To enter address family configuration mode for Open Shortest Path First (OSPF), use the address-family command in the appropriate mode. To disable address family configuration mode, use the no form of this command.

Command Default

An address family is not specified.

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

OSPF version 2 automatically provides routing services for IPv4 unicast topologies, so this command is redundant.

To configure staggering of OSPF adjacency during reload, process restart, and process clear, use the adjacency stagger command in router configuration mode. To turn off adjacency staggering, either use the disable keyword or use the no form of this command.

Command Default

OSPF adjacency staggering is enabled.

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Staggering of the OSPF adjacency during reload, process restart (without NSR or graceful-restart), and process clear reduces the overall adjacency convergence time.

Initially, allow 2 (configurable) neighbors to form adjacency to FULL per area. After the first adjacency reaches FULL, up to 64 (configurable) neighbors can form adjacency simultaneously for the OSPF instance (all areas). However, areas without any FULL adjacency is restricted by the initial area limit.

Note	Adjacency stagger and OSPF nonstop forwarding (NSF) are mutually exclusive. Adjacency stagger will not be activated if nsf is configured under router ospf configuration.

To configure an Open Shortest Path First (OSPF) area, use the area command in the appropriate mode. To terminate an OSPF area, use the no form of this command.

Command Default

No OSPF area is defined.

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the area command to explicitly configure an area. Commands configured under the area configuration mode (such as the interface [OSPF] and authentication commands), are automatically bound to that area.

To modify or remove the area, the area-id argument format must be the same as the format used when creating the area. Otherwise, even if the actual 32-bit value matches, the area is not matched. For example, if you create an area with an area-id of 10 it would not match an area-id of 0.0.0.10.

Note	To remove the specified area from the router configuration, use the no area area-id command. The no area area-id command removes the area and all area options, such as authentication , default-cost , nssa , range , stub , virtual-link , and interface.

To enable plain text, Message Digest 5 (MD5) authentication, or null authentication for an Open Shortest Path First (OSPF) interface, use the authentication command in the appropriate mode. To remove such authentication, use the no form of this command.

Command Default

If this command is not specified in interface configuration mode, then the interface adopts the authentication parameter specified by the area.

If this command is not specified in area configuration mode, then the interface adopts the authentication parameter specified for the process.

If this command is not specified at any level, then the interface does not use authentication.

If no keyword is specified, plain text authentication is used.

Command Modes

Interface configuration

Area configuration

Router configuration

Virtual-link configuration

Multi-area interface configuration

Sham-link configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the authentication command to specify an authentication type for the interface, which overrides the authentication specified for the area to which this interface belongs. If this command is not included in the configuration file, the authentication configured in the area to which the interface belongs is assumed (as specified by the area authentication command).

The authentication type and password must be the same for all OSPF interfaces that are to communicate with each other through OSPF. If you specified plain text authentication, use the authentication-key command to specify the plain text password.

If you enable MD5 authentication with the message-digest keyword, you must configure a key with the message-digest-key interface command.

To manage the rollover of keys and enhance MD5 authentication for OSPF, you can configure a container of keys called a keychain with each key comprising the following attributes: generate/accept time, key identification, and authentication algorithm. The keychain management feature is always enabled.

Note	Changes to the system clock will impact the validity of the keys in the existing configuration.

Related Commands

To assign a password to be used by neighboring routers that are using the Open Shortest Path First (OSPF) simple password authentication, use the authentication-key command in the appropriate mode. To remove a previously assigned OSPF password, use the no form of this command.

Command Default

If this command is not specified in interface configuration mode, then the interface adopts the OSPF password parameter specified by the area.

If this command is not specified in area configuration mode, then the interface adopts the OSPF password parameter specified for the process.

If this command is not specified at any level, then no password is specified.

Clear is the default if the clear or encrypted keyword is not specified.

Command Modes

Interface configuration

Area configuration

Router configuration

Virtual-link configuration

Multi-area configuration

Sham-link configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

The password created by this command is inserted directly into the OSPF header when the Cisco IOS XR software originates routing protocol packets. A separate password can be assigned to each network on an individual interface basis. All neighboring routers on the same network must have the same password to be able to exchange OSPF information.

The authentication-key command must be used with the authentication command. If the authentication command is not configured, the password provided by the authentication-key command is ignored and no authentication is adopted by the OSPF interface.

Note	The authentication-key command cannot be used with the authentication command when the message-digest or null keyword is configured.

Related Commands

To control how the Open Shortest Path First (OSPF) protocol calculates default metrics for the interface, use the auto-cost command in the appropriate mode. To revert to the default reference bandwidth, use the no form of this command.

Command Default

mbps : 100 Mbps

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

By default OSPF calculates the OSPF metric for an interface according to the bandwidth of the interface.

