-areamulti-area-id
noospfv3 multi-areamulti-area-id
Syntax Description
multi-area-id
Identifies the area for which authentication is to be enabled. The identifier can be specified as an IP address or a decimal value. The decimal value range is from 0 to 4294967295.
Command Default
No OSPFv3 multiarea adjacency interface is defined.
Command Modes
Interface configuration (config-if)
Command History
Release
Modification
Cisco IOS XE Release 3.11S
This command was introduced.
Examples
The following example shows how to configure OSPFv3 multiarea adjacency on an interface with an area identifier of 100:
Device# enable
Device(config)# interface serial 2/0
Device(config-if)# ospfv3 multi-area 100
Related Commands
Command
Description
ospfv3 multi-area cost
Specifies the cost of sending a packet on an OSPFv3 multiarea interface.
show ospfv3 multi-area
Displays the interface information related to OSPFv3.
ospfv3 multi-area cost
To specify the cost of sending a packet on an
Open Shortest Path First version 3 (OSPFv3) multiarea interface, use
the
ospfv3 multi-area cost
command in interface configuration mode. To
reset the multiarea path cost to the default value, use
the
no
form of this command.
Identifies the area for which authentication is to be enabled. The identifier can be specified as an IP address or a decimal value. The decimal value range is from 0 to 4294967295.
interface-cost
Specifies the unsigned integer value expressed as the link-state metric. The range is from 1 to 65535.
Command Default
Interface cost of the primary interface is inherited for OSPFv3 multiarea adjacency.
Command Modes
Interface configuration (config-if)
Command History
Release
Modification
Cisco IOS XE Release 3.11S
This command was introduced.
Examples
The following example shows how to set the OSPFv3 multiarea interface cost value to 512:
Enables multiarea adjacency on the OSPFv3 interface.
show ospfv3 multi-area
Displays the interface information related to OSPFv3.
prefix-suppression
To prevent Open Shortest Path First (OSPF) from advertising all IP prefixes except prefixes that are associated with loopbacks, secondary IP addresses, and passive interfaces for a specific OSPF process, use the prefix-suppression command in router configuration mode. To advertise all IP prefixes, use the no form of this command.
prefix-suppression
noprefix-suppression
Syntax Description
This command has no arguments or keywords.
Command Default
All IP prefixes are advertised.
Command Modes
Router configuration (config-router)
Command History
Release
Modification
12.4(15)T
This command was introduced.
Cisco IOS XE Release 2.6
This command was integrated into Cisco IOS XE Release 2.6
Usage Guidelines
You can globally suppress all IP prefixes (except prefixes that are associated with loopbacks, secondary IP addresses, and passive interfaces) for an entire OSPF process by using the prefix-suppression command in router configuration mode. You can also suppress IP prefixes on a per-interface basis by using the ipospfprefix-suppression command in interface configuration mode. When the ipospfprefix-suppression command is configured, it takes precedence over the prefix-suppression router configuration command.
Examples
The following example globally suppresses all IP prefixes except prefixes that are associated with loopbacks, secondary IP addresses, and passive interfaces for OSPF process 4:
router ospf 4
prefix-suppression
Related Commands
Command
Description
ipospfprefix-suppression
Prevents OSPF from advertising all IP prefixes that belong to a specific interface, except for IP prefixes that are associated with secondary IP addresses.
process-min-time percent
Note
Effective with Cisco IOS 15.1(1)T release, the process-min-time
percent command is not available in Cisco IOS 15.1(1)T and later releases.
Improvements in Cisco IOS scheduler have made this command unnecessary.
To specify the minimum percentage of CPU process time OSPF takes
before the CPU should yield to a process with a higher priority, use the
process-min-timepercent command in router configuration mode. To
disable this function, use the
no form of this command.
process-min-timepercentpercentage
noprocess-min-timepercent
Syntax Description
percentage
Percentage of CPU process time to be used before trying to
release the CPU for other processes. The valid value range is from 1 to 100.
The default is 25.
Command Default
The default is 25 percent.
