OSPF Commands

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

Syntax Description

area-id	Identifier for the stub 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 area. The acceptable value is a 24-bit number.

Defaults

Cost of 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 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 command no area area-id (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 36.0.0.0:

interface ethernet 0
 ip address 36.56.0.201 255.255.0.0
!
router ospf 201
 network 36.0.0.0 0.255.255.255 area 36.0.0.0
 area 36.0.0.0 stub
 area 36.0.0.0 default-cost 20

Related Commands

Command	Description
area authentication	Enables authentication for an OSPF area.
area stub	Defines an area as a stub area.

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 only takes effect on NSSA ABR.

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 command no area area-id (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 enables NSSA authentication on area 1:

router ospf1
 redistribute rip subnets
 network 172.19.92.0.0.0.0.255 area 1
 area 1 nssa

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

Disabled

Command Modes

Router configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

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 command no area area-id (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 36.0.0.0 and for all hosts on network 192.42.110.0:

interface ethernet 0
 ip address 192.42.110.201 255.255.255.0
!
interface ethernet 1
 ip address 36.56.0.201 255.255.0.0
!
router ospf 201
 network 36.0.0.0 0.255.255.255 area 36.0.0.0
 network 192.42.110.0 0.0.0.255 area 0
 area 36.0.0.0 range 36.0.0.0 255.0.0.0
 area 0 range 192.42.110.0 255.255.255.0

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 (LSA) 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 command no area area-id (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 36.0.0.0:

interface ethernet 0
 ip address 36.56.0.201 255.255.0.0
!
router ospf 201
 network 36.0.0.0 0.255.255.255 area 36.0.0.0
 area 36.0.0.0 stub
 area 36.0.0.0 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.

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 it takes 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 a software's 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 keyid 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 keyid md5 key: No key is predefined.

Command Modes

Router configuration

Command History

Release	Modification
10.0	This command was introduced.
11.0	The following keywords and arguments were added: message-digest-key keyid md5 key

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 keyid 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 command no area area-id (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 36.0.0.0 0.255.255.255 area 36.0.0.0
 area 36.0.0.0 virtual-link 36.3.4.5
 

The following example establishes a virtual link with MD5 authentication:

router ospf 201
 network 36.0.0.0 0.255.255.255 area 36.0.0.0
 area 36.0.0.0 virtual-link 36.3.4.5 message-digest-key 3 md5 sa5721bk47

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.

Syntax Description

pid	(Optional) Process ID.
process	Reset OSPF process.
redistribution	Clear OSPF route redistribution.
counters	OSPF counters.
neighbor	Neighbor statistics per interface.
intf	Neighbor interface.
nbr-id	Neighbor ID.

Command Modes

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
 !

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

To minimize the chance of routing loops, all OSPF routers in an OSPF routing domain should have RFC compatibility set identically.

Because of the new 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
 !

Syntax Description

originate	Causes the Cisco IOS software to generate a default external route into an OSPF domain if the software already has a default route and you want to propagate to other routers.
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 10. 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.
level-1	Level 1 routes are redistributed into other IP routing protocols independently. It specifies if IS-IS advertises network 0.0.0.0 into the Level 1 area.
level-1-2	Both Level 1 and Level 2 routes are redistributed into other IP routing protocols. It specifies if IS-IS advertises network 0.0.0.0 into both levels in a single command.
level-2	Level 2 routes are redistributed into other IP routing protocols independently. It specifies if IS-IS advertises network 0.0.0.0 into the Level 2 subdomain.
route-map map-name	(Optional) Routing process will generate the default route if the route map is satisfied.

Defaults

Disabled

Command Modes

Router configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

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. 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.

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.

Syntax Description

number

Default metric value appropriate for the specified routing protocol.

Defaults

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

Command Modes

Router configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

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.

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 it less trustworthy.

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.

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.

Syntax Description

cost	Unsigned integer value expressed as the link state metric. It can be a value in the range 1 to 65535.

Defaults

No default cost is predefined.

Command Modes

Interface configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

You can set the metric manually using this command, if you need to change the default. Using the bandwidth command changes the link cost as long as this command is not used.

The link state metric is advertised as the link cost in the router link advertisement. We do not support type of service (TOS), so you can assign only one cost per interface.

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

  10⁸ ÷ Bandwidth

Using this formula, the default path costs were calculated as noted in the following list. If these values do not suit your network, you can use your own method of calculating path costs.

• 56-kbps serial link—Default cost is 1785

• 64-kbps serial link—Default cost is 1562

• T1 (1.544-Mbps serial link)—Default cost is 65

• E1 (2.048-Mbps serial link)—Default cost is 48

• 4-Mbps Token Ring—Default cost is 25

• Ethernet—Default cost is 10

• 16-Mbps Token Ring—Default cost is 6

• FDDI—Default cost is 1

Examples

The following example sets the interface cost value to 65:

ip ospf cost 65

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled; all outgoing LSAs are flooded to the interface.

Command Modes

Interface configuration

Command History

Release	Modification
12.0	This command was introduced.

