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Cisco IOS IP Routing Protocols Command Reference
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Introduction
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BGP Commands: A through B
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BGP Commands: C through I
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BGP Commands: M through neighbor soo
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BGP Commands: neighbor timers through show bgp nsap summary
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BGP Commands: show ip bgp through T
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EIGRP Commands: A through I
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EIGRP Commands: M through V
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Integrated IS-IS Commands: A through I
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Integrated IS-IS Commands: L through V
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On-Demand Routing Commands
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OSPF Commands: A through ip ospf demand-circuit
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OSPF Commands: ip ospf flood-reduction through R
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OSPF Commands: show ip ospf through T
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IP Routing Protocol-Independent Commands: A through R
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IP Routing Protocol-Independent Commands: S through T
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RIP Commands
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Table Of Contents
default-information originate (OSPF)
ip ospf database-filter all out
OSPF Commands
area authentication
To enable authentication for an Open Shortest Path First (OSPF) area, use the area authentication command in router configuration mode. To remove an authentication specification of an area or a specified area from the configuration, use the no form of this command.
area area-id authentication [message-digest]
no area area-id authentication [message-digest]
Syntax Description
Defaults
Type 0 authentication (no authentication)
Command Modes
Router configuration
Command History
Usage Guidelines
Specifying authentication for an area sets the authentication to Type 1 (simple password) as specified in RFC 1247. If this command is not included in the configuration file, authentication of Type 0 (no authentication) is assumed.
The authentication type must be the same for all routers and access servers in an area. The authentication password for all OSPF routers on a network must be the same if they are to communicate with each other via OSPF. Use the ip ospf authentication-key interface command to specify this password.
If you enable MD5 authentication with the message-digest keyword, you must configure a password with the ip ospf message-digest-key interface command.
To remove the authentication specification for an area, use the no form of this command with the authentication keyword.
Note
To remove the specified area from the software configuration, use the no area area-id command (with no other keywords). That is, the no area area-id command removes all area options, such as area authentication, area default-cost, area nssa, area range, area stub, and area virtual-link.
Examples
The following example mandates authentication for areas 0 and 10.0.0.0 of OSPF routing process 201. Authentication keys are also provided.
interface ethernet 0ip address 192.168.251.201 255.255.255.0ip ospf authentication-key adcdefgh!interface ethernet 1ip address 10.56.0.201 255.255.0.0ip ospf authentication-key ijklmnop!router ospf 201network 10.0.0.0 0.255.255.255 area 10.0.0.0network 192.168.0.0 0.0.255.255 area 0area 10.0.0.0 authenticationarea 0 authenticationRelated Commands
area default-cost
To specify a cost for the default summary route that is sent into a stub area or not-so-stubby area (NSSA), use the area default-cost command in router address family topology or router configuration mode. To remove the assigned default route cost, use the no form of this command.
area area-id default-cost cost
no area area-id default-cost cost
Syntax Description
Command Default
cost: 1
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
This command is used only on an Area Border Router (ABR) attached to a stub area or NSSA.
There are two stub area router configuration commands: the stub and default-cost options of the area command. In all routers and access servers attached to the stub area, the area should be configured as a stub area using the stub option of the area command. Use the default-cost option only on an ABR attached to the stub area. The default-cost option provides the metric for the summary default route generated by the ABR into the stub area.
Note
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the area default-cost command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example assigns a default cost of 20 to stub network 10.0.0.0:
interface ethernet 0ip address 10.56.0.201 255.255.0.0!router ospf 201network 10.0.0.0 0.255.255.255 area 10.0.0.0area 10.0.0.0 stubarea 10.0.0.0 default-cost 20Related Commands
area authentication
Enables authentication for an OSPF area.
area stub
Defines an area as a stub area.
area filter-list
To filter prefixes advertised in type 3 link-state advertisements (LSAs) between Open Shortest Path First (OSPF) areas of an Area Border Router (ABR), use the area filter-list command in router address family topology or router configuration mode. To change or cancel the filter, use the no form of this command.
area area-id filter-list prefix prefix-list-name {in | out}
no area area-id filter-list prefix prefix-list-name {in | out}
Syntax Description
Command Default
This command is disabled by default. The router will not filter prefixes.
