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default-information originate (OSPF)
ip ospf database-filter all out
OSPF Commands
area authentication
To enable authentication for an Open Shortest Path First (OSPF) area, use the area authentication command in router configuration mode. To remove an authentication specification of an area or a specified area from the configuration, use the no form of this command.
area area-id authentication [message-digest]
no area area-id authentication [message-digest]
Syntax Description
Defaults
Type 0 authentication (no authentication)
Command Modes
Router configuration
Command History
Usage Guidelines
Specifying authentication for an area sets the authentication to Type 1 (simple password) as specified in RFC 1247. If this command is not included in the configuration file, authentication of Type 0 (no authentication) is assumed.
The authentication type must be the same for all routers and access servers in an area. The authentication password for all OSPF routers on a network must be the same if they are to communicate with each other via OSPF. Use the ip ospf authentication-key interface command to specify this password.
If you enable MD5 authentication with the message-digest keyword, you must configure a password with the ip ospf message-digest-key interface command.
To remove the authentication specification for an area, use the no form of this command with the authentication keyword.
Note
To remove the specified area from the software configuration, use the no area area-id command (with no other keywords). That is, the no area area-id command removes all area options, such as area authentication, area default-cost, area nssa, area range, area stub, and area virtual-link.
Examples
The following example mandates authentication for areas 0 and 10.0.0.0 of OSPF routing process 201. Authentication keys are also provided.
interface ethernet 0ip address 192.168.251.201 255.255.255.0ip ospf authentication-key adcdefgh!interface ethernet 1ip address 10.56.0.201 255.255.0.0ip ospf authentication-key ijklmnop!router ospf 201network 10.0.0.0 0.255.255.255 area 10.0.0.0network 192.168.0.0 0.0.255.255 area 0area 10.0.0.0 authenticationarea 0 authenticationRelated Commands
area default-cost
To specify a cost for the default summary route that is sent into a stub area or not-so-stubby area (NSSA), use the area default-cost command in router address family topology or router configuration mode. To remove the assigned default route cost, use the no form of this command.
area area-id default-cost cost
no area area-id default-cost cost
Syntax Description
Command Default
cost: 1
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
This command is used only on an Area Border Router (ABR) attached to a stub area or NSSA.
There are two stub area router configuration commands: the stub and default-cost options of the area command. In all routers and access servers attached to the stub area, the area should be configured as a stub area using the stub option of the area command. Use the default-cost option only on an ABR attached to the stub area. The default-cost option provides the metric for the summary default route generated by the ABR into the stub area.
Note
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the area default-cost command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example assigns a default cost of 20 to stub network 10.0.0.0:
interface ethernet 0ip address 10.56.0.201 255.255.0.0!router ospf 201network 10.0.0.0 0.255.255.255 area 10.0.0.0area 10.0.0.0 stubarea 10.0.0.0 default-cost 20Related Commands
area authentication
Enables authentication for an OSPF area.
area stub
Defines an area as a stub area.
area filter-list
To filter prefixes advertised in type 3 link-state advertisements (LSAs) between Open Shortest Path First (OSPF) areas of an Area Border Router (ABR), use the area filter-list command in router address family topology or router configuration mode. To change or cancel the filter, use the no form of this command.
area area-id filter-list prefix prefix-list-name {in | out}
no area area-id filter-list prefix prefix-list-name {in | out}
Syntax Description
Command Default
This command is disabled by default. The router will not filter prefixes.
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
With this feature enabled in the "in" direction, all type 3 LSAs originated by the ABR to this area, based on information from all other areas, are filtered by the prefix list. Type 3 LSAs that were originated as a result of the area range command in another area are treated like any other type 3 LSA that was originated individually. Any prefix that does not match an entry in the prefix list is implicitly denied.
With this feature enabled in the "out" direction, all type 3 LSAs advertised by the ABR, based on information from this area to all other areas, are filtered by the prefix list. If the area range command has been configured for this area, type 3 LSAs that correspond to the area range are sent to all other areas, only if at least one prefix in the area range matches an entry in the prefix list.