The OSPF metric is calculated as the mbps value divided by bandwidth, with mbps equal to 108 by default.

If you have multiple links with high bandwidth (such as OC-192), you might want to use a larger number to differentiate the cost on those links. That is, the metric calculated using the default mbps value is the same for all high-bandwidth links.

Recommended usage of cost configuration for OSPF interfaces with high bandwidth is to be consistent: Either explicitly configure (by using the cost command) or choose the default (by using the auto-cost command).

The value set by the cost command overrides the cost resulting from the auto-cost command.

Related Commands

To prevent Multiprotocol Label Switching traffic engineering (MPLS TE) topology information flooded to the network through opaque LSAs, use the capability opaque disable command in the appropriate mode. To restore MPLS TE topology information flooded through opaque LSAs to the network, use the no form of the command.

Command Default

Opaque LSAs are allowed.

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

The capability opaque disable command prevents flooded MPLS TE information (Types 1 and 4) through opaque LSAs of all scope (Types 9, 10, and 11).

Control opaque LSA support capability must be enabled for OSPF to support MPLS TE.

The MPLS TE topology information is flooded to the area through opaque LSAs by default.

To reset an Open Shortest Path First (OSPF) router process without stopping and restarting it, use the clear ospf process command in XR EXEC mode.

Command Default

No default behavior or value

Command Modes

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

When the OSPF router process is reset, OSPF releases all resources allocated, cleans up the internal database, and shuts down and restarts all interfaces that belong to the process.

Note	The clear ospf process command may change the router ID unless the OSPF router ID is explicitly configured through the router-id (OSPF) command.

Related Commands

To clear all routes redistributed from other protocols out of the Open Shortest Path First (OSPF) routing table, use the clear ospf redistribution command in XR EXEC mode.

Command Default

No default behavior or value

Command Modes

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the clear ospf redistribution command to cause the routing table to be read again. OSPF regenerates and sends Type 5 and Type 7 link-state advertisements (LSAs) to its neighbors. If an unexpected route has appeared in the OSPF redistribution, using this command corrects the issue.

Note	Use of this command can cause a significant number of LSAs to flood the network. We recommend that you use this command with caution.

To clear all Open Shortest Path First (OSPF) routes from the OSPF routing table, use the clear ospf routes command in XR EXEC mode.

Command Default

No default behavior or value

Command Modes

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Related Commands

To clear the Open Shortest Path First (OSPF) statistics of neighbor state transitions, use the clear ospf statistics command in XR EXEC mode.

Command Default

No default behavior or value

Command Modes

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the clear ospf statistics command to reset OSPF counters. Reset is useful to detect changes in counter values.

Related Commands

To clear the Open Shortest Path First (OSPF) statistics per interface, use the clear ospf statistics interface command in XR EXEC mode.

Command Default

No default behavior or value.

Command Modes

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the clear ospf statistics interface command to reset OSPF counters. Reset is useful to detect changes in counter values.

Related Commands

To explicitly specify the interface (network) for Open Shortest Path First (OSPF) path calculation, use the cost command in the appropriate mode. To remove the cost, use the no form of this command.

Command Default

If this command is not specified in interface configuration mode, then the interface adopts the cost parameter specified by the area.

If this command is not specified in area configuration mode, then the interface adopts the cost parameter specified for the process.

If this command is not specified at any level, then the cost is calculated by the auto-cost command.

Command Modes

Interface configuration

Area configuration

Router configuration

Multi-area configuration

Sham-link configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

The link-state metric is advertised as the link cost in the router link advertisement. Cisco IOS XR software does not support type of service (ToS), so you can assign only one cost for each interface.

In general, the path cost is calculated using the following formula:

108 / bandwidth (the default auto cost is set to 100 Mbps)

This calculation is the default reference bandwidth used by the auto-costing calculation which establishes the interface auto-cost The auto-cost command can set this reference bandwidth to some other value. The cost command is used to override the auto-costing calculated default value for interfaces.

Using this formula, the default path cost is 1 for any interface that has a link bandwidth of 100 Mbps or higher. If this value does not suit the network, configure the reference bandwidth for auto calculating costs based on the link bandwidth.

The value set by the cost command overrides the cost resulting from the auto-cost (OSPF) command.

Related Commands

To apply higher cost than the normal interface cost when the cumulative bandwidth of a bundle interface goes below the threshold specified and to revert to the original cost if the cumulative bandwidth goes above the configured threshold, use the cost-fallback command. To remove the cost-fallback, use the no form of this command.