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
With this feature enabled in the "in" direction, all type 3 LSAs originated by the ABR to this area, based on information from all other areas, are filtered by the prefix list. Type 3 LSAs that were originated as a result of the area range command in another area are treated like any other type 3 LSA that was originated individually. Any prefix that does not match an entry in the prefix list is implicitly denied.
With this feature enabled in the "out" direction, all type 3 LSAs advertised by the ABR, based on information from this area to all other areas, are filtered by the prefix list. If the area range command has been configured for this area, type 3 LSAs that correspond to the area range are sent to all other areas, only if at least one prefix in the area range matches an entry in the prefix list.
If all specific prefixes are denied by the prefix list, type 3 LSAs that correspond to the area range command will not be sent to any other area. Prefixes that are not permitted by the prefix list are implicitly denied.
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the area filter-list command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example filters prefixes that are sent from all other areas to area 1:
area 1 filter-list prefix AREA_1 inRelated Commands
area nssa
To configure an area as a not-so-stubby area (NSSA), use the area nssa command in router address family topology or router configuration mode. To remove the NSSA distinction from the area, use the no form of this command.
area area-id nssa [no-redistribution] [default-information-originate [metric] [metric-type]] [no-summary]
no area area-id nssa [no-redistribution] [default-information-originate [metric] [metric-type]] [no-summary]
Syntax Description
Command Default
No NSSA area is defined.
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
To remove the specified area from the software configuration, use the no area area-id command (with no other keywords). That is, the no area area-id command removes all area options, such as area authentication, area default-cost, area nssa, area range, area stub, and area virtual-link.
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the area nssa command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example makes area 1 an NSSA area:
router ospf 1redistribute rip subnetsnetwork 172.19.92.0 0.0.0.255 area 1area 1 nssaRelated Commands
redistribute
Redistributes routes from one routing domain into another routing domain.
area nssa translate
To configure an area as a not-so-stubby area (NSSA) and to configure the OSPF Forwarding Address Suppression in Translated Type-5 LSAs feature, use the area nssa translate command in router address family topology or router configuration mode. To remove the NSSA distinction from the area, use the no form of this command.
area area-id nssa translate type7 suppress-fa
no area area-id nssa translate type7 suppress-fa
Syntax Description
Command Default
No translation occurs.
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
To configure the OSPF Forwarding Address Suppression in Translated Type-5 LSAs feature, configure the translate type7 suppress-fa keywords. Consider the following caution.
Caution
If the translate keyword is used in addition to the no-redistribution or default-information-originate keywords, two separate lines for the area nssa command appear in the configuration file for ease of readability. For example, if the area 6 nssa no-redistribution translate type7 suppress-fa command is configured, the following lines would appear in the configuration file:
router ospf 1area 6 nssa no-redistributionarea 6 nssa translate type7 suppress-faTo remove the specified area from the software configuration, use the no area area-id command (with no other keywords). That is, the no area area-id command removes all area options, such as area authentication, area default-cost, area nssa, area range, area stub, and area virtual-link.
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the area nssa translate command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example causes OSPF to translate Type-7 LSAs from area 1 to Type-5 LSAs, but not place the Type-7 forwarding address into the Type-5 LSAs. OSPF places 0.0.0.0 as the forwarding address in the Type-5 LSAs.
router ospf 2network 172.19.92.0 0.0.0.255 area 1area 1 nssa translate type7 suppress-faRelated Commands
redistribute
Redistributes routes from one routing domain into another routing domain.
area range
To consolidate and summarize routes at an area boundary, use the area range command in router address family topology or router configuration mode. To disable this function, use the no form of this command.
area area-id range ip-address ip-address-mask [advertise | not-advertise] [cost cost]
no area area-id range ip-address ip-address-mask [advertise | not-advertise] [cost cost]
Syntax Description
Command Default
This command is disabled by default.
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
The area range command is used only with Area Border Routers (ABRs). It is used to consolidate or summarize routes for an area. The result is that a single summary route is advertised to other areas by the ABR. Routing information is condensed at area boundaries. External to the area, a single route is advertised for each address range. This behavior is called route summarization.