If all specific prefixes are denied by the prefix list, type 3 LSAs that correspond to the area range command will not be sent to any other area. Prefixes that are not permitted by the prefix list are implicitly denied.
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the area filter-list command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example filters prefixes that are sent from all other areas to area 1:
area 1 filter-list prefix AREA_1 inRelated Commands
area nssa
To configure a not-so-stubby area (NSSA), use the area nssa command in router address family topology or router configuration mode. To remove the NSSA distinction from the area, use the no form of this command.
area area-id nssa [no-redistribution] [default-information-originate [metric] [metric-type]] [no-summary] [nssa-only]
no area area-id nssa [no-redistribution] [default-information-originate [metric] [metric-type]] [no-summary] [nssa-only]
Syntax Description
Command Default
No NSSA area is defined.
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
To remove the specified area from the software configuration, use the no area area-id command (with no other keywords). That is, the no area area-id command removes all area options, including area authentication, area default-cost, area nssa, area range, area stub, and area virtual-link.
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the area nssa command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example makes area 1 an NSSA area:
router ospf 1redistribute rip subnetsnetwork 172.19.92.0 0.0.0.255 area 1area 1 nssaRelated Commands
redistribute
Redistributes routes from one routing domain into another routing domain.
area nssa translate
To configure a not-so-stubby area (NSSA) and to configure the OSPF Forwarding Address Suppression in Translated Type-5 LSAs feature, use the area nssa translate command in router address family topology or router configuration mode. To remove the NSSA distinction from the area, use the no form of this command.
area area-id nssa translate type7 {[always] [suppress-fa]} [default-information-originate [metric ospf-metric] [metric-type ospf-link-state-type] [nssa-only]] [no-ext-capability] [no-redistribution] [no-summary]
no area area-id nssa translate type7 {[always] [suppress-fa]} [default-information-originate [metric ospf-metric] [metric-type ospf-link-state-type] [nssa-only]] [no-ext-capability] [no-redistribution] [no-summary]
Syntax Description
Command Default
The ABRs connecting an NSSA and the backbone areas elect one of them to translate LSAs, which means that a router might be elected as translator.
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)
Usage Guidelines
To configure the OSPF Forwarding Address Suppression in Translated Type-5 LSAs feature, configure the translate type7 suppress-fa keywords. Consider the following caution.
Caution
If the the no-redistribution or default-information-originate keywords are used, two separate lines for the area nssa command appear in the configuration file for ease of readability. For example, if the area 6 nssa translate type7 suppress-fa no-redistribution command is configured, the following lines would appear in the configuration file:
router ospf 1area 6 nssa no-redistributionarea 6 nssa translate type7 suppress-faCisco IOS Release 15.1(2)S and later releases support RFC 3101 and include the always keyword, which allows you to configure an NSSA ABR router as a forced NSSA LSA translator. This means that the NSSA ABR router will unconditionally assume the role of LSA translator, preempting the default behavior, which would only include it among the candidates to be elected as translator.
Note
You can configure the always keyword only in router configuration mode, not in router address family topology configuration mode.
To remove the specified area from the software configuration, use the no area area-id command (with no other keywords). That is, the no area area-id command removes all area options, such as area authentication, area default-cost, area nssa, area range, area stub, and area virtual-link.
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature with this command, you you must do so in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example causes OSPF to translate Type-7 LSAs from area 1 to Type-5 LSAs, but not place the Type-7 forwarding address into the Type-5 LSAs. OSPF places 0.0.0.0 as the forwarding address in the Type-5 LSAs.
router ospf 2network 172.19.92.0 0.0.0.255 area 1area 1 nssa translate type7 suppress-faThe following example configures an NSSA ABR as a forced LSA translator.
Router(config-router)# area 10 nssa translate type7 alwaysRelated Commands
redistribute
Redistributes routes from one routing domain into another routing domain.
area range
To consolidate and summarize routes at an area boundary, use the area range command in router address family topology or router configuration mode. To disable this function, use the no form of this command.
area area-id range ip-address ip-address-mask [advertise | not-advertise] [cost cost]
no area area-id range ip-address ip-address-mask [advertise | not-advertise] [cost cost]
Syntax Description
Command Default
This command is disabled by default.
