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Cisco IOS IP Command Reference, Volume 2 of 3: Routing Protocols, Release 12.2
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About Cisco IOS Software Documentation
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Using Cisco IOS Software
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On-Demand Routing Commands
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RIP Commands
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IGRP Commands
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OSPF commands
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EIGRP Commands
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Integrated IS-IS Commands
- Part 1: BGP Commands
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Multiprotocol BGP Extensions for IP Multicast Commands
- Part 2: IP Routing Protocol-Independent Commands
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Index - 12.2 - IP Routing Protocols Command Reference
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Table Of Contents
default-information originate (OSPF)
ip ospf database-filter all out
show ip ospf retransmission-list
OSPF Commands
Use the commands in this chapter to configure and monitor the Open Shortest Path First (OSPF) routing protocol. For OSPF configuration information and examples, refer to the "Configuring OSPF" chapter of the Cisco IOS IP Configuration Guide.
area authentication
To enable authentication for an 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 sent into a stub or not so stubby area (NSSA), use the area default-cost command in 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
Defaults
cost: 1
Command Modes
Router configuration
Command History
Usage Guidelines
The command is used only on an Area Border Router (ABR) attached to a stub 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
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 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. 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
Defaults
This command has no default behavior.
Command Modes
Router configuration
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 there is at least one prefix in the area range that 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.
Examples
The following example filters prefixes that are sent from all other areas to area 1:
area 1 filter-list prefix-list AREA_1 inarea nssa
To configure an area as a not-so-stubby area (NSSA), use the area nssa command in 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
Defaults
No NSSA area is defined.
Command Modes
Router configuration
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.
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 nssaarea range
To consolidate and summarize routes at an area boundary, use the area range command in router configuration mode. To disable this function, use the no form of this command.
area area-id range ip-address mask [advertise | not-advertise] [cost cost]
no area area-id range ip-address mask [advertise | not-advertise] [cost cost]
Syntax Description
Defaults
This command is disabled by default.
Command Modes
Router configuration
Command History
10.0
This command was introduced.
12.2
The cost cost keyword and argument were added.
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 router configuration commands specifying the range option can be configured. Thus, OSPF can summarize addresses for many different sets of address ranges.
Note
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 192.168.110.0 255.255.0.0 cost 60Related Commands
area stub
To define an area as a stub area, use the area stub command in 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 configuration
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 option to specify the cost of a default internal router 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 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.
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
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
Enables authentication for an OSPF area.
Specifies a cost for the default summary route sent into a stub area.
area virtual-link
To define an OSPF virtual link, use the area virtual-link command in router configuration mode with the optional parameters. To remove a virtual link, use the no form of this command.
area area-id virtual-link router-id [authentication [message-digest | null]] [hello-interval seconds] [retransmit-interval seconds] [transmit-delay seconds] [dead-interval seconds] [[authentication-key key] | [message-digest-key key-id md5 key]]
no area area-id virtual-link router-id [authentication [message-digest | null]] [hello-interval seconds] [retransmit-interval seconds] [transmit-delay seconds] [dead-interval seconds] [[authentication-key key] | [message-digest-key key-id md5 key]]
no area area-id
Syntax Description
Defaults
area-id: No area ID is predefined.
router-id: No router ID is predefined.
hello-interval seconds: 10 seconds
retransmit-interval seconds: 5 seconds
transmit-delay seconds: 1 second
dead-interval seconds: 40 seconds
authentication-key key: No key is predefined.
message-digest-key key-id md5 key: No key is predefined.Command Modes
Router configuration
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.
The Cisco IOS software will use the specified authentication key only when authentication is enabled for the backbone with the area area-id authentication router configuration command.
The two authentication schemes, simple text and MD5 authentication, are mutually exclusive. You can specify one or the other or neither. Any keywords and arguments you specify after authentication-key key or message-digest-key key-id md5 key are ignored. Therefore, specify any optional arguments before such a keyword-argument combination.
For Cisco IOS Release 12.2 and later releases, authentication type now is specified on a per-interface basis, rather than on a per-area basis, per RFC 2178. For backward compatability, authentication type for an area is still supported. If the authentication type is not specified for an interface, the interface will use the authentication type that was specified for the area. If no authentication type has been specified for the area, the area default is null authentication.
