Cisco IOS IP and IP Routing Command Reference, Release 12.1
OSPF Commands

Table Of Contents

OSPF Commands

area authentication

area default-cost

area nssa

area range

area stub

area virtual-link

auto-cost

clear ip ospf

compatible rfc1583

default-information originate (OSPF)

default-metric (OSPF)

distance ospf

domain-tag

ignore lsa mospf

ip ospf authentication

ip ospf authentication-key

ip ospf cost

ip ospf database-filter

ip ospf dead-interval

ip ospf demand-circuit

ip ospf hello-interval

ip ospf message-digest-key

ip ospf mtu-ignore

ip ospf name-lookup

ip ospf network

ip ospf priority

ip ospf retransmit-interval

ip ospf transmit-delay

log-adjacency-changes

neighbor (OSPF)

neighbor database-filter

network area

router-id

router ospf

show ip ospf

show ip ospf border-routers

show ip ospf database

show ip ospf flood-list

show ip ospf interface

show ip ospf neighbor

show ip ospf request-list

show ip ospf retransmission-list

show ip ospf summary-address

show ip ospf virtual-links

summary-address (OSPF)

timers lsa-group-pacing

timers spf


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 and IP Routing Configuration Guide.

area authentication

To enable authentication for an OSPF area, use the area authentication command in router configuration mode. To remove an area's authentication specification 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

no area area-id

Syntax Description

area-id

Identifier of the area for which authentication is to be enabled. The identifier can be specified as either a decimal value or an IP address.

message-digest

(Optional) Enables MD5 authentication on the area specified by area-id.


Defaults

Type 0 authentication (no authentication)

Command Modes

Router configuration

Command History

Release
Modification

10.0

This command was introduced.

11.0

The message-digest keyword was added.


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 area's authentication specification, 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, no area area-id 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 0
 ip address 192.168.251.201 255.255.255.0
 ip ospf authentication-key adcdefgh
!
interface ethernet 1
 ip address 10.56.0.201 255.255.0.0
 ip ospf authentication-key ijklmnop
!
router ospf 201
 network 10.0.0.0 0.255.255.255 area 10.0.0.0
 network 192.168.0.0 0.0.255.255 area 0
 area 10.0.0.0 authentication
 area 0 authentication

Related Commands

Command
Description

area default-cost

Specifies a cost for the default summary route sent into a stub area.

area stub

Defines an area as a stub area.

ip ospf authentication-key

Assigns a password to be used by neighboring routers that are using the simple password authentication of OSPF.

ip ospf message-digest-key

Enables OSPF MD5 authentication.


area default-cost

To specify a cost for the default summary route sent into a stub or NSSA area, 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

area-id

Identifier for the stub or NSSA area. The identifier can be specified as either a decimal value or as an IP address.

cost

Cost for the default summary route used for a stub or NSSA area. The acceptable value is a 24-bit number.


Defaults

cost: 1

Command Modes

Router configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

The command is used only on an area border router attached to a stub or NSSA area.

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 area border router attached to the stub area. The default-cost option provides the metric for the summary default route generated by the area border router into the stub area.


Note To remove the specified area from the software configuration, use the no area area-id command (with no other keywords). That is, no area area-id 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 assigns a default-cost of 20 to stub network 10.0.0.0:

interface ethernet 0
 ip address 10.56.0.201 255.255.0.0
!
router ospf 201
 network 10.0.0.0 0.255.255.255 area 10.0.0.0
 area 10.0.0.0 stub
 area 10.0.0.0 default-cost 20

Related Commands

Command
Description

area authentication

Enables authentication for an OSPF area.

area stub

Defines an area as a stub area.


area 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 area area-id

Syntax Description

area-id

Identifier of the area for which authentication is to be enabled. The identifier can be specified as either a decimal value or an IP address.

no-redistribution

(Optional) Used when the router is a NSSA ABR and you want the redistribute command to import routes only into the normal areas, but not into the NSSA area.

default-information-
originate

(Optional) Used to generate a Type 7 default into the NSSA area. This argument takes effect only on NSSA ABR or NSSA ASBR.

metric

OSPF default metric.

metric-type

OSPF metric type for default routes.

no-summary

(Optional) Allows an area to be a not-so-stubby area but not have summary routes injected into it.