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
The area range command is used only with Area Border Routers (ABRs). It is used to consolidate or summarize routes for an area. The result is that a single summary route is advertised to other areas by the ABR. Routing information is condensed at area boundaries. External to the area, a single route is advertised for each address range. This behavior is called route summarization.
Multiple area range router configuration commands can be configured. Thus, OSPF can summarize addresses for many different sets of address ranges.
Note
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the area range command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example specifies one summary route to be advertised by the ABR to other areas for all subnets on network 10.0.0.0 and for all hosts on network 192.168.110.0:
interface ethernet 0ip address 192.168.110.201 255.255.255.0!interface ethernet 1ip address 192.168.120.201 255.255.255.0!router ospf 201network 192.168.110.0 0.0.0.255 area 0area 10.0.0.0 range 10.0.0.0 255.0.0.0area 0 range 192.168.110.0 255.255.0.0Related Commands
area range (IPv6)
Consolidates and summarizes routes at an area boundary in an IPv6 network.
area sham-link
To configure a sham-link interface on a provider edge (PE) router in a Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) backbone, use the area sham-link command in router configuration mode. To remove the sham-link, use the no form of this command.
area area-id sham-link source-address destination-address [cost number] [ttl-security
hops hop-count]no area area-id sham-link source-address destination-address
Syntax Description
Command Default
No default behavior or values
Command Modes
Router configuration (config-router)
Command History
Usage Guidelines
In the MPLS VPN environment, several VPN client sites can be connected in the same OSPF area. If these sites are connected over a backdoor link in addition to the VPN backbone, all traffic passes over the backdoor link instead of over the VPN backbone. OSPF always selects intra-area routes over interarea (external) routes.
To correct this default OSPF behavior in an MPLS VPN, use the area sham-link command to configure a sham link between two PEs to connect the sites through the MPLS VPN backbone. A sham link represents an intra-area (unnumbered point-to-point) connection between PEs. All other routers in the area use the sham link to calculate intra-area shortest path first (SPF) routes to the remote site.
Configure the source and destination addresses of the sham link as a host route mask (255.255.255.255) on the PE routers that serve as the endpoints of the sham link. The source and destination IP addresses must belong to the VPN routing and forwarding instance (VRF) and be advertised by Border Gateway Protocol (BGP) to remote PE routers. The sham link endpoint addresses should not be advertised by OSPF.
Use the ttl-security hops hop-count keywords and argument to enable checking of TTL values on OSPF packets from neighbors or set TTL values sent to neighbors. This feature adds an extra layer of protection to OSPF.
Examples
The following example shows how to configure a sham link between two PE routers in an MPLS VPN backbone by using the area sham-link command on each router:
Router1(config)# interface loopback 55Router1(config-if)# ip vrf forwarding v1Router1(config-if)# ip address 10.0.0.1 255.255.255.255!Router1(config)# router ospf 2 vrf v1Router1(config-router)# log-adjacency-changesRouter1(config-router)# area 120 sham-link 10.0.0.1 172.16.0.1 cost 1Router1(config-router)# redistribute bgp 1 subnetsRouter1(config-router)# network 10.2.0.1 255.255.255.255 area 1Router1(config-router)# network 10.120.0.0 0.255.255.255 area 120Router1(config-router)# network 10.140.0.0 0.255.255.255 area 120!Router2(config)# interface loopback 44Router2(config-if)# ip vrf forwarding v1Router2(config-if)# ip address 172.16.0.1 255.255.255.255!Router2(config)# router ospf 2 vrf v1Router2(config-router)# log-adjacency-changesRouter2(config-router)# area 120 sham-link 172.16.0.1 10.0.0.1 cost 1Router2(config-router)# redistribute bgp 1 subnetsRouter2(config-router)# network 10.2.0.1 255.255.255.255 area 1Router2(config-router)# network 10.120.0.0 0.255.255.255 area 120Router2(config-router)# network 10.140.0.0 0.255.255.255 area 120!Related Commands
ttl-security hops
Enables checking of TTL values on OSPF packets from neighbors or setting TTL values sent to neighbors.
area stub
To define an area as a stub area, use the area stub command in router address family topology or router configuration mode. To disable this function, use the no form of this command.
area area-id stub [no-summary]
no area area-id stub [no-summary]
Syntax Description
area-id
Identifier for the stub area; either a decimal value or an IP address.
no-summary
(Optional) Prevents an Area Border Router (ABR) from sending summary link advertisements into the stub area.