Usage Guidelines

Syntax Description

seconds

Unsigned integer that specifies the interval in seconds; the value must be the same for all nodes on the network.

Defaults

Syntax Description

This command has no arguments or keywords.

Defaults

The circuit is not a demand circuit.

Command Modes

Interface configuration

Command History

Release	Modification
11.2	This command was introduced.

Usage Guidelines

On point-to-point interfaces, only one end of the demand circuit must be configured with this command. Periodic hellos are suppressed and periodic refreshes of LSAs do not flood the demand circuit. It allows the underlying datalink layer to be closed when the topology is stable. In point-to-multipoint topology, only the multipoint end must configured with this command.

Examples

The following example sets the configures an ISDN on demand circuit:

router ospf1
 network 18.0.3.0.0.0.0.25 area 0
interface BRIO
 ip ospf demand-circuit

Syntax Description

seconds

Unsigned integer that specifies the interval in seconds. The value must be the same for all nodes on a specific network.

Defaults

10 seconds

Command Modes

Interface configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

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

Examples

The following example sets the interval between hello packets to 15 seconds:

interface ethernet 1
 ip ospf hello-interval 15

Related Commands

Command	Description
ip ospf dead-interval	Sets the time period for which hello packets must not have been seen before neighbors declare the router down.

Syntax Description

keyid	An identifier in the range 1 to 255.
key	Alphanumeric password of up to 16 bytes.

Defaults

OSPF MD5 authentication is disabled.

Command Modes

Interface configuration

Command History

Release	Modification
11.0	This command was introduced.

Usage Guidelines

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

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

interface ethernet 1
 ip ospf message-digest-key 100 md5 OLD
 

You change the configuration to the following:

interface ethernet 1
 ip ospf message-digest-key 101 md5 NEW
 

The system assumes its neighbors do not have the new key yet, so it begins a rollover process. It sends multiple copies of the same packet, each authenticated by different keys. In this example, the system sends out two copies of the same packet—the first one authenticated by key 100 and the second one authenticated by key 101.

Rollover allows neighboring routers to continue communication while the network administrator is updating them with the new key. Rollover stops once the local system finds that all its neighbors know the new key. The system detects that a neighbor has the new key when it receives packets from the neighbor authenticated by the new key.

After all neighbors have been updated with the new key, the old key should be removed. In this example, you would enter the following:

interface ethernet 1
 no ip ospf message-digest-key 100
 

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

We recommend that you not keep more than one key per interface. Every time you add a new key, you should remove the old key to prevent the local system from continuing to communicate with a hostile system that knows the old key. Removing the old key also reduces overhead during rollover.

Examples

The following example sets a new key 19 with the password 8ry4222:

interface ethernet 1
 ip ospf message-digest-key 10 md5 xvv560qle
 ip ospf message-digest-key 19 md5 8ry4222

Related Commands

Command	Description
area authentication	Enables authentication for an OSPF area.

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

This feature makes it easier to identify a router because it is displayed by name rather than by its router ID or neighbor ID.

Examples

The following example configures OSPF to look up DNS names for use in all OSPF show EXEC command displays:

ip ospf name-lookup

Syntax Description

broadcast	Sets the network type to broadcast.
non-broadcast	Sets the network type to NBMA.
point-to-multipoint [non-broadcast]	Sets the network type to point-to-multipoint. The optional non-broadcast keyword sets the point-to-multipoint network to be nonbroadcast. If you use the non-broadcast keyword, the neighbor command is required.

Defaults

Depends on the network type.

Command Modes

Interface configuration

Command History

Release	Modification
10.0	This command was introduced.
10.3	The point-to-multipoint keyword was added.
11.3 AA	The non-broadcast keyword used with the point-to-multipoint keyword was added.

Usage Guidelines

Using this feature, you can configure broadcast networks as nonbroadcast multiaccess (NBMA) networks when, for example, you have routers in your network that do not support multicast addressing. You can also configure nonbroadcast multiaccess networks (such as X.25, Frame Relay, and SMDS) as broadcast networks. This feature saves you from having to configure neighbors.

Configuring NBMA networks as either broadcast or nonbroadcast assumes that there are virtual circuits from every router to every router or fully meshed network. This is not true for some cases, for example, because of cost constraints or when you have only a partially meshed network. In these cases, you can configure the OSPF network type as a point-to-multipoint network. Routing between two routers that are not directly connected will go through the router that has virtual circuits to both routers. You do not need to configure neighbors when using this feature.

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

OSPF has two features related to point-to-multipoint networks. One feature applies to broadcast networks; the other feature applies to nonbroadcast networks.

• On point-to-multipoint, broadcast networks, you can use the neighbor command and you must specify a cost to that neighbor.

• On point to multipoint, nonbroadcast networks, you must use the neighbor command to identify neighbors. Assigning a cost to a neighbor is optional.