Command Default

If this command is not specified in interface configuration mode, the currently effective interface cost takes effect even when the cumulative bandwidth goes down below the maximum bandwidth. Unlike the interface cost command, this cost-fallback command is available only under interface configuration mode; it is not available in area or process level. Unlike other interface specific parameters, no inheritance will take place from area or process level if this command is not specified at interface level.

Command Modes

Interface configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

The fallback cost must be set to a higher value than the normal interface cost. The motivation of setting the fallback cost is to cost out an interface or disfavor an interface without shutting it down when its cumulative bandwidth goes below the user specified threshold, so that the traffic can take an alternative path. The normal interface cost will take over when the cumulative bandwidth reaches or exceeds user-specified threshold.

Related Commands

To filter outgoing link-state advertisements (LSAs) to an Open Shortest Path First (OSPF) interface, use the database-filter all out command in the appropriate mode. To restore the forwarding of LSAs to the interface, use the disable form of the command.

Command Default

The database filter is disabled.

Command Modes

Interface configuration

Area configuration

Router configuration

VRF configuration

Multi-area configuration

Usage Guidelines

No specific guidelines impact the use of this command.

Use the database-file all out command to perform the same function that the neighbor database-filter all out command performs on a neighbor basis.

To set the interval after which a neighbor is declared dead when no hello packets are observed, use the dead-interval command in the appropriate mode. To return to the default time, use the no form of this command.

Command Default

If this command is not specified in interface configuration mode, then the interface adopts the dead interval parameter specified by the area.

If this command is not specified in area configuration mode, then the interface adopts the dead interval parameter specified for the process.

If this command is not specified at any level, then the dead interval is four times the interval set by the hello-interval (OSPF) command.

Command Modes

Interface configuration

Area configuration

Router configuration

Virtual-link configuration

Multi-area configuration

Sham-link configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

The dead interval value must be the same for all routers and access servers on a specific network.

If the hello interval is configured, the dead interval value must be larger than the hello interval value. The dead interval value is usually configured four times larger than the hello interval value.

Related Commands

To specify a cost for the default summary route sent into a stub area or not-so-stubby area (NSSA), use the default-cost command in area configuration mode. To remove the assigned default route cost, use the no form of this command.

Command Default

cost : 1

Command Modes

Area configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the default-cost command only on an Area Border Router (ABR) attached to a stub or an NSSA area.

In all routers and access servers attached to the stub area, the area should be configured as a stub area using the stub command in the area submode. Use the default-cost command only on an ABR attached to the stub area. The default-cost command provides the metric for the summary default route generated by the ABR into the stub area.

Related Commands

To generate a default external route into an Open Shortest Path First (OSPF) routing domain, use the default-information originate command in the appropriate mode. To disable this feature, use the no form of this command.

Command Default

When you do not use this command in router configuration mode, no default external route is generated into an OSPF routing domain.

metric-value : 1

type-value : 2

tag-value: configured OSPF process number

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Whenever you use the redistribute or default-information originate command to redistribute routes into an OSPF routing domain, the software automatically becomes an Autonomous System Boundary Router (ASBR). However, an ASBR does not, by default, generate a default route into the OSPF routing domain. The software still must have a default route for itself before it generates one, except when you have specified the always keyword.

The default-information originate route-policy attach point conditionally injects the default route 0.0.0.0/0 into the OSPF link-state database, and is done by evaluating the attached policy. If any routes specified in the policy exist in the global RIB, then the default route is inserted into the link-state database. If there is no match condition specified in the policy, the policy passes and the default route is generated into the link-state database.

For information about the default-information originate attach point, see the OSPF Policy Attach Points section in the Implementing Routing Policy chapter in Routing Configuration Guide for Cisco NCS 6000 Series Routers.

For information about routing policies, see the Routing Policy Commands chapter in the Routing Command Reference for Cisco NCS 6000 Series Routers.

Related Commands

To set default metric values for routes redistributed from another protocol into the Open Shortest Path First (OSPF) protocol, use the default-metric command in the appropriate mode. To return to the default state, use the no form of this command.

Command Default

Built-in, automatic metric translations, as appropriate for each routing protocol.

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the default-metric command with the redistribute command to cause the current routing protocol to use the same metric value for all redistributed routes. A default metric helps solve the problem of redistributing routes with incompatible metrics. Whenever metrics do not convert, use a default metric to provide a reasonable substitute and enable the redistribution to proceed.

The default-metric value configured in OSPF configuration does not apply to connected routes that are redistributed to OSPF using the redistribute connected command. To set a non-default metric for connected routes, configure OSPF with the redistribute connected metric metric-value command.

Related Commands

To configure the Open Shortest Path First (OSPF) protocol to treat the interface as an OSPF demand circuit, use the demand-circuit command in the appropriate mode. To remove the demand circuit designation from the interface, use the no form of this command.