Command Modes
Router configuration (config-router)
Command History
Release
Modification
12.2(18)SXF
This command was introduced on the Supervisor Engine 720
and the Supervisor Engine 320.
12.4(4)T
Support for IPv6 was added.
12.2(33)SRA
This command was integrated into Cisco IOS Release
12.2(33)SRA.
15.1(1)T
This command was removed.
Usage Guidelines
Note
Use this command under the direction of Cisco TAC only.
This command is supported by OSPFv2 and OSPFv3.
Use the
process-min-timepercentcommand to configure the minimum percentage of the process
maximum time. Lowering the minimum percentage of CPU usage that a process can
utilize is useful in some circumstances to ensure equitable division of CPU
resources among different tasks. Once the percentage has been exceeded, CPU
control may be given to a higher priority process.
The process maximum time is set using the
process-max-time command. Use the
process-min-timepercentcommand in conjunction with the
process-max-time command.
Examples
The following example shows how to set the percentage of CPU process
time to be used before releasing the CPU:
The following example shows how to return to the default setting in
IPv4:
Router# configure terminal
Router(config)# router ospf
Router(config-router)# no process-min-time percent
Related Commands
Command
Description
process-max-time
Configures the amount of time after which a process should
voluntarily yield to another process.
redistribute maximum-prefix
To limit the number of prefixes redistributed into Open Shortest Path First (OSPF) or to generate a warning when the number of prefixes redistributed into OSPF reaches a maximum, use the redistributemaximum-prefixcommand in router configuration mode. To remove the values, use the no form of this command.
Integer from 1 to 4294967295 that specifies the maximum number of IP prefixes that can be redistributed into OSPF.
When the warning-onlykeyword is configured, the maximum value specifies the number of prefixes that can be redistributed into OSPF before the system logs a warning message. Redistribution is not limited.
The maximum number of IP prefixes that are allowed to be redistributed into OSPF, or the number of prefixes allowed to be redistributed into OSPF before the system logs a warning message, depends on whether the warning-onlykeyword is present.
There is no default value for the maximum argument.
If the warning-onlykeyword is also configured, this value does not limit redistribution; it is simply the number of redistributed prefixes that, when reached, causes a warning message to be logged.
percentage
(Optional) Integer from 1 to 100 that specifies the threshold value, as a percentage, at which a warning message should be generated.
The percentage default is 75.
warning-only
(Optional) Causes a warning message to be logged when the number of prefixes defined by the maximumargumenthas been exceeded. Additional redistribution is not prevented.
withdraw
(Optional) Prevents additional redistribution when the number of prefixes defined by the maximumargumenthas been exceeded.
Also, IS-IS rebuilds link-state PDUs (LSPs) without the external (redistributed) IP prefixes.
Command Default
The percentage default is 75.
Command Modes
Router configuration (config-router)
Command History
Release
Modification
12.0(25)S
This command was introduced.
12.2(18)S
This command was integrated into Cisco IOS Release 12.2(18)S.
12.3(4)T
This command was integrated into Cisco IOS Release 12.3(4)T.
12.2(27)SBC
This command was integrated into Cisco IOS Release 12.2(27)SBC.
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 2.1
This command was introduced on Cisco ASR 1000 Series Aggregation Services Routers.
Usage Guidelines
If someone mistakenly injects a large number of IP prefixes into IS-IS, perhaps by redistributing Border Gateway Protocol (BGP) into IS-IS, the network can be severely flooded. Limiting the number of redistributed prefixes prevents this potential problem.
When the redistributemaximum-prefix command is configured and the number of redistributed prefixes reaches the maximum value configured, no more prefixes will be redistributed (unless the warning-only keyword was configured).
The redistribution limit applies only to external IP prefixes. Default prefixes and summarized prefixes are not limited.
The limit is tracked separately for each not-so-stubby-area (NSSA) because redistribution to NSSAs is done independently for each NSSA and independently of all other regular areas.
Select a maximum value based on your knowledge of how many prefixes are redistributed on the router to the OSPF process.