Defaults

No NSSA area is defined.

Command Modes

Router configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines


Note To remove the specified area from the software configuration, use the no area area-id command (with no other keywords). That is, no area area-id 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 1
 redistribute rip subnets
 network 172.19.92.0.0.0.0.255 area 1
 area 1 nssa

area 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 address mask [advertise | not-advertise]

no area area-id range address mask [advertise | not-advertise]

no area area-id

Syntax Description

area-id

Identifier of the area about which routes are to be summarized. It can be specified as either a decimal value or as an IP address.

address

IP address.

mask

IP mask.

advertise

(Default) Sets the address range status to advertise and generates a Type 3 summary LSA.

not-advertise

Sets the address range status to DoNotAdvertise. The Type 3 summary LSA is suppressed and the component networks remain hidden from other networks.


Defaults

This command is disabled by default.

Command Modes

Router configuration

Command History

Release
Modification

10.0

This command was introduced.


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 To remove the specified area from the software configuration, use the no area area-id command (with no other keywords). That is, no area area-id 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 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 0
 ip address 192.168.110.201 255.255.255.0
!
interface ethernet 1
 ip address 192.168.120.201 255.255.255.0
!
router ospf 201
 network 192.168.110.0 0.0.0.255 area 0
 area 10.0.0.0 range 10.0.0.0 255.0.0.0
 area 0 range 192.168.110.0 255.255.0.0

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 area area-id

Syntax Description

area-id

Identifier for the stub area; either a decimal value or an IP address.

no-summary

(Optional) Prevents an ABR from sending summary link advertisements into the stub area.


Defaults

No stub area is defined.

Command Modes

Router configuration

Command History

Release
Modification

10.0

This command was introduced.


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 area border router.

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 area border router into the stub area.

To further reduce the number of link state advertisements (LSAs) sent into a stub area, you can configure no-summary on the ABR to prevent it from sending summary LSAs (LSA type 3) into the stub area.


Note To remove the specified area from the software configuration, use the no area area-id command (with no other keywords). That is, no area area-id 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 assigns a default cost of 20 to stub network 10.0.0.0:

interface ethernet 0
 ip address 10.56.0.201 255.255.0.0
!
router ospf 201
 network 10.0.0.0 0.255.255.255 area 10.0.0.0
 area 10.0.0.0 stub
 area 10.0.0.0 default-cost 20

Related Commands

Command
Description

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 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 keyid 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 keyid md5 key]]

no area area-id

Syntax Description

area-id

Area ID assigned to the transit area for the virtual link. This can be either a decimal value or a valid IP address. There is no default.

router-id

Router ID associated with the virtual link neighbor. The router ID appears in the show ip ospf display. It is internally derived by each router from the router's interface IP addresses. This value must be entered in the format of an IP address. There is no default.

authentication

(Optional) Specifies authentication type.

message-digest

(Optional) Specifies that message-digest authentication is used.

null

(Optional) No authentication is used. Overrides password or message-digest authentication if configured for the area.

hello-interval seconds

(Optional) Time in seconds between the hello packets that the Cisco IOS software sends on an interface. Unsigned integer value to be advertised in the software's hello packets. The value must be the same for all routers and access servers attached to a common network. The default is 10 seconds.

retransmit-interval seconds

(Optional) Time in seconds between link state advertisement retransmissions for adjacencies belonging to the interface. Expected round-trip delay between any two routers on the attached network. The value must be greater than the expected round-trip delay. The default is 5 seconds.

transmit-delay seconds

(Optional) Estimated time in seconds required to transmit a link state update packet on the interface. Integer value that must be greater than zero. Link state advertisements in the update packet have their age incremented by this amount before transmission. The default value is 1 second.

dead-interval seconds

(Optional) Time in seconds that hello packets are not seen before its neighbors declare the router down. Unsigned integer value. The default is four times the hello interval, or 40 seconds. As with the hello interval, this value must be the same for all routers and access servers attached to a common network.