Multiple area range router configuration commands can be configured. Thus, OSPF can summarize addresses for many different sets of address ranges.
Note
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the area range command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example specifies one summary route to be advertised by the ABR to other areas for all subnets on network 10.0.0.0 and for all hosts on network 192.168.110.0:
interface ethernet 0ip address 192.168.110.201 255.255.255.0!interface ethernet 1ip address 192.168.120.201 255.255.255.0!router ospf 201network 192.168.110.0 0.0.0.255 area 0area 10.0.0.0 range 10.0.0.0 255.0.0.0area 0 range 192.168.110.0 255.255.0.0Related Commands
area range (IPv6)
Consolidates and summarizes routes at an area boundary in an IPv6 network.
area sham-link
To configure a sham link interface on a provider edge (PE) router in a Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) backbone, use the area sham-link command in global configuration mode. To remove the sham link, use the no form of this command.
area area-id sham-link source-address destination-address [cost number] [ttl-security hops hop-count]
no area area-id sham-link source-address destination-address
Syntax Description
Command Default
No default behavior or values.
Command Modes
Global configuration (config-router)
Command History
Usage Guidelines
In the MPLS VPN environment, several VPN client sites can be connected in the same Open Shortest Path First (OSPF) area. If these sites are connected over a backdoor link in addition to the VPN backbone, all traffic passes over the backdoor link instead of over the VPN backbone. OSPF always selects intra-area routes over interarea (external) routes.
To correct this default OSPF behavior in an MPLS VPN, use the area sham-link command to configure a sham link between two PEs to connect the sites through the MPLS VPN backbone. A sham link represents an intra-area (unnumbered point-to-point) connection between PEs. All other routers in the area use the sham link to calculate intra-area shortest path first (SPF) routes to the remote site.
Configure the source and destination addresses of the sham link as a host route mask (255.255.255.255) on the PE routers that serve as the endpoints of the sham link. The source and destination IP addresses must belong to the VRF and be advertised by Border Gateway Protocol (BGP) to remote PE routers. The sham link endpoint addresses should not be advertised by OSPF.
Examples
The following example shows how to configure a sham link between two PE routers in an MPLS VPN backbone by using the area sham-link command on each router:
Router1(config)# interface loopback 55Router1(config-if)# ip vrf forwarding v1Router1(config-if)# ip address 10.0.0.1 255.255.255.255Router1(config-if)# exitRouter1(config)# router ospf 2 vrf v1Router1(config-router)# log-adjacency-changesRouter1(config-router)# area 120 sham-link 10.0.0.1 10.44.0.1 cost 1Router1(config-router)# redistribute bgp 1 subnetsRouter1(config-router)# network 10.2.0.1 255.255.255.255 area 1Router1(config-router)# network 10.120.0.0 0.255.255.255 area 120Router1(config-router)# network 10.140.0.0 0.255.255.255 area 120Router1(config-router)# exitRouter2(config)# interface loopback 44Router2(config-if)# ip vrf forwarding v1Router2(config-if)# ip address 172.16.0.1 255.255.255.255Router1(config-if)# exitRouter2(config)# router ospf 2 vrf v1Router2(config-router)# log-adjacency-changesRouter2(config-router)# area 120 sham-link 10.44.0.1 10.0.0.1 cost 1Router2(config-router)# redistribute bgp 1 subnetsRouter2(config-router)# network 10.2.0.1 255.255.255.255 area 1Router2(config-router)# network 10.120.0.0 0.255.255.255 area 120Router2(config-router)# network 10.140.0.0 0.255.255.255 area 120area stub
To define an area as a stub area, use the area stub command in router address family topology or router configuration mode. To disable this function, use the no form of this command.
area area-id stub [no-summary]
no area area-id stub [no-summary]
Syntax Description
area-id
Identifier for the stub area; either a decimal value or an IP address.
no-summary
(Optional) Prevents an Area Border Router (ABR) from sending summary link advertisements into the stub area.
Defaults
No stub area is defined.
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
You must configure the area stub command on all routers and access servers in the stub area. Use the area router configuration command with the default-cost keyword to specify the cost of a default internal route sent into a stub area by an ABR.