Command Default

If this command is not specified in interface configuration mode, then the interface adopts the demand circuit parameter specified by the area.

If this command is not specified in area configuration mode, then the interface adopts the demand circuit parameter specified for the process.

If this command is not specified at any level, then the circuit is not a demand circuit.

Command Modes

Interface configuration

Area configuration

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

On point-to-point interfaces, only one end of the demand circuit must be configured with this command. Periodic hello messages are suppressed and periodic refreshes of link-state advertisements (LSAs) do not flood the demand circuit. Use the demand-circuit command to allow the underlying data link layer to be closed when the topology is stable. In point-to-multipoint topology, only the multipoint end must be configured with this command.

To define an administrative distance, use the distance command in an appropriate configuration mode. To remove the distance command from the configuration file and restore the system to its default condition in which the software removes a distance definition, use the no form of this command.

Command Default

If this command is not specified, then the administrative distance is the default, as specified in Table 1.

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

An administrative distance is an integer from 10 to 255. In general, the higher the value, the lower the trust rating. An administrative distance of 255 means that the routing information source cannot be trusted at all and should be ignored. Weight values are subjective; no quantitative method exists for choosing weight values.

If an access list is used with this command, it is applied when a network is being inserted into the routing table. This behavior allows you to filter networks based on the IP prefix supplying the routing information. For example, you could filter possibly incorrect routing information from networking devices not under your administrative control.

The order in which you enter distance commands can affect the assigned administrative distances in unexpected ways (see the “Examples” section for further clarification).

Related Commands

To define Open Shortest Path First (OSPF) route administrative distances based on route type, use the distance ospf command in router configuration mode. To restore the default value, use the no form of this command.

Command Default

distance : 110

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

You must specify one of the keywords.

Use the distance ospf command to perform the same function as the distance command used with an access list. However, the distance ospf command sets a distance for an entire group of routes, rather than a specific route that passes an access list.

A common reason to use the distance ospf command is when you have multiple OSPF processes with mutual redistribution, and you want to prefer internal routes from one over external routes from the other.

To filter networks received or transmitted in Open Shortest Path First (OSPF) updates, use the distribute-list command in the appropriate mode. To change or cancel the filter, use the no form of this command.

Command Default

If this command is not specified in interface configuration mode, then the interface adopts the distribute list parameter specified by the area.

If this command is not specified in area configuration mode, then the interface adopts the distribute list parameter specified for the process.

If this command is not specified at any level, then the distribute list is disabled.

Command Modes

Interface configuration

Area configuration

Router configuration

Multi-area configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the distribute-list command to limit which OSPF routes are installed on this router. The distribute-list command does not affect the OSPF protocol itself.

The distribute-list in is configurable at instance (process), area, and interface levels. Regular OSPF configuration inheritance applies. Configuration is inherited from instance > area > interface levels.

The "if tag..." statements can be used in distribute-list in route-policy. The matching on route tag supports operators "eq/ge/is/le". Operator "in" is not supported.

To enable IP fast reroute loop-free alternate (LFA) computation, use the fast-reroute command in the appropriate OSPF configuration mode. To disable the IP fast reroute loop-free alternate computation, use the no form of this command.

To disable loop-free alternate computation that is enabled on a higher level, use the fast-reroute command with disable keyword.

Command Default

IP fast-reroute LFA computation is disabled.

Command Modes

Area configuration

Interface configuration

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Only one mode of computation can be configured on an interface - per-link or per-prefix. Different modes of computations can be enabled on different interfaces; one set of interface using per-link and other set using per-prefix computation. Based on the outgoing interface of the primary path, per-link or per-prefix backup path will be computed.

To excludes specified interface to be used as a backup during (IPFRR) loop-free alternate (LFA) computation, use the fast-reroute per-link exclude interface command, in the appropriate OSPF configuration mode. To disable this feature, use the no form of this command.

Command Default

No interfaces are excluded.

Command Modes

Interface configuration

Area configuration

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Related Commands

To exclude interface to be used as a backup path from fast-reroute loop-free alternate per-prefix computation, use the fast-reroute per-prefix exclude interface command in the appropriate OSPF configuration mode. To disable this feature, use the no form of this command.

Command Default

No interfaces are excluded.

Command Modes

Interface configuration

Area configuration

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Backup paths via the excluded interfaces will not be computed.

To add interfaces to the LFA candidate list, use the fast-reroute per-prefix lfa-candidate command in interface configuration mode. To disable this feature, use the no form of this command.

Command Default

No interfaces are added to the candidate list.