Examples

The following example sets your OSPF network as a broadcast network:

interface serial 0
 ip address 160.89.77.17 255.255.255.0
 ip ospf network broadcast
 encapsulation frame-relay
 

The following example illustrates a point-to-multipoint network with broadcast.

interface Serial0
 ip address 10.0.1.1 255.255.255.0
 encapsulation frame-relay
 ip ospf cost 100
 ip ospf network point-to-multipoint
 frame-relay map ip 10.0.1.3 202 broadcast
 frame-relay map ip 10.0.1.4 203 broadcast
 frame-relay map ip 10.0.1.5 204 broadcast
 frame-relay local-dlci 200
!
router ospf 1
 network 10.0.1.0 0.0.0.255 area 0
 neighbor 10.0.1.5 cost 5
 neighbor 10.0.1.4 cost 10

Related Commands

Command	Description
frame-relay map	Defines mapping between a destination protocol address and the DLCI used to connect to the destination address.
neighbor (OSPF)	Configures OSPF routers interconnecting to nonbroadcast networks.
x25 map	Sets up the LAN protocols-to-remote host mapping.

Syntax Description

number

8-bit unsigned integer that specifies the priority. The range is from 0 to 255.

Defaults

Priority of 1

Command Modes

Interface configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

When two routers attached to a network both attempt to become the designated router, the one with the higher router priority takes precedence. If there is a tie, the router with the higher router ID takes precedence. A router with a router priority set to zero is ineligible to become the designated router or backup designated router. Router priority is only configured for interfaces to multiaccess networks (in other words, not point-to-point networks).

This priority value is used when you configure OSPF for nonbroadcast networks using the neighbor router configuration command for OSPF.

Examples

The following example sets the router priority value to 4:

interface ethernet 0
 ip ospf priority 4

Related Commands

Command	Description
ip ospf network	Configures the OSPF network type to a type other than the default for a given medium.
neighbor (OSPF)	Configures OSPF routers interconnecting to nonbroadcast networks.

Syntax Description

seconds

Time in seconds between retransmissions. It must be greater than the expected round-trip delay between any two routers on the attached network. The range is 1 to 65535 seconds. The default is 5 seconds.

Defaults

5 seconds

Command Modes

Interface configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

When a router sends a link state advertisement (LSA) to its neighbor, it keeps the LSA until it receives back the acknowledgment. If it receives no acknowledgment in seconds, it will retransmit the LSA.

The setting of this parameter should be conservative, or needless retransmission will result. The value should be larger for serial lines and virtual links.

Examples

The following example sets the retransmit-interval value to 8 seconds:

interface ethernet 2
 ip ospf retransmit-interval 8

Syntax Description

seconds

Time in seconds that it takes to transmit a link state update.The range is 1 to 65535 seconds. The default is 1 second.

Defaults

1 second

Command Modes

Interface configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

Link state advertisements in the update packet must have their ages incremented by the amount specified in the seconds argument before transmission. The value assigned should take into account the transmission and propagation delays for the interface.

If the delay is not added before transmission over a link, the time in which the LSA propagates over the link is not considered. This setting has more significance on very low speed links.

Examples

The following example sets the retransmit-delay value to 3 seconds:

interface ethernet 0
 ip ospf transmit-delay 3

Syntax Description

ip-address	Interface IP address of the neighbor.
priority number	(Optional) 8-bit number indicating the router priority value of the nonbroadcast neighbor associated with the IP address specified. The default is 0. This keyword does not apply to point-to-multipoint interfaces.
poll-interval seconds	(Optional) Unsigned integer value reflecting the poll interval. RFC 1247 recommends that this value be much larger than the hello interval. The default is 120 seconds (2 minutes). This keyword does not apply to point-to-multipoint interfaces.
cost number	(Optional) Assigns a cost to the neighbor, in the form of an integer from 1 to 65535. Neighbors with no specific cost configured will assume the cost of the interface, based on the ip ospf cost command. On point-to-multipoint interfaces, this is the only keyword and argument that make sense. This keyword does not apply to NBMA networks.

Defaults

No configuration is specified.

Command Modes

Router configuration

Command History

Release	Modification
10.0	This command was introduced.
11.3 AA	The cost keyword was added.

Usage Guidelines

X.25 and Frame Relay provide an optional broadcast capability that can be configured in the map to allow OSPF to run as a broadcast network. At the OSPF level you can configure the router as a broadcast network. See the x25 map and frame-relay map commands in the "X.25 Commands" and "Frame Relay Commands" chapters, respectively, in the Wide-Area Networking Command Reference for more detail.

One neighbor entry must be included in the Cisco IOS software configuration for each known nonbroadcast network neighbor. The neighbor address has to be on the primary address of the interface.

If a neighboring router has become inactive (hello packets have not been seen for the Router Dead Interval period), it may still be necessary to send hello packets to the dead neighbor. These hello packets will be sent at a reduced rate called Poll Interval.

When the router first starts up, it sends only hello packets to those routers with non-zero priority; that is, routers that are eligible to become designated routers (DR) and backup designated routers (BDR). After DR and BDR are selected, DR and BDR will then start sending hello packets to all neighbors in order to form adjacencies.