authentication-key key

(Optional) Password to be used by neighboring routers. Any continuous string of characters that you can enter from the keyboard up to 8 bytes long. This string acts as a key that will allow the authentication procedure to generate or verify the authentication field in the OSPF header. This key is inserted directly into the OSPF header when originating routing protocol packets. A separate password can be assigned to each network on a per-interface basis. All neighboring routers on the same network must have the same password to be able to route OSPF traffic. The password is encrypted in the configuration file if the service password-encryption command is enabled. There is no default value.

message-digest-key keyid md5 key

(Optional) Key identifier and password to be used by neighboring routers and this router for MD5 authentication. The key-id argument is a number in the range 1 to 255. The key is an alphanumeric string of up to 16 characters. All neighboring routers on the same network must have the same key identifier and key to be able to route OSPF traffic. There is no default value.


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

Release
Modification

10.0

This command was introduced.

11.0

The message-digest-key key-id md5 key keywords and arguments were added.

12.0

The authentication, message-digest, and null keywords were added.


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.


Note Each virtual link neighbor must include the transit area ID and the corresponding virtual link neighbor's router ID in order for a virtual link to be properly configured. Use the show ip ospf EXEC command to see the router ID.



Note To remove the specified area from the software configuration, use the no area area-id command (with no other keywords). That is, no area area-id 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 establishes a virtual link with default values for all optional parameters:

router ospf 201
 network 10.0.0.0 0.255.255.255 area 10.0.0.0
 area 10.0.0.0 virtual-link 10.3.4.5

The following example establishes a virtual link with MD5 authentication:

router ospf 201
 network 10.0.0.0 0.255.255.255 area 10.0.0.0
 area 10.0.0.0 virtual-link 10.3.4.5 message-digest-key 3 md5 sa5721bk47

Note If MD5 authentication is used for the virtual link, then all other routers in area 0 must use MD5 authentication.


Related Commands

Command
Description

area authentication

Enables authentication for an OSPF area.

service password-encryption

Encrypts passwords.

show ip ospf

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 megabits per second (bandwidth). The range is 1 to 4294967; the default is 100.


Defaults

100 megabits per second

Command Modes

Router configuration

Command History

Release
Modification

11.2

This command was introduced.


Usage Guidelines

In Cisco IOS Release 10.3 and later, 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 ref-bw divided by 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 1
 auto-cost reference-bandwidth 1000

Related Commands

Command
Description

ip ospf cost

Explicitly specifies the cost of sending a packet on an interface.


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 [intf] [nbr-id]]}

Syntax Description

pid

(Optional) Process ID.

process

Reset OSPF process.

redistribution

Clear OSPF route redistribution.

counters

OSPF counters.

neighbor

N(Optional) Neighbor statistics per interface.

intf

(Optional) Neighbor interface.

nbr-id

(Optional) Neighbor ID.


Command Modes

Privileged EXEC

Command History

Release
Modification

11.1

This command was introduced.


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 process
 !

compatible 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

Release
Modification

12.1 (2)T

This command was introduced.


Usage Guidelines

This command is back compatible to 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

always

(Optional) Always advertises the default route regardless of whether the software has a default route.

metric metric-value

(Optional) Metric used for generating the default route. If you omit a value and do not specify a value using the default-metric router configuration command, the default metric value is 1. The value used is specific to the protocol.

metric-type type-value

(Optional) External link type associated with the default route advertised into the OSPF routing domain. It can be one of the following values:

1—Type 1 external route

2—Type 2 external route

The default is type 2 external route.

route-map map-name

(Optional) Routing process will generate the default route if the route map is satisfied.


Defaults

This command is disabled by default.

Command Modes

Router configuration

Command History

Release
Modification

10.0

This command was introduced.


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:

If you use the ip prefix-list command with the default-information originate command to generate default routes, specify only IP adress matching. Avoid using the ge and le keywords.