Command Modes

Interface configuration

Area configuration

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

To configure fast-reroute per-prefix remote loop-free alternate (rLFA) computation for an OSPFv2 process, use the fast-reroute per-prefix remote-lfa command in the appropriate OSPF configuration mode. To disable this feature, use the no form of this command.

Command Default

Remote LFA FRR computation is disabled.

Command Modes

Router configuration

Area configuration

Interface configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Fast-reroute per-prefix LFA must be enabled for remote LFA to be operational. The OSPF configuration hierarchy at process level and area level are applicable for remote LFA configuration. For example, it is possible to enable remote-LFA for all OSPF areas and selectively disable (using disable keyword) the computation under one or more area.

Related Commands

To restrict the backup interfaces to those that are present on the LFA candidate list, use the fast-reroute per-prefix use-candidate-only command in router OSPF configuration mode. To disable this feature, use the no form of this command.

Command Default

Disabled.

Command Modes

Router OSPF configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

To suppress the unnecessary flooding of link-state advertisements (LSAs) in stable topologies, use the flood-reduction command in the appropriate mode. To remove this functionality from the configuration, use the no form of this command.

Command Default

If this command is not specified in interface configuration mode, then the interface adopts the flood reduction parameter specified by the area.

If this command is not specified in area configuration mode, then the interface adopts the flood reduction parameter specified for the process.

If this command is not specified at any level, then flood reduction is disabled.

Command Modes

Interface configuration

Area configuration

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

All routers supporting the OSPF demand circuit are compatible and can interact with routers supporting flooding reduction.

Related Commands

To specify the interval between consecutive hello packets that are sent on the Open Shortest Path First (OSPF) interface, use the hello-interval command in the appropriate mode. To return to the default time, use the no form of this command.

Command Default

If this command is not specified in interface configuration mode, then the interface adopts the hello interval parameter specified by the area.

If this command is not specified in area configuration mode, then the interface adopts the hello interval parameter specified for the process.

If this command is not specified at any level, then the hello interval is 10 seconds (broadcast) or 30 seconds (non-broadcast).

Command Modes

Interface configuration

Area configuration

Router configuration

Virtual-link configuration

Multi-area configuration

Sham-link configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

The hello interval value is advertised in the hello packets. The shorter the hello interval, the faster topological changes are detected, but more routing traffic occurs. This value must be the same for all routers and access servers on a specific network.

Related Commands

To define the interfaces on which the Open Shortest Path First (OSPF) protocol runs, use the interface command in area configuration mode. To disable OSPF routing for interfaces, use the interface form of this command.

Command Default

When you do not specify this command in configuration mode, OSPF routing for interfaces is not enabled.

Command Modes

Area configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the interface command to associate a specific interface with an area. The interface remains associated with the area even when the IP address of the interface changes.

To configure the router to send a syslog message when the state of an Open Shortest Path First (OSPF) neighbor changes, use the log adjacency changes command in router configuration mode. To turn off this function, use the disable keyword. To log all state changes, use the detail keyword.

Command Default

The router sends a syslog message when the state of an OSPF neighbor changes.

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the log adjacency changes command to display high-level changes to the state of the peer relationship. Configure this command if you want to know about OSPF neighbor changes.

To enable advertising loopback as stub networks, use the loopback stub-network command in an appropriate configuration mode. To disable advertising loopback as stubnetworks, use the no form of this command.

Command Default

By default, OSPF advertises loopbacks as stub hosts.

Command Modes

OSPF interface configuration  

OSPF router configuration

OSPF area configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

In the interface submode, the command can be enabled only on loopback interfaces.

Related Commands

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 the max-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.

Command Default

Disabled

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

This command allows you to protect the OSPF routing process from the large number of received LSAs that can result from a misconfiguration on another router in the OSPF domain (for example, the redistribution of a large number of IP prefixes to OSPF).

When this feature is enabled, the router keeps count of the number of all received (nonself-generated) LSAs. When the configured threshold value is reached, an error message is logged. When the configured max number of received LSAs is exceeded, the router stops accepting new LSAs.

If the count of received LSAs is higher than the configured max number after one minute, the OSPF process disables all adjacencies in the given context and clears the OSPF database. This state is called the ignore state. In this state, all OSPF packets received on all interfaces belonging to the OSPF instance are ignored and no OSPF packets are generated on its interfaces. The OSPF process remains in the ignore state for the duration of the configured ignore-time . When the ignore-time expires, the OSPF process returns to normal operation and starts building adjacencies on all its interfaces.

To prevent the OSPF instance from endlessly oscillating between its normal state and the ignore state, as a result of the LSA count immediately exceeding the max number again after it returns from the ignore state, the OSPF instance keeps a count of how many times it has been in the ignore state. This counter is called the ignore-count . If the ignore-count exceeds its configured value, the OSPF instance remains in the ignore state permanently.