Prior to Release 12.0, the neighbor command applied to NBMA networks only. With Release 12.0, the neighbor command applies to NBMA networks and point-to-multipoint networks. On NBMA networks, the cost keyword is not accepted.

Examples

The following example declares a router at address 131.108.3.4 on a nonbroadcast network, with a priority of 1 and a poll interval of 180 seconds:

router ospf
 neighbor 131.108.3.4 priority 1 poll-interval 180
 

The following example illustrates a point-to-multipoint network with nonbroadcast:

interface Serial0
ip address 10.0.1.1 255.255.255.0
ip ospf network point-to-multipoint non-broadcast
encapsulation frame-relay
no keepalive
frame-relay local-dlci 200
frame-relay map ip 10.0.1.3 202
frame-relay map ip 10.0.1.4 203
frame-relay map ip 10.0.1.5 204
no shut
!
router ospf 1
network 10.0.1.0 0.0.0.255 area 0
neighbor 10.0.1.3 cost 5
neighbor 10.0.1.4 cost 10
neighbor 10.0.1.5 cost 15

Related Commands

Command	Description
ip ospf priority	"Sets the router priority, which helps determine the designated router for this network."

Syntax Description

ip-address all out

IP address of the neighbor to which outgoing LSAs are blocked.

Defaults

Disabled; all outgoing LSAs are flooded to the neighbor.

Command Modes

Router configuration

Command History

Release	Modification
12.0	This command was introduced.

Usage Guidelines

This command performs the same function that the ip ospf database-filter command performs on an interface basis.

Examples

The following example prevents flooding of OSPF LSAs to point-to-multipoint networks to the neighbor at IP address 1.2.3.4:

router ospf 109
 neighbor 1.2.3.4 database-filter all out

Related Commands

Command	Description
ip ospf database-filter	Filters outgoing LSAs to an OSPF interface.

Syntax Description

address	IP address.
wildcard-mask	IP-address-type mask that includes "don't care" bits.
area-id	Area that is to be associated with the OSPF address range. It can be specified as either a decimal value or as an IP address. If you intend to associate areas with IP subnets, you can specify a subnet address as the area-id.

Defaults

Disabled

Command Modes

Router configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

The address and wildcard-mask arguments together allow you to define one or multiple interfaces to be associated with a specific OSPF area using a single command. Using the wildcard-mask allows you to define one or multiple interfaces to be associated with a specific OSPF area using a single command. If you intend to associate areas with IP subnets, you can specify a subnet address as the area-id.

For OSPF to operate on the interface, that interface's primary address must be covered by the network area command. If the network area command covers only the secondary address, it will not enable OSPF over that interface.

The Cisco IOS software sequentially evaluates the address/wildcard-mask pair for each interface as follows:

1. The wildcard-mask is logically ORed with the interface IP address.

2. The wildcard-mask is logically ORed with address in the network command.

3. The software compares the two resulting values.

4. If they match, OSPF is enabled on the associated interface and this interface is attached to the OSPF area specified.

There is no limit to the number of network area commands you can use on the router.

Note   Any individual interface can only be attached to a single area. If the address ranges specified for different areas overlap, the software will adopt the first area in the network command list and ignore the subsequent overlapping portions. In general, it is recommended that you devise address ranges that do not overlap in order to avoid inadvertent conflicts.

Examples

The following partial example initializes OSPF routing process 109, and defines four OSPF areas: 10.9.50.0, 2, 3, and 0. Areas 10.9.50.0, 2, and 3 mask specific address ranges, while area 0 enables OSPF for all other networks.

interface ethernet 0
 ip address 131.108.20.1 255.255.255.0
router ospf 109
 network 131.108.20.0  0.0.0.255 area 10.9.50.0
 network 131.108.0.0  0.0.255.255 area 2
 network 131.109.10.0  0.0.0.255 area 3
 network 0.0.0.0  255.255.255.255 area 0

Related Commands

Command	Description
router ospf	Configures an OSPF routing process.

Syntax Description

reference-bandwidth ref-bw

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

Defaults

100 Mbits

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, while 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 ospf 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
 ospf auto-cost reference-bandwidth 1000

Related Commands

Command	Description
ip ospf cost	Explicitly specifies the cost of sending a packet on an interface.

Syntax Description

This command has no arguments or keywords.

Defaults

Disabled; 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
 ospf ignore lsa mospf

Syntax Description

This command has no arguments or keywords.

Defaults

No such syslog message is sent.

Command Modes

Router configuration

Command History

Release	Modification
11.2	This command was introduced.

Usage Guidelines

Configure this command if you want to know about OSPF neighbor changes without turning on the debugging command debug ip ospf adjacency. The ospf log-adj-changes command provides a higher level view of changes to the state of the peer relationship with less output.

Examples

The following example configures the router to send a syslog message for any neighbor state changes:

ospf log-adj-changes

Syntax Description

ip-address

Router ID in IP address format.

Defaults

No OSPF routing process is defined.