For example, the following command works:

ip prefix-list anyrtcondition seq 5 permit 0.0.0.0/0

However, the following command is not supported:

ip prefix-list anyrtcondition seq 5 permit 0.0.0.0/0 le 32

Using the ip prefix-list command with the route-map and match ip next-hop commands is not supported. Only IP address match clauses are supported.

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 109
 redistribute igrp 108 metric 100 subnets
 default-information originate metric 100 metric-type 1

Related Commands

Command
Description

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 this form of the default-metric command in router configuration mode. To return to the default state, use the no form of this command.

default-metric number

no default-metric number

Syntax Description

number

Default metric value appropriate for the specified routing protocol.


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

Release
Modification

10.0

This command was introduced.


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 When enabled, the default-metric command applies a metric value of 0 to redistributed connected routes. The default-metric command does not override metric values that are applied with the redistribute command.


Examples

The following example shows a router in autonomous system 109 using both the RIP and the OSPF routing protocols. The example advertises OSPF-derived routes using the RIP protocol and assigns the IGRP-derived routes a RIP metric of 10.

router rip
 default-metric 10
 redistribute ospf 109

Related Commands

Command
Description

redistribute (IP)

Redistributes routes from one routing domain into another routing domain.


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

intra-area dist1

(Optional) Sets the distance for all routes within an area. The default value is 110.

inter-area dist2

(Optional) Sets the distance for all routes from one area to another area. The default value is 110.

external dist3

(Optional) Sets the distance for routes from other routing domains, learned by redistribution. The default value is 110.


Defaults

dist1: 110

dist2: 110

dist3: 110

Command Modes

Router configuration

Command History

Release
Modification

11.1(14)

This command was introduced.


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

router ospf 1
 redistribute ospf 2 subnet
 distance ospf external 200
!
router ospf 2
 redistribute ospf 1 subnet
 distance ospf external 200

Router B

router ospf 1 
 redistribute ospf 2 subnet
 distance ospf external 200 
! 
router ospf 2
 redistribute ospf 1 subnet
 distance ospf external 200

Related Commands

Command
Description

distance (IP)

Defines an administrative distance.


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.

domain-tag tag-value

no domain-tag tag-value

Syntax Description

tag-value

Tag value. A 32-bit value entered in decimal format. The default value is calculated based on the Border Gateway Protocol (BGP) autonomous system (AS) number of the Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) backbone. The four highest bits are set to 1101 according to RFC 1745. The lowest 16 bits map the BGP AS number of the MPLS VPN backbone. If a user specifies the tag-value, the value does not have to follow any particular format.


Defaults

The default value is calculated based on the BGP autonomous system number of the MPLS VPN backbone. The four highest bits are set to 1101 according to RFC 1745. The lowest 16 bits map the BGP autonomous system number of the MPLS VPN backbone.

Command Modes

Router configuration

Command History

Release
Modification

12.1(7)

The command was introduced.

12.1(7)E

The command was integrated into Cisco IOS Release 12.1(7)E.

12.1(7)EC

The command was integrated into Cisco IOS Release 12.1(7)EC.

12.0(17)ST

This command was integrated into Cisco IOS Release 12.0(17)ST.

12.2(2)B

The command was integrated into Cisco IOS Release 12.2(4)B.

12.2(14)S

The command was integrated into Cisco IOS Release 12.2(14)S.


Usage Guidelines

When OSPF is used between a PE router and a CE router, BGP routes that come from the MPLS backbone are redistributed to OSPF. These redistributed routes can be announced in Type-3, Type-5, or Type-7 LSAs. If the redistribution of the BGP routes results in Type-5 or Type-7 LSAs, the External Route Tag will be set to the value of the tag. If another PE router receives a Type-5 or Type-7 LSA with an External Route Tag equal to the set tag value, it will ignore the LSA, therefore preventing the redistributed routes that originated from the MPLS backbone from returning via some other location on the MPLS backbone.