To return the OSPF instance to its normal state, you must issue the clear ip ospf command. The ignore-count is reset to zero if the LSA count does not exceed the max number again during the time configured by the reset-time keyword.

If you use the warning-only keyword, the OSPF instance never enters the ignore state. When LSA count exceeds the max number, the OSPF process logs an error message and the OSPF instance continues in its normal state operation.

Related Commands

To configure the Open Shortest Path First (OSPF) protocol to signal other networking devices not to prefer the local router as an intermediate hop in their shortest path first (SPF) calculations, use the max-metric command in router configuration mode. To disable this function, use the no form of this command.

Command Default

Router LSAs are originated with normal link metrics.

overriding-metric :16711680

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the max-metric command to cause the software to originate router LSAs with router link metrics set to LSInfinity (0XFFFF). This feature can be useful in Internet backbone routers that run both OSPF and BGP because OSPF converges more quickly than BGP and may begin attracting traffic before BGP has converged, resulting in dropped traffic.

If this command is configured, the router advertises its locally generated router LSAs with a metric of 0XFFFF. This action allows the router to converge but not attract transit traffic if there are better, alternative paths around this router. After the specified announce-time value or notification from BGP has expired, the router advertises the local router LSAs with the normal metric (interface cost).

If this command is configured with the on-startup keyword, then the maximum metric is temporarily set only after reboot is initiated. If this command is configured without the on-startup keyword, then the maximum metric is permanently used until the configuration is removed.

If the include-stub keyword is enabled, the stub-links in the router LSA will be sent with the max-metric. If the summary-lsa keyword is enabled, all self-generated summary LSAs will have a metric set to 0xFF0000, unless the metric value is specified with the max-metric value parameter. If the external-lsa keyword is enabled, all self-generated external LSAs will have a metric set to 0xFF0000, unless the metric value is specified with the max-metric value parameter.

This command might be useful when you want to connect a router to an OSPF network, but do not want real traffic flowing through it if there are better, alternative paths. If there are no alternative paths, this router still accepts transit traffic as before.

Some cases where this command might be useful are as follows:

• During a router reload, you prefer that OSPF wait for BGP to converge before accepting transit traffic. If there are no alternative paths, the router still accepts transit traffic.
• A router is in critical condition (for example, it has a very high CPU load or does not have enough memory to store all LSAs or build the routing table).
• When you want to gracefully introduce or remove a router to or from the network.
• When you have a test router in a lab, connected to a production network.

Note	For older OSPF implementations (RFC 1247), router links in received router LSAs with a metric and cost of LSInfinity are not used during SPF calculations. Hence, no transit traffic is set to the routers originating such router LSAs.

To limit the number of interfaces that can be configured for an Open Shortest Path First (OSPF) process, use the maximum interfaces command in the appropriate mode. To return to the default limit, use the no form of this command.

Command Default

If the command is not specified, the default is 1024.

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the maximum interface command to increase or decrease the limit on the number of interfaces configured for an OSPF process.

You cannot configure a limit lower than the number of interfaces currently configured for the OSPF process. To lower the limit, remove interfaces from the OSPF configuration until the number of configured interfaces is at or below the desired limit. You may then apply the new, lower limit.

Related Commands

To control the maximum number of parallel routes that the Open Shortest Path First (OSPF) protocol can support, use the maximum paths command in an appropriate configuration mode. To remove the maximum paths command from the configuration file and restore the system to its default condition with respect to the routing protocol, use the no form of this command.

Command Default

32 paths

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

The default value for maximum-path depends on the platform supported maximum-path value. Any custom value you define for the maximum-path parameter must be within the maximum value supported by platform. The configuration will be rejected if the value you have specified is more then what the platform supports.

When the maximum number of parallel routes is reduced, all existing paths are pruned and paths reinstalled at the new maximum number. During this route-reduction period, you may experience some packet loss for a few seconds. This may impact route traffic.

To limit the aggregate number of prefixes that can be redistributed into an Open Shortest Path First (OSPF) process, use the maximum redistributed-prefix command in the appropriate mode. To return to the default limit, use the no form of this command.

Command Default

If the command is not specified, the default is 10000.

The threshold value defaults to 75 percent.

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the maximum redistributed-prefixes command to increase or decrease the maximum number of prefixes (also referred to as routes) redistributed for an OSPF process.

If the maximum value is less than the existing number of routes, existing routes remain configured, but no new routes are redistributed.

Related Commands

To specify a key used with Open Shortest Path First (OSPF) Message Digest 5 (MD5) authentication, use the message-digest-key command in the appropriate mode. To remove an old MD5 key, use the no form of this command.