Command Modes

Router configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

You can configure an arbitrary value in the ip-address format for each router. However, each router ID must be unique.

Syntax Description

process-id

Internally used identification parameter for an OSPF routing process. It is locally assigned and can be any positive integer. A unique value is assigned for each OSPF routing process.

Defaults

No OSPF routing process is defined.

Command Modes

Global configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

You can specify multiple OSPF routing processes in each router.

Examples

The following example configures an OSPF routing process and assign a process number of 109:

router ospf 109

Related Commands

Command	Description
network area	Defines the interfaces on which OSPF runs and defines the area ID for those interfaces.

Syntax Description

process-id

(Optional) Process ID. If this argument is included, only information for the specified routing process is included.

Command Modes

EXEC

Command History

Release	Modification
10.0	This command was introduced.

Examples

The following is sample output from the show ip ospf command when entered without a specific OSPF process ID:

Router# show ip ospf

 
Routing Process "ospf 201" with ID 192.42.110.200
Supports only single TOS(TOS0) route
It is an area border and autonomous system boundary router
Redistributing External Routes from,
   	igrp 200 with metric mapped to 2, includes subnets in redistribution
   	rip with metric mapped to 2
   	igrp 2 with metric mapped to 100
   	igrp 32 with metric mapped to 1
Number of areas in this router is 3
Area 192.42.110.0
   	Number of interfaces in this area is 1
   	Area has simple password authentication
   	SPF algorithm executed 6 times
 

Syntax Description

This command has no arguments or keywords.

Command Modes

Privileged EXEC

Command History

Release	Modification
10.0	This command was introduced.

Examples

The following is sample output from the show ip ospf border-routers command:

Router# show ip ospf border-routers

 
OSPF Process 109 internal Routing Table
 
Destination      Next Hop        Cost   Type     Rte Type Area           SPF No
 
160.89.97.53     144.144.1.53    10     ABR      INTRA    0.0.0.3        3
160.89.103.51    160.89.96.51    10     ABR      INTRA    0.0.0.3        3
160.89.103.52    160.89.96.51    20     ASBR     INTER    0.0.0.3        3
160.89.103.52    144.144.1.53    22     ASBR     INTER    0.0.0.3        3
 

Syntax Description

process-id	(Optional) Internal identification. It is locally assigned and can be any positive integer. The number used here is the number assigned administratively when enabling the OSPF routing process.
area-id	(Optional) Area number associated with the OSPF address range defined in the network router configuration command used to define the particular area.
link-state-id	(Optional) Portion of the Internet environment that is being described by the advertisement. The value entered depends on the advertisement's LS type. It must be entered in the form of an IP address. When the link state advertisement is describing a network, the link-state-id can take one of two forms: The network's IP address (as in type 3 summary link advertisements and in autonomous system external link advertisements). A derived address obtained from the link state ID. (Note that masking a network links advertisement's link state ID with the network's subnet mask yields the network's IP address.) When the link state advertisement is describing a router, the link state ID is always the described router's OSPF router ID. When an autonomous system external advertisement (LS Type = 5) is describing a default route, its link state ID is set to Default Destination (0.0.0.0).
adv-router [ip-address]	(Optional) Displays all the LSAs of the specified router. If no IP address is included, the information is about the local router itself (in this case, the same as self-originate).
asbr-summary	(Optional) Displays information only about the autonomous system boundary router summary LSAs.
database-summary	(Optional) Displays how many of each type of LSA for each area there are in the database, and the total.
external	(Optional) Displays information only about the external LSAs.
network	(Optional) Displays information only about the network LSAs.
nssa-external	(Optional) Displays information only about the NSSA external LSAs.
router	(Optional) Displays information only about the router LSAs.
self-originate	(Optional) Displays only self-originated LSAs (from the local router).
summary	(Optional) Displays information only about the summary LSAs.

Command Modes

EXEC

Command History

Release	Modification
10.0	This command was introduced.
11.0	The database-summary keyword was added.
12.0	The following keywords were added: self-originate adv-router

Examples

The following is sample output from the show ip ospf database command when no arguments or keywords are used:

Router# show ip ospf database

 
OSPF Router with id(190.20.239.66) (Process ID 300)
 
                 Displaying Router Link States(Area 0.0.0.0)
 
  Link ID       ADV Router      Age        Seq#     Checksum  Link count
155.187.21.6   155.187.21.6    1731    0x80002CFB    0x69BC       8
155.187.21.5   155.187.21.5    1112    0x800009D2    0xA2B8       5
155.187.1.2    155.187.1.2     1662    0x80000A98    0x4CB6       9
155.187.1.1    155.187.1.1     1115    0x800009B6    0x5F2C       1
155.187.1.5    155.187.1.5     1691    0x80002BC     0x2A1A       5
155.187.65.6   155.187.65.6    1395    0x80001947    0xEEE1       4
155.187.241.5  155.187.241.5   1161    0x8000007C    0x7C70       1
155.187.27.6   155.187.27.6    1723    0x80000548    0x8641       4
155.187.70.6   155.187.70.6    1485    0x80000B97    0xEB84       6
 