Examples

The following example configures the tag value 777:

Router(config)# router ospf 10 vrf grc
Router(config-router)# domain-tag 777

The show ip ospf database command is entered to verify that the tag value 777 has been applied to the External Route Tag:

Router# show ospf database external 192.168.50.1

            OSPF Router with ID (192.168.239.66) (Process ID 10)

               Type-5 AS External Link States

  LS age: 18
  Options: (No TOS-capability, DC)
  S Type: AS External Link
  Link State ID: 192.168.238.1 (External Network Number )
  Advertising Router: 192.168.239.66
  LS Seq Number: 80000002
  Checksum: 0xDAB0
  Length: 36
  Network Mask: /32
        Metric Type: 2 (Larger than any link state path)
        TOS: 0 
        Metric: 1 
        Forward Address: 0.0.0.0
        External Route Tag: 777
.
.
.
              OSPF Router with ID (198.168.237.56) (Process ID 1)

Related Commands

Command
Description

show ospf database

Displays lists of information related to the OSPF database for a specific router.


ignore lsa mospf

To suppress the sending of syslog messages when the router receives LSA Type 6 (MOSPF) packets, which are unsupported, use the ignore lsa mospf command in router configuration mode. To restore the sending of syslog messages, use the no form of this command.

ignore lsa mospf

no ignore lsa mospf

Syntax Description

This command has no arguments or keywords.

Defaults

This command is disabled by default. Each MOSPF packet causes the router to send a syslog message.

Command Modes

Router configuration

Command History

Release
Modification

11.1

This command was introduced.


Usage Guidelines

Cisco routers do not support LSA Type 6 (MOSPF), and they generate syslog messages if they receive such packets. If the router is receiving many MOSPF packets, you might want to configure the router to ignore the packets and thus prevent a large number of syslog messages.

Examples

The following example configures the router to suppress the sending of syslog messages when it receives MOSPF packets:

router ospf 109
 ignore lsa mospf

ip ospf authentication

To specify the authentication type for an interface, use the ip ospf authentication command in interface configuration mode. To remove the authentication type for an interface, use the no form of this command.

ip ospf authentication [message-digest | null]

no ip ospf authentication

Syntax Description

message-digest

(Optional) Specifies that message-digest authentication will be used.

null

(Optional) No authentication is used. Useful for overriding password or message-digest authentication if configured for an area.


Defaults

The area default is no authentication (null authentication).

Command Modes

Interface configuration

Command History

Release
Modification

12.0

This command was introduced.


Usage Guidelines

Before using the ip ospf authentication command, configure a password for the interface using the ip ospf authentication-key command. If you use the ip ospf authentication message-digest command, configure the message-digest key for the interface with the ip ospf message-digest-key command.

For backward compatibility, authentication type for an area is still supported. If the authentication type is not specified for an interface, the authentication type for the area will be used (the area default is null authentication).

Examples

The following example enables message digest authentication:

ip ospf authentication message-digest

Related Commands

Command
Description

area authentication

Enables authentication for an OSPF area.

ip ospf authentication-key

Assigns a password to be used by neighboring routers that are using the simple password authentication of OSPF.

ip ospf message-digest-key

Enables OSPF MD5 authentication.


ip ospf authentication-key

To assign a password to be used by neighboring routers that are using the OSPF simple password authentication, use the ip ospf authentication-key command in interface configuration mode. To remove a previously assigned OSPF password, use the no form of this command.

ip ospf authentication-key password

no ip ospf authentication-key

Syntax Description

password

Any continuous string of characters that can be entered from the keyboard up to 8 bytes in length.


Defaults

No password is specified.

Command Modes

Interface configuration

Command History

Release
Modification

10.0

This command was introduced.


Usage Guidelines

The password created by this command is used as a "key" that is inserted directly into the OSPF header when the Cisco IOS software originates routing protocol packets. A separate password can be assigned to each network on a per-interface basis. All neighboring routers on the same network must have the same password to be able to exchange OSPF information.


Note The Cisco IOS software will use this key only when authentication is enabled for an area with the area authentication router configuration command.


Examples

The following example enables the authentication key with the string yourpass:

ip ospf authentication-key yourpass

Related Commands

Command
Description

area authentication

Enables authentication for an OSPF area.

ip ospf authentication