Command Default

If this command is not specified in interface configuration mode, then the interface adopts the message digest key parameter specified by the area.

If this command is not specified in area configuration mode, then the interface adopts the message digest key parameter specified for the process.

If this command is not specified at any level, then OSPF MD5 authentication is disabled.

Command Modes

Interface configuration

Area configuration

Router configuration

Virtual-link configuration

Multi-area configuration

Sham-link configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Usually, one key individual interface is used to generate authentication information when packets are sent and to authenticate incoming packets. The same key identifier on the neighbor router must have the same key value.

For authentication to be enabled, you must configure the message-digest-key command together with the authentication command and its message-digest keyword. Both the message-digest-key and authentication commands can be inherited from a higher configuration level.

The process of changing keys is as follows. Suppose the current configuration is:

  interface GigabitEthernet 0/3/0/2
   message-digest-key 100 md5 OLD
  
  

You change the configuration to the following:

  interface GigabitEthernet 0/3/0/2
   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 after 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 ospf message-digest-key 100
  

Then, only key 101 is used for authentication on interface 1.

We recommend that you not keep more than one key individual 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	The MD5 key is always stored in encrypted format on the router. The clear and encrypted keywords inform the router whether the value that is entered is encrypted or unencrypted.

Related Commands

To enable Label Distribution Protocol (LDP)-Interior Gateway Protocol (IGP) interface automatic configuration, use the mpls ldp auto-config command in the appropriate mode. To disable LDP-IGP interface automatic configuration, use the no form of this command.

Command Default

LDP-IGP interface automatic configuration is disabled for OSPF.

Command Modes

Interface configuration

Area configuration

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

To enable Label Distribution Protocol (LDP)-Interior Gateway Protocol (IGP) synchronization, use the mpls ldp sync command in the appropriate mode. To disable LDP-IGP synchronization, use the no form of this command.

Command Default

LDP-IGP synchronization is disabled for OSPF.

Command Modes

Interface configuration

Area configuration

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

To configure and enable Label Distribution Protocol- Interior Gateway Protocol (LDP-IGP) synchronization on Multiprotocol Label Switching (MPLS) shortcuts (auto-route announced tunnels) only, use the mpls ldp sync-igp-shortcuts command in the appropriate OSPF configuration mode. To disable the use of LDP-IGP synchronization on MPLS shortcuts, use the no form of this command.

Command Default

LDP-IGP synchronization is disabled on MPLS tunnels.

Command Modes

OSPF interface configuration

OSPF router configuration

OSPF area configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

When mpls ldp sync-igp-shortcuts is configured at a higher mode (area or instance level), you can selectively disable LDP-IGP synchronization on specific interfaces or areas by using the disable form of the command.

Related Commands

To enable Label Distribution Protocol (LDP)-OSPF Type 1 and Type 10 link-state advertisement (LSA) synchronization, use the mpls traffic-eng ldp-sync-update command in the appropriate mode. To disable LDP-LSA synchronization, use the no form of this command.

Command Default

LDP-LSA synchronization is disabled for OSPF.

Command Modes

Router configuration

Interface configuration

Area configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Whenever there is a change in the network (link failure, addition, new nodes, cost change or router cost out), the Type 1 and Type 10 LSA should be in sync. In most of the cases Type 1 and Type 10 are in sync, however it was observed that when IGP-LDP sync is not established, the Type 1 indicates the high cost while the Type 10 shows the normal cost. Use the mpls traffic-eng ldp-sync-update command to synchronize Label Distribution Protocol (LDP)-OSPF Type 1 and Type 10 link-state advertisement (LSA).

To prevent Open Shortest Path First (OSPF) from checking whether neighbors are using the same maximum transmission unit (MTU) on a common interface when exchanging database descriptor (DBD) packets, use the mtu-ignore command in the appropriate mode. To reset to default, use the no form of this command.

Command Default

The default is mtu-ignore with no keywords, which disables MTU checking.

If this command is not specified in interface configuration mode,

then the interface adopts the MTU ignore parameter specified by the area.

If this command is not specified in area configuration mode,

then the interface adopts the MTU ignore parameter specified for the process.

If this command is not specified at any level,

then OSPF checks the MTU received from neighbors when exchanging DBD packets.

Command Modes

Interface configuration

Area configuration

Router configuration

Multi-area configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

OSPF checks whether OSPF 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 MTU configured on the incoming interface, OSPF adjacency is not established.

The keywords, disable and enable , do not need to be used. If no keywords are used, the mtu-ignore command disables MTU checking. You can then use the no mtu-ignore command to activate MTU checking.

To enable multiple adjacencies for different Open Shortest Path First (OSPF) areas and enter multi-area interface configuration mode, use the multi-area-interface command in the area configuration mode. To reset to the default, use the no form of this command.