                Displaying Net Link States(Area 0.0.0.0)
 
  Link ID       ADV Router      Age        Seq#        Checksum
155.187.1.3  192.20.239.66     1245    0x800000EC      0x82E
 
                Displaying Summary Net Link States(Area 0.0.0.0)
 
  Link ID       ADV Router       Age        Seq#        Checksum
155.187.240.0   155.187.241.5    1152      0x80000077      0x7A05
155.187.241.0   155.187.241.5    1152      0x80000070      0xAEB7
155.187.244.0   155.187.241.5    1152      0x80000071      0x95CB
 

The following is sample output from the show ip ospf database command with the asbr-summary keyword:

Router# show ip ospf database asbr-summary

 
OSPF Router with id(190.20.239.66) (Process ID 300)
 
                Displaying Summary ASB Link States(Area 0.0.0.0)
 
	LS age: 1463
	Options: (No TOS-capability)
	LS Type: Summary Links(AS Boundary Router)
	Link State ID: 155.187.245.1 (AS Boundary Router address)
	Advertising Router: 155.187.241.5
	LS Seq Number: 80000072
	Checksum: 0x3548
	Length: 28
	Network Mask: 0.0.0.0 TOS: 0  Metric: 1
 

The following is sample output from the show ip ospf database command with the external keyword:

Router# show ip ospf database external

 
OSPF Router with id(190.20.239.66) (Autonomous system 300)
 
                   Displaying AS External Link States
 
LS age: 280
Options: (No TOS-capability)
LS Type: AS External Link
Link State ID: 143.105.0.0 (External Network Number)
Advertising Router: 155.187.70.6
LS Seq Number: 80000AFD
Checksum: 0xC3A
Length: 36
Network Mask: 255.255.0.0
     		Metric Type: 2 (Larger than any link state path)
     		TOS: 0
     		Metric: 1
     		Forward Address: 0.0.0.0
     		External Route Tag: 0
 

The following is sample output from the show ip ospf database command with the network keyword:

Router# show ip ospf database network

 OSPF Router with id(190.20.239.66) (Process ID 300)
 
                Displaying Net Link States(Area 0.0.0.0)
 
LS age: 1367
Options: (No TOS-capability)
LS Type: Network Links
Link State ID: 155.187.1.3 (address of Designated Router)
Advertising Router: 190.20.239.66
LS Seq Number: 800000E7
Checksum: 0x1229
Length: 52
Network Mask: 255.255.255.0
        Attached Router: 190.20.239.66
        Attached Router: 155.187.241.5
        Attached Router: 155.187.1.1
        Attached Router: 155.187.54.5
        Attached Router: 155.187.1.5
 

The following is sample output from the show ip ospf database command with the router keyword:

Router# show ip ospf database router

 
OSPF Router with id(190.20.239.66) (Process ID 300)
 
 
                Displaying Router Link States(Area 0.0.0.0)
 
LS age: 1176
Options: (No TOS-capability)
LS Type: Router Links
Link State ID: 155.187.21.6
Advertising Router: 155.187.21.6
LS Seq Number: 80002CF6
Checksum: 0x73B7
Length: 120
AS Boundary Router
155   Number of Links: 8
 
Link connected to: another Router (point-to-point)
(link ID) Neighboring Router ID: 155.187.21.5
(Link Data) Router Interface address: 155.187.21.6
Number of TOS metrics: 0
TOS 0 Metrics: 2
 

The following is sample output from show ip ospf database command with the summary keyword:

Router# show ip ospf database summary

 
       OSPF Router with id(190.20.239.66) (Process ID 300)
 
                Displaying Summary Net Link States(Area 0.0.0.0)
 
LS age: 1401
Options: (No TOS-capability)
LS Type: Summary Links(Network)
Link State ID: 155.187.240.0 (summary Network Number)
Advertising Router: 155.187.241.5
LS Seq Number: 80000072
Checksum: 0x84FF
Length: 28
Network Mask: 255.255.255.0   TOS: 0  Metric: 1
 

The following is sample output from show ip ospf database command with the database-summary keyword:

Router# show ip ospf database database-summary

 
          OSPF Router with ID (172.19.65.21) (Process ID 1)
 
Area ID     Router    Network    Sum-Net    Sum-ASBR    Subtotal    Delete    Maxage
202         1         0          0          0           1           0         0
AS External                                             0           0         0
Total       1         0          0          0           1
 

Syntax Description

type	(Optional) Interface type.
number	(Optional) Interface number.

Command Modes

EXEC

Command History

Release	Modification
10.0	This command was introduced.