Defaults
No stub area is defined.
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
You must configure the area stub command on all routers and access servers in the stub area. Use the area router configuration command with the default-cost keyword to specify the cost of a default internal route sent into a stub area by an ABR.
There are two stub area router configuration commands: the stub and default-cost options of the area router configuration command. In all routers attached to the stub area, the area should be configured as a stub area using the stub keyword of the area command. Use the default-cost keyword only on an ABR attached to the stub area. The default-cost keyword provides the metric for the summary default route generated by the ABR into the stub area.
To further reduce the number of link-state advertisements (LSAs) sent into a stub area, you can configure the no-summary keyword on the ABR to prevent it from sending summary LSAs (LSA type 3) into the stub area.
Note
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the area stub command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example assigns a default cost of 20 to stub network 10.0.0.0:
interface ethernet 0ip address 10.56.0.201 255.255.0.0!router ospf 201network 10.0.0.0 0.255.255.255 area 10.0.0.0area 10.0.0.0 stubarea 10.0.0.0 default-cost 20Related Commands
area authentication
Enables authentication for an OSPF area.
area default-cost
Specifies a cost for the default summary route sent into a stub area.
area virtual-link
To define an Open Shortest Path First (OSPF) virtual link, use the area virtual-link command in router address family topology or router configuration mode. To remove a virtual link, use the no form of this command.
area area-id virtual-link router-id [hello-interval seconds] [retransmit-interval seconds] [transmit-delay seconds] [dead-interval seconds] [ttl-security hops hop-count]
no area area-id virtual-link router-id
Syntax Description
Command Default
No OSPF virtual link is defined.
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
In OSPF, all areas must be connected to a backbone area. If the connection to the backbone is lost, it can be repaired by establishing a virtual link.
The smaller the hello interval, the faster topological changes will be detected, but more routing traffic will ensue. The setting of the retransmit interval should be conservative, or needless retransmissions will result. The value should be larger for serial lines and virtual links.
The transmit delay value should take into account the transmission and propagation delays for the interface.
To configure a virtual link in OSPF for IPv6, you must use a router ID instead of an address. In OSPF for IPv6, the virtual link takes the router ID rather than the IPv6 prefix of the remote router.
Use the ttl-security hops hop-count keywords and argument to enable checking of TTL values on OSPF packets from neighbors or to set TTL values sent to neighbors. This feature adds an extra layer of protection to OSPF.
Note
Note
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the area virtual-link command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example establishes a virtual link with default values for all optional parameters:
ipv6 router ospf 1log-adjacency-changesarea 1 virtual-link 192.168.255.1The following example establishes a virtual link in OSPF for IPv6:
ipv6 router ospf 1log-adjacency-changesarea 1 virtual-link 192.168.255.1 hello-interval 5Related Commands
auto-cost
To control how Open Shortest Path First (OSPF) calculates default metrics for the interface, use the auto-cost command in router configuration mode. To assign cost based only on the interface type, use the no form of this command.
auto-cost reference-bandwidth mbps
no auto-cost reference-bandwidth
Syntax Description
reference-bandwidth mbps
Rate in Mbps (bandwidth). The range is from 1 to 4294967; the default is 100.
Defaults
100 Mbps
Command Modes
Router configuration
Command History
Usage Guidelines
In Cisco IOS Release 10.3 and later releases, by default OSPF will calculate the OSPF metric for an interface according to the bandwidth of the interface. For example, a 64K link will get a metric of 1562, and a T1 link will have a metric of 64.
The OSPF metric is calculated as the ref-bw value divided by the bandwidth, with mbps equal to 108 by default, and bandwidth determined by the bandwidth (interface) command. The calculation gives FDDI a metric of 1.
If you have multiple links with high bandwidth (such as FDDI or ATM), you might want to use a larger number to differentiate the cost on those links.