Note
Note
Examples
The following example establishes a virtual link with default values for all optional parameters:
router ospf 201network 10.0.0.0 0.255.255.255 area 10.0.0.0area 10.0.0.0 virtual-link 10.3.4.5The following example establishes a virtual link with MD5 authentication:
router ospf 201network 10.0.0.0 0.255.255.255 area 10.0.0.0area 10.0.0.0 virtual-link 10.3.4.5 message-digest-key 3 md5 sa5721bk47Related Commands
Enables authentication for an OSPF area.
service password-encryption
Encrypts passwords.
Displays general information about OSPF routing processes.
auto-cost
To control how 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 ref-bw
no auto-cost reference-bandwidth
Syntax Description
reference-bandwidth ref-bw
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 ref-bw equal to 108 by default, and bandwidth determined by the bandwidth 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
clear ip ospf
To clear redistribution based on the OSPF routing process ID, use the clear ip ospf command in privileged EXEC mode.
clear ip ospf [pid] {process | redistribution | counters [neighbor [neighbor-interface] [neighbor-id]]}
Syntax Description
Command Modes
Privileged EXEC
Command History
Usage Guidelines
Use the pid option to clear only one OSPF process. If the pid option is not specified, all OSPF processes are cleared.
Examples
The following example clears all OSPF processes:
clear ip ospf processcompatible rfc1583
To restore the method used to calculate summary route costs per RFC 1583, use the compatible rfc1583 command in router configuration mode. To disable RFC 1583 compatibility, use the no form of this command.
compatible rfc1583
no compatible rfc1583
Syntax Description
This command has no arguments or keywords.
Defaults
Compatible with RFC 1583.
Command Modes
Router configuration
Command History
Usage Guidelines
This command is backward compatible with Cisco IOS Release 12.0.
To minimize the chance of routing loops, all OSPF routers in an OSPF routing domain should have RFC compatibility set identically.
Because of the introduction of RFC 2328, OSPF Version 2, the method used to calculate summary route costs has changed. Use the no compatible rfc1583 command to enable the calculation method used per RFC 2328.
Examples
The following example specifies that the router process is compatible with RFC 1583:
router ospf 1 compatible rfc1583!default-information originate (OSPF)
To generate a default external route into an OSPF routing domain, use the default-information originate command in router configuration mode. To disable this feature, use the no form of this command.
default-information originate [always] [metric metric-value] [metric-type type-value] [route-map map-name]
no default-information originate [always] [metric metric-value] [metric-type type-value] [route-map map-name]
Syntax Description
Defaults
This command is disabled by default.
Command Modes
Router configuration
Command History
Usage Guidelines
Whenever you use the redistribute or the default-information router configuration command to redistribute routes into an OSPF routing domain, the Cisco IOS 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.
When you use this command for the OSPF process, the default network must reside in the routing table, and you must satisfy the route-map map-name keyword and argument. Use the default-information originate always route-map map-name form of the command when you do not want the dependency on the default network in the routing table.
Notes:
•
For example, the following command works:
ip prefix-list anyrtcondition seq 5 permit 0.0.0.0/0However, the following command is not supported:
ip prefix-list anyrtcondition seq 5 permit 0.0.0.0/0 le 32•
Examples
The following example specifies a metric of 100 for the default route redistributed into the OSPF routing domain and an external metric type of Type 1:
router ospf 109redistribute igrp 108 metric 100 subnetsdefault-information originate metric 100 metric-type 1Related Commands
redistribute (IP)
Redistributes routes from one routing domain into another routing domain.
default-metric (OSPF)
To set default metric values for the OSPF routing protocol, use the default-metric command in router configuration mode. To return to the default state, use the no form of this command.
default-metric metric-value
no default-metric metric-value
Syntax Description
Defaults
Built-in, automatic metric translations, as appropriate for each routing protocol. The metric of redistributed connected and static routes is set to 0.
Command Modes
Router configuration
Command History
Usage Guidelines
The default-metric command is used in conjunction with the redistribute router configuration 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, using a default metric provides a reasonable substitute and enables the redistribution to proceed.
Note
Examples
The following example shows a router in autonomous system 109 using both the Routing Information Protocol (RIP) and the OSPF routing protocols. The example advertises OSPF-derived routes using RIP and assigns the Internal Gateway Routing Protocol (IGRP)-derived routes a RIP metric of 10.
router ripdefault-metric 10redistribute ospf 109Related Commands
redistribute (IP)
Redistributes routes from one routing domain into another routing domain.
discard-route
To reinstall either an external or internal discard route that was previously removed, use the discard-route command in router configuration mode. To remove either an external or internal discard route, use the no form of this command.
discard-route [external | internal]
no discard-route [external | internal]
Syntax Description
Defaults
External and internal discard route entries are installed.