There are two stub area router configuration commands: the stub and default-cost options of the area router configuration command. In all routers attached to the stub area, the area should be configured as a stub area using the stub keyword of the area command. Use the default-cost keyword only on an ABR attached to the stub area. The default-cost keyword provides the metric for the summary default route generated by the ABR into the stub area.
To further reduce the number of link-state advertisements (LSAs) sent into a stub area, you can configure the no-summary keyword on the ABR to prevent it from sending summary LSAs (LSA type 3) into the stub area.
Note
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the area stub command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example assigns a default cost of 20 to stub network 10.0.0.0:
interface ethernet 0ip address 10.56.0.201 255.255.0.0!router ospf 201network 10.0.0.0 0.255.255.255 area 10.0.0.0area 10.0.0.0 stubarea 10.0.0.0 default-cost 20Related Commands
area authentication
Enables authentication for an OSPF area.
area default-cost
Specifies a cost for the default summary route sent into a stub area.
area virtual-link
To define an Open Shortest Path First (OSPF) virtual link, use the area virtual-link command in router address family topology or router configuration mode. To remove a virtual link, use the no form of this command.
area area-id virtual-link router-id [hello-interval seconds] [retransmit-interval seconds] [transmit-delay seconds] [dead-interval seconds] [ttl-security hops hop-count]
no area area-id virtual-link router-id [hello-interval] [retransmit-interval] [transmit-delay] [dead-interval] [ttl-security]
Syntax Description
Command Default
area-id: No area ID is predefined.
router-id: No router ID is predefined.Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
In OSPF, all areas must be connected to a backbone area. If the connection to the backbone is lost, it can be repaired by establishing a virtual link.
The smaller the hello interval, the faster topological changes will be detected, but more routing traffic will ensue.
The setting of the retransmit interval should be conservative, or needless retransmissions will result. The value should be larger for serial lines and virtual links.
The transmit delay value should take into account the transmission and propagation delays for the interface.
To configure a virtual link in OSPF for IPv6, you must use a router ID instead of an address. In OSPF for IPv6, the virtual link takes the router ID rather than the IPv6 prefix of the remote router.
Note
Note
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the area virtual-link command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example establishes a virtual link with default values for all optional parameters:
ipv6 router ospf 1log-adjacency-changesarea 1 virtual-link 192.168.255.1The following example establishes a virtual link in OSPF for IPv6:
ipv6 router ospf 1log-adjacency-changesarea 1 virtual-link 192.168.255.1 hello-interval 5auto-cost
To control how Open Shortest Path First (OSPF) calculates default metrics for the interface, use the auto-cost command in router configuration mode. To assign cost based only on the interface type, use the no form of this command.
auto-cost reference-bandwidth mbps
no auto-cost reference-bandwidth
Syntax Description
reference-bandwidth mbps
Rate in Mbps (bandwidth). The range is from 1 to 4294967; the default is 100.
Defaults
100 Mbps
Command Modes
Router configuration
Command History
Usage Guidelines
In Cisco IOS Release 10.3 and later releases, by default OSPF will calculate the OSPF metric for an interface according to the bandwidth of the interface. For example, a 64K link will get a metric of 1562, and a T1 link will have a metric of 64.
The OSPF metric is calculated as the ref-bw value divided by the bandwidth, with mbps equal to 108 by default, and bandwidth determined by the bandwidth (interface) command. The calculation gives FDDI a metric of 1.
If you have multiple links with high bandwidth (such as FDDI or ATM), you might want to use a larger number to differentiate the cost on those links.
The value set by the ip ospf cost command overrides the cost resulting from the auto-cost command.
Examples
The following example changes the cost of the FDDI link to 10, while the gigabit Ethernet link remains at a cost of 1. Thus, the link costs are differentiated.
router ospf 1auto-cost reference-bandwidth 1000Related Commands
capability lls
To enable the use of the Link-Local Signalling (LLS) data block in originated Open Shortest Path First (OSPF) packets and reenable OSPF nonstop forwarding (NSF) awareness, use the capability lls command in router configuration mode. To disable LLS and OSPF NSF awareness, use the no form of this command.
capability lls
no capability lls
Syntax Description
This command has no arguments or keywords.
Command Default
LLS is enabled.