Examples

The following is sample output of the show ip ospf interface command when Ethernet 0 is specified:

Router# show ip ospf interface ethernet 0

 
Ethernet 0 is up, line protocol is up
Internet Address 131.119.254.202, Mask 255.255.255.0, Area 0.0.0.0
AS 201, Router ID 192.77.99.1, Network Type BROADCAST, Cost: 10
Transmit Delay is 1 sec, State OTHER, Priority 1
Designated Router id 131.119.254.10, Interface address 131.119.254.10
Backup Designated router id 131.119.254.28, Interface addr 131.119.254.28
Timer intervals configured, Hello 10, Dead 60, Wait 40, Retransmit 5
Hello due in 0:00:05
Neighbor Count is 8, Adjacent neighbor count is 2
  Adjacent with neighbor 131.119.254.28  (Backup Designated Router)
  Adjacent with neighbor 131.119.254.10  (Designated Router)
 

Syntax Description

type	(Optional) Interface type.
number	(Optional) Interface number.
neighbor-id	(Optional) Neighbor ID.
detail	(Optional) Displays all neighbors given in detail (list all neighbors).

Command Modes

EXEC

Command History

Release	Modification
10.0	This command was introduced.

Examples

The following is sample output from the show ip ospf neighbor command showing a single line of summary information for each neighbor:

Router# show ip ospf neighbor

 
   ID          Pri   State        Dead Time     Address         Interface
199.199.199.137 1    FULL/DR       0:00:31    160.89.80.37      Ethernet0
192.31.48.1     1    FULL/DROTHER  0:00:33    192.31.48.1       Fddi0
192.31.48.200   1    FULL/DROTHER  0:00:33    192.31.48.200     Fddi0
199.199.199.137 5    FULL/DR       0:00:33    192.31.48.189     Fddi0
 

The following is sample output showing summary information about the neighbor that matches the neighbor ID:

Router# show ip ospf neighbor 199.199.199.137

 
Neighbor 199.199.199.137, interface address 160.89.80.37
    In the area 0.0.0.0 via interface Ethernet0
    Neighbor priority is 1, State is FULL
    Options 2
    Dead timer due in 0:00:32
    Link State retransmission due in 0:00:04
 Neighbor 199.199.199.137, interface address 192.31.48.189
    In the area 0.0.0.0 via interface Fddi0
    Neighbor priority is 5, State is FULL
    Options 2
    Dead timer due in 0:00:32
    Link State retransmission due in 0:00:03
 

If you specify the interface along with the Neighbor ID, the Cisco IOS software displays the neighbors that match the neighbor ID on the interface, as in the following sample display:

Router# show ip ospf neighbor ethernet 0 199.199.199.137

 
Neighbor 199.199.199.137, interface address 160.89.80.37
    In the area 0.0.0.0 via interface Ethernet0
    Neighbor priority is 1, State is FULL
    Options 2
    Dead timer due in 0:00:37
    Link State retransmission due in 0:00:04
 

You can also specify the interface without the neighbor ID to show all neighbors on the specified interface, as in the following sample display:

Router# show ip ospf neighbor fddi 0

 
   ID          Pri   State        Dead Time     Address         Interface
192.31.48.1     1    FULL/DROTHER  0:00:33    192.31.48.1       Fddi0
192.31.48.200   1    FULL/DROTHER  0:00:32    192.31.48.200     Fddi0
199.199.199.137 5    FULL/DR       0:00:32    192.31.48.189     Fddi0
 

The following is sample output from the show ip ospf neighbor detail command:

Router# show ip ospf neighbor detail

 
Neighbor 160.89.96.54, interface address 160.89.96.54
    In the area 0.0.0.3 via interface Ethernet0
    Neighbor priority is 1, State is FULL
    Options 2
    Dead timer due in 0:00:38
 Neighbor 160.89.103.52, interface address 160.89.103.52
    In the area 0.0.0.0 via interface Serial0
    Neighbor priority is 1, State is FULL
    Options 2
    Dead timer due in 0:00:31
 

Syntax Description

nbr	(Optional) Neighbor. Displays the list of all LSAs requested by the router from this neighbor.
intf	(Optional) Interface. Displays the list of all LSAs requested by the router from this interface.
intf-nbr	(Optional) Displays the list of all LSAs requested by the router on this interface from this neighbor.

Command Modes

EXEC

Command History

Release	Modification
10.2	This command was introduced.

Usage Guidelines

The information displayed by the show ip ospf request-list command is useful in debugging OSPF routing operations.

Examples

The following is sample output from the show ip ospf request-list command:

router# show ip ospf request-list se0

 
             OSPF Router with ID (200.1.1.11) (Process ID 1)
 
  Neighbor 200.1.1.12, interface Serial0 address 144.1.1.12
 
  Type  LS ID           ADV RTR         Seq NO      Age    Checksum
     1  200.1.1.12      200.1.1.12      0x8000020D  8      0x6572
 
 

Syntax Description

nbr	(Optional) Neighbor. Displays the list of all LSAs waiting to be retransmitted for this neighbor.
intf	(Optional) Interface. Displays the list of all LSAs waiting to be retransmitted on this interface.
intf-nbr	(Optional) Displays the list of all LSAs waiting to be retransmitted on this interface, from this neighbor.

Command Modes

EXEC

Command History

Release	Modification
10.2	This command was introduced.