Command Default

An OSPF network is enabled for one area only.

Command Modes

Area configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the multi-area-interface command to enable area border routers (ABRs) to establish multiple adjacencies for different OSPF areas.

Each multiple area adjacency is announced as a point-to-point unnumbered link in the configured area. This point-to-point link provides a topological path for that area. The first or primary adjacency using the link advertises the link consistent with draft-ietf-ospf-multi-area-adj-06.txt.

You can configure multi-area adjacency on any interface where only two OSF speakers are attached. In the case of native broadcast networks, the interface must be configured as an OPSF point-to-point type using the network point-to-point command to enable the interface for a multi-area adjacency.

Related Commands

To configure Open Shortest Path First (OSPF) routers interconnecting to nonbroadcast networks, use the neighbor command in interface configuration mode. To remove a configuration, use the no form of this command.

Command Default

No configuration is specified.

priority number : 0

poll-interval seconds : 120 seconds (2 minutes)

Command Modes

Interface configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

You must include one neighbor entry in the 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 are sent at a reduced rate called the poll interval.

When the router 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, the DR and BDR start sending hello packets to all neighbors to form adjacencies.

To filter all outgoing OSPF link-state advertisement (LSA) packets for the neighbor, use the neighbor database-filter all out command.

Related Commands

To filter all outgoing link-state advertisements (LSAs) to an Open Shortest Path First (OSPF) neighbor, use the neighbor database-filter all out command in interface configuration mode. To restore the forwarding of LSAs to the neighbor, use the no form of this command.

Command Default

Instead of all outgoing LSAs being filtered to the neighbor, they are flooded to the neighbor.

Command Modes

Interface configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Use the neighbor database-filter all out command to filter all outgoing OSPF LSA packets during synchronization and flooding for point-to-multipoint neighbors on nonbroadcast networks. More neighbor options are available with the neighbor command.

Related Commands

To configure the Open Shortest Path First (OSPF) network type to a type other than the default for a given medium, use the network command in the appropriate mode. To return to the default value, use the no form of this command.

Command Default

If this command is not specified in interface configuration mode, then the interface adopts the network parameter specified by the area.

If this command is not specified in area configuration mode, then the interface adopts the network parameter specified for the process.

If this command is not specified at any level, then the OSPF network type is the default of the given medium.

POS interfaces default to point-to-point and GigabitEthernt and TenGigEthernet interfaces default to broadcast.

Command Modes

Interface configuration

Area configuration

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Configuring NBMA networks as either broadcast or nonbroadcast assumes that there are virtual circuits from every router to every router or fully meshed network. 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 go through the router that has virtual circuits to both routers.

If this command is issued on an interface that does not allow it, this command is 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.

Related Commands

To configure nonstop forwarding (NSF) for the Open Shortest Path First (OSPF) protocol, use the nsf command in the appropriate mode. To remove this command from the configuration file and restore the system to its default condition, use the no form of this command.

Command Default

NSF is disabled.

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

The NSF feature allows for the forwarding of data packets to continue along known routes while routing protocol information (such as OSPF) is being restored following a switchover.

Use the nsf command if the router is expected to perform NSF during restart. To experience the full benefits of this feature, configure all neighboring routers with NSF.

When this command is used without the optional cisco enforce global keywords and non-NSF neighbors are detected, the NSF restart mechanism aborts on the interfaces of those neighbors and functions properly on others.

When this command is used with the optional cisco enforce global keywords and non-NSF neighbors are detected, NSF restart is canceled for the entire OSPF process.

IETF graceful restart provides an NSF mechanism to allow data traffic to flow seamlessly with no packet drops during the transient period when OSPF attempts to recover after a process restart or RP failover, within the guidelines of RFC 3623.

By default, neighbors in helper mode listen to both the NSF Cisco- and NSF IETF-type LSAs. The nsf command enables one type of mechanism that would undergo an RP failover or, anticipating an OSPF process restart. If the cisco or ietf keyword is not entered, NSF is not enabled, irrespective of neighbors in listening mode for both NSF Cisco and NSF IETF.

To configure the maximum time allowed for nonstop forwarding (NSF) external route queries for the Open Shortest Path First (OSPF) protocol, use the nsf flush-delay-time command in the appropriate mode. To remove this command from the configuration file and restore the system to its default condition, use the no form of this command.

Command Default

seconds : 300

Command Modes

Router configuration

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes appropriate task IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

To configure the minimum time between consecutive nonstop forwarding (NSF) restart attempts for the Open Shortest Path First (OSPF) protocol, use the nsf interval command in the appropriate mode. To remove this command from the configuration file and restore the system to its default condition, use the no form of this command.