Command Modes
Router configuration
Command History
Usage Guidelines
You might want to disable NSF awareness by disabling the use of the LLS data block in originated OSPF packets. You might want to disable NSF awareness if the router has no applications using LLS.
If NSF is configured and you try to disable LLS, you will receive the error message, "OSPF Non-Stop Forwarding (NSF) must be disabled first."
If LLS is disabled and you try to configure NSF, you will receive the error message, "OSPF Link-Local Signaling (LLS) capability must be enabled first."
Examples
The following example disables LLS support and OSPF NSF awareness:
router ospf 2no capability llscapability transit
To reenable Open Shortest Path First (OSPF) area capability transit after it has been disabled, use the capability transit command in router configuration mode. To disable OSPF area capability transit on all areas for a router process, use the no form of this command.
capability transit
no capability transit
Syntax Description
This command has no arguments or keywords.
Defaults
OSPF area capability transit is enabled.
Command Modes
Router configuration
Command History
Usage Guidelines
OSPF area capability transit is enabled by default, allowing the OSPF Area Border Router to install better-cost routes to the backbone area through the transit area instead of the virtual links. If you want to retain a traffic pattern through the virtual-link path, you can disable capability transit by entering the no capability transit command. If paths through the transit area are discovered, they are most likely to be more optimal paths, or at least equal to, the virtual-link path. To reenable capability transit, enter the capability transit command.
If you need to verify whether OSPF area capability transit is enabled for a specific routing process, enter the show ip ospf command.
Examples
The following example shows how to disable OSPF area capability transit on all areas for a router process named ospf 1. A show ip ospf command is issued first to display the current areas that have area capability transit enabled. The no capability transit command is then entered to disable OSPF area capability transit on all areas for the router process ospf 1.
Router# show ip ospfRouting Process "ospf 1" with ID 10.1.1.1Supports only single TOS(TOS0) routesSupports opaque LSASupports Link-local Signaling (LLS)!Supports area transit capabilityIt is an area border routerInitial SPF schedule delay 5000 msecsMinimum hold time between two consecutive SPFs 10000 msecsMaximum wait time between two consecutive SPFs 10000 msecsMinimum LSA interval 5 secs. Minimum LSA arrival 1 secsLSA group pacing timer 240 secsInterface flood pacing timer 33 msecsRetransmission pacing timer 66 msecsNumber of external LSA 8. Checksum Sum 0x02853FNumber of opaque AS LSA 0. Checksum Sum 0x000000Number of DCbitless external and opaque AS LSA 0Number of DoNotAge external and opaque AS LSA 0Number of areas in this router is 2. 2 normal 0 stub 0 nssa!Number of areas transit capable is 1External flood list length 0Area BACKBONE(0)Number of interfaces in this area is 3Area has no authenticationSPF algorithm last executed 00:02:21.524 agoSPF algorithm executed 11 timesArea ranges areNumber of LSA 49. Checksum Sum 0x19B5FANumber of opaque link LSA 0. Checksum Sum 0x000000Number of DCbitless LSA 0Number of indication LSA 0Number of DoNotAge LSA 38Flood list length 0Area 1Number of interfaces in this area is 3!This area has transit capability: Virtual Link EndpointArea has no authenticationSPF algorithm last executed 00:02:36.544 agoSPF algorithm executed 9 timesArea ranges areNumber of LSA 42. Checksum Sum 0x1756D5Number of opaque link LSA 0. Checksum Sum 0x000000Number of DCbitless LSA 0Number of indication LSA 0Number of DoNotAge LSA 0Flood list length 0Router(config)# router ospf 1Router(router-config)# no capability transit
Related Commands
capability vrf-lite
To suppress the provider edge (PE) specific checks on a router when the Open Shortest Path First (OSPF) process is associated with the VPN routing and forwarding instance (VRF), use the capability vrf-lite command in router configuration mode. To restore the checks, use the no form of this command.
capability vrf-lite
no capability vrf-lite
Syntax Description
This command has no arguments or keywords.
Defaults
Disabled. PE specific checks are performed if the process is associated with VRF command modes.
Command Modes
Router configuration
Command History
Usage Guidelines
This command works only if the OSPF process is associated with the VRF.