Usage Guidelines

The information displayed by the show ip ospf retransmission-list command is useful in debugging OSPF routing operations.

Examples

The following is sample output from the show ip ospf retransmission-list command:

Router# show ip ospf retransmission-list se0

 
             OSPF Router with ID (200.1.1.12) (Process ID 1)
 
  Neighbor 200.1.1.11, interface Serial0 address 144.1.1.11
  Link state retransmission due in 3764 msec, Queue length 2
 
  Type  LS ID           ADV RTR         Seq NO      Age    Checksum
     1  200.1.1.12      200.1.1.12      0x80000210  0      0xB196

Syntax Description

process-id

(Optional) OSPF area ID.

Command Modes

EXEC

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

The process-id can be entered as a decimal number or as an IP address format.

Examples

The following is sample output from the show ip ospf summary-address command:

Router# show ip ospf summary-address

 
 OSPF Process 2, Summary-address
 
 1.2.0.0/255.255.0.0 Metric -1, Type 0, Tag 0
 1.2.0.0/255.255.0.0 Metric -1, Type 0, Tag 10
 

Syntax Description

This command has no arguments or keywords.

Command Modes

EXEC

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

The information displayed by the show ip ospf virtual-links command is useful in debugging OSPF routing operations.

Examples

The following is sample output from the show ip ospf virtual-links command:

Router# show ip ospf virtual-links

 
Virtual Link to router 160.89.101.2 is up
Transit area 0.0.0.1, via interface Ethernet0, Cost of using 10
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 0:00:08
Adjacency State FULL
 

Syntax Description

address	Summary address designated for a range of addresses.
mask	IP subnet mask used for the summary route.
level-1	Only routes redistributed into Level 1 are summarized with the configured address/mask value. This keyword applies to IS-IS only.
level-1-2	The summary router is injected into both a Level 1 area and a Level 2 subdomain. This keyword applies to IS-IS only.
level-2	Routes learned by Level 1 routing will be summarized into the Level 2 backbone with the configured address/mask value. This keyword applies to IS-IS only.
prefix	IP route prefix for the destination.
mask	IP subnet mask used for the summary route.
not-advertise	(Optional) Used to suppress routes that match the prefix/mask pair. This keyword applies to OSPF only.
tag tag	(Optional) Tag value that can be used as a "match" value for controlling redistribution via route maps. This keyword applies to OSPF only.

Defaults

Disabled

Command Modes

Router configuration

Command History

Release	Modification
10.0	This command was introduced.

Usage Guidelines

Using this command for OSPF causes an OSPF autonomous system boundary router (ASBR) to advertise one external route as an aggregate for all redistributed routes that are covered by the address. For OSPF, this command summarizes only routes from other routing protocols that are being redistributed into OSPF. Use the area range command for route summarization between OSPF areas.

Examples

In the following example, summary address 10.1.0.0 includes address 10.1.1.0, 10.1.2.0, 10.1.3.0, and so forth. Only the address 10.1.0.0 is advertised in an external link state advertisement.

summary-address 10.1.0.0 255.255.0.0

Related Commands

Command	Description
area range	Consolidates and summarizes routes at an area boundary.
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.

Syntax Description

seconds

Number of seconds in the interval at which LSAs are grouped and refreshed, checksummed, or aged. The range is 10 seconds to 1800 seconds. The default value is 240 seconds.

Defaults

240 seconds

Command Modes

Router configuration

Command History

Release	Modification
11.3 AA	This command was introduced.

Usage Guidelines

OSPF LSA group pacing is enabled by default. For typical customers, the default group pacing interval for refreshing, checksumming, and aging is appropriate and you need not configure this feature.

The duration of the LSA group pacing is inversely proportional to the number of LSAs the router is handling. For example, if you have approximately 10,000 LSAs, decreasing the pacing interval would benefit you. If you have a very small database (40 to 100 LSAs), increasing the pacing interval to 10 to 20 minutes might benefit you slightly.

Examples

The following example changes the OSPF pacing between LSA groups to 60 seconds:

router ospf
 timers lsa-group-pacing 60

Syntax Description

spf-delay	Delay time, in seconds, between when OSPF receives a topology change and when it starts a SPF. calculation. It can be an integer from 0 to 65535. The default time is 5 seconds. A value of 0 means that there is no delay; that is, the SPF calculation is started immediately.
spf-holdtime	Minimum time, in seconds, between two consecutive SPF calculations. It can be an integer from 0 to 65535. The default time is 10 seconds. A value of 0 means that there is no delay; that is, two consecutive SPF calculations can be done one immediately after the other.

Defaults

spf-delay: 5 seconds

spf-holdtime: 10 seconds

Command Modes

Router configuration

Command History

Release	Modification
10.3	This command was introduced.

Usage Guidelines

Setting the delay and hold time low causes routing to switch to the alternate path more quickly in the event of a failure. However, it consumes more CPU processing time.

Examples

The following example changes the delay to 10 seconds and the hold time to 20 seconds:

timers spf 10 20