Examples
Examples
The following example shows how to set a maximum of 600 prefixes that can be redistributed into IS-IS. If the number of prefixes redistributed reaches 75 percent of 600 (450 prefixes), a warning message is logged.
router isis
redistribute maximum-prefix 600
The following example shows how to set a maximum of 1200 prefixes that can be redistributed into IS-IS. If the number of prefixes redistributed reaches 80 percent of 1200 (960 prefixes), a warning message is logged.
router isis
redistribute maximum-prefix 1200 80
The following example shows how to allow two warning messages to be logged. The first message is logged when the number of prefixes redistributed reaches 85 percent of 600 (510 prefixes), and the second message is logged when the number of redistributed prefixes reaches 600. However, the number of redistributed prefixes is not limited.
The following example shows how to set a maximum of 2000 prefixes that can be redistributed into OSPF process when the number of prefixes redistributed reaches 75 percent of 2000 (1500 prefixes), a warning message is logged. Another warning is logged when the limit is reached, and no more prefixes are redistributed.
The following example shows how to set a maximum of 1200 prefixes that can be redistributed into OSPF process when the number of prefixes redistributed reaches 80 percent of 1200 (960 prefixes), a warning message is logged. Another warning is logged when the limit is reached, and no more prefixes are redistributed.
The following example shows how to allow two warning messages to be logged. The first message is logged when the number of prefixes redistributed reaches 85 percent of 600 (510 prefixes), and the second message is logged when the number of redistributed prefixes reaches 600. However, the number of redistributed prefixes is not limited.
To configure an Open Shortest Path First (OSPF) routing process, use the
routerospf command in global configuration mode. To terminate an OSPF routing process, use the
noform of this command.
routerospfprocess-id
[ vrfvrf-name ]
norouterospfprocess-id
[ vrfvrf-name ]
Syntax Description
process-id
Internally used identification parameter for an OSPF routing process. It is locally assigned and can be any positive integer. A unique value is assigned for each OSPF routing process.
vrfvrf-name
(Optional) Specifies the name of the VPN routing and forwarding (VRF) instance to associate with OSPF VRF processes.
Command Default
No OSPF routing process is defined.
Command Modes
Global configuration
Command History
Release
Modification
10.0
This command was introduced.
12.0(7)T
The
vrf keyword and
vpn-name arguments were added to identify a VPN.
12.0(9)ST
The
vrf keyword and
vpn-name arguments were added.
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.
12.2SX
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.
15.1(2)SNG
This command was implemented on the Cisco ASR 901 Series Aggregation Services Routers.
Usage Guidelines
You can specify multiple OSPF routing processes in each router.
After you enter the
routerospf command, you can enter the maximum number of paths. There can be from 1 to 32 paths.
Examples
The following example configures an OSPF routing process and assign a process number of 109:
Router(config)# router ospf 109
This example shows a basic OSPF configuration using the
routerospf command to configure OSPF VRF instance processes for the VRFs first, second, and third:
Router> enable
Router# configure terminal
Router(config)# router ospf 12 vrf first
Router(config)# router ospf 13 vrf second
Router(config)# router ospf 14 vrf third
Router(config)# exit
The following example shows usage of the
maximum-paths option:
Defines the interfaces on which OSPF runs and defines the area ID for those interfaces.
router-id
To use a fixed router ID, use the
router-id command in router configuration mode. To force Open Shortest Path First (OSPF) to use the previous OSPF router ID behavior, use the
no form of this command.
router-idip-address
norouter-idip-address
Syntax Description
ip-address
Router ID in IP address format.
Command Default
No OSPF routing process is defined.
Command Modes
Router configuration
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 configure an arbitrary value in the IP address format for each router. However, each router ID must be unique.
If this command is used on an OSPF router process which is already active (has neighbors), the new router-ID is used at the next reload or at a manual OSPF process restart. To manually restart the OSPF process, use the clear ip ospf command.
Examples
The following example specifies a fixed router-id:
router-id 10.1.1.1
Related Commands
Command
Description
clearipospf
Clears redistribution based on the OSPF routing process ID.