Command Modes
Router configuration
Command History
Usage Guidelines
External and internal discard route entries are installed in routing tables by default. During route summarization, routing loops may occur when data is sent to a nonexisting network that appears to be a part of the summary, and the router performing the summarization has a less specific route (pointing back to the sending router) for this network in its routing table. To prevent the routing loop, a discard route entry is installed in the routing table of the ABR or ASBR.
If for any reason you do not want to use the external or internal discard route, remove the discard route by entering the no discard-route command with either the external or internal keyword.
Examples
The following display shows the discard route functionality installed by default. When external or internal routes are summarized, a summary route to Null0 will appear in the router output from the show ip route command. See the router output lines that appear in bold font:
Router# show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGPD - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter areaN1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGPi - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2ia - IS-IS inter area, * - candidate default, U - per-user static routeo - ODR, P - periodic downloaded static routeGateway of last resort is not set172.16.0.0/24 is variably subnetted, 3 subnets, 2 masksC 172.16.0.128/25 is directly connected, Loopback1O 172.16.0.0/24 is a summary, 00:00:14, Null0C 172.16.0.0/25 is directly connected, Loopback0172.31.0.0/24 is variably subnetted, 3 subnets, 2 masksC 172.31.0.128/25 is directly connected, Loopback3O 172.31.0.0/24 is a summary, 00:00:02, Null0C 172.31.0.0/25 is directly connected, Loopback2C 192.168.0.0/24 is directly connected, Ethernet0/0RouterB# show ip route ospf172.16.0.0/24 is variably subnetted, 3 subnets, 2 masksO 172.16.0.0/24 is a summary, 00:00:29, Null0172.16.0.0/24 is variably subnetted, 3 subnets, 2 masksO 201.0.0.0/24 is a summary, 00:00:17, Null0When the no discard-route command with the internal keyword is entered, notice the following route change, indicated by the router output lines that appear in bold font:
RouterB# configure terminalEnter configuration commands, one per line. End with CNTL/Z.RouterB(config)# router ospf 1RouterB(config-router)# no discard-route internalRouterB(config-router)#endRouterB# show ip route ospf172.31.0.0/24 is variably subnetted, 3 subnets, 2 masksO 172.16.0.0/24 is a summary, 00:04:14, Null0Next, the no discard-route command with the external keyword is entered to remove the external discard route entry:
RouterB# configure terminalEnter configuration commands, one per line. End with CNTL/Z.RouterB(config)# router ospf 1RouterB(config-router)# no discard-route externalRouterB(config-router)# endThe following router output from the show running-config command confirms that both the external and internal discard routes have been removed from the routing table of RouterB. See the router output lines that appear in bold font:
RouterB# show running-configBuilding configuration...Current configuration : 1114 bytes!version 12.2service timestamps debug uptimeservice timestamps log uptimeno service password-encryption!hostname RouterB...router ospf 1log-adjacency-changesno discard-route externalno discard-route internalarea 1 range 172.16.0.0 255.255.255.0summary-address 172.31.0.0 255.255.255.0redistribute rip subnetsnetwork 192.168.0.0 0.0.0.255 area 0network 172.16.0.0 0.0.0.255 area 1!Related Commands
distance ospf
To define 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.
distance ospf {[intra-area dist1] [inter-area dist2] [external dist3]}
no distance ospf
Syntax Description
Defaults
dist1: 110
dist2: 110
dist3: 110
Command Modes
Router configuration
Command History
Usage Guidelines
You must specify at least one of the keyword-argument pairs.
This command performs the same function as the distance command used with an access list. However, the distance ospf command allows you to set 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.
Examples
The following example changes the external distance to 200, making the route less reliable:
Router A Configuration
router ospf 1redistribute ospf 2 subnetdistance ospf external 200!router ospf 2redistribute ospf 1 subnetdistance ospf external 200Router B Configuration
router ospf 1 redistribute ospf 2 subnetdistance ospf external 200 ! router ospf 2redistribute ospf 1 subnetdistance ospf external 200Related Commands
domain-tag
To set the Open Shortest Path First (OSPF) domain tag value for Type-5 or Type-7 link-state advertisements (LSAs) when OSPF is used as a protocol between a provider edge (PE) router and customer edge (CE) router, use the domain-tag command in router configuration mode. To reinstate the default tag value, use the no form of this command.