The value set by the ip ospf cost command overrides the cost resulting from the auto-cost command.
Examples
The following example changes the cost of the FDDI link to 10, while the gigabit Ethernet link remains at a cost of 1. Thus, the link costs are differentiated.
router ospf 1auto-cost reference-bandwidth 1000Related Commands
capability lls
To enable the use of the Link-Local Signalling (LLS) data block in originated Open Shortest Path First (OSPF) packets and reenable OSPF nonstop forwarding (NSF) awareness, use the capability lls command in router configuration mode. To disable LLS and OSPF NSF awareness, use the no form of this command.
capability lls
no capability lls
Syntax Description
This command has no arguments or keywords.
Command Default
LLS is enabled.
Command Modes
Router configuration
Command History
Usage Guidelines
You might want to disable NSF awareness by disabling the use of the LLS data block in originated OSPF packets. You might want to disable NSF awareness if the router has no applications using LLS.
If NSF is configured and you try to disable LLS, you will receive the error message, "OSPF Non-Stop Forwarding (NSF) must be disabled first."
If LLS is disabled and you try to configure NSF, you will receive the error message, "OSPF Link-Local Signaling (LLS) capability must be enabled first."
Examples
The following example disables LLS support and OSPF NSF awareness:
router ospf 2no capability llscapability transit
To reenable Open Shortest Path First (OSPF) area capability transit after it has been disabled, use the capability transit command in router configuration mode. To disable OSPF area capability transit on all areas for a router process, use the no form of this command.
capability transit
no capability transit
Syntax Description
This command has no arguments or keywords.
Defaults
OSPF area capability transit is enabled.
Command Modes
Router configuration
Command History
Usage Guidelines
OSPF area capability transit is enabled by default, allowing the OSPF Area Border Router to install better-cost routes to the backbone area through the transit area instead of the virtual links. If you want to retain a traffic pattern through the virtual-link path, you can disable capability transit by entering the no capability transit command. If paths through the transit area are discovered, they are most likely to be more optimal paths, or at least equal to, the virtual-link path. To reenable capability transit, enter the capability transit command.
If you need to verify whether OSPF area capability transit is enabled for a specific routing process, enter the show ip ospf command.
Examples
The following example shows how to disable OSPF area capability transit on all areas for a router process named ospf 1. A show ip ospf command is issued first to display the current areas that have area capability transit enabled. The no capability transit command is then entered to disable OSPF area capability transit on all areas for the router process ospf 1.
Router# show ip ospfRouting Process "ospf 1" with ID 10.1.1.1Supports only single TOS(TOS0) routesSupports opaque LSASupports Link-local Signaling (LLS)!Supports area transit capabilityIt is an area border routerInitial SPF schedule delay 5000 msecsMinimum hold time between two consecutive SPFs 10000 msecsMaximum wait time between two consecutive SPFs 10000 msecsMinimum LSA interval 5 secs. Minimum LSA arrival 1 secsLSA group pacing timer 240 secsInterface flood pacing timer 33 msecsRetransmission pacing timer 66 msecsNumber of external LSA 8. Checksum Sum 0x02853FNumber of opaque AS LSA 0. Checksum Sum 0x000000Number of DCbitless external and opaque AS LSA 0Number of DoNotAge external and opaque AS LSA 0Number of areas in this router is 2. 2 normal 0 stub 0 nssa!Number of areas transit capable is 1External flood list length 0Area BACKBONE(0)Number of interfaces in this area is 3Area has no authenticationSPF algorithm last executed 00:02:21.524 agoSPF algorithm executed 11 timesArea ranges areNumber of LSA 49. Checksum Sum 0x19B5FANumber of opaque link LSA 0. Checksum Sum 0x000000Number of DCbitless LSA 0Number of indication LSA 0Number of DoNotAge LSA 38Flood list length 0Area 1Number of interfaces in this area is 3!This area has transit capability: Virtual Link EndpointArea has no authenticationSPF algorithm last executed 00:02:36.544 agoSPF algorithm executed 9 timesArea ranges areNumber of LSA 42. Checksum Sum 0x1756D5Number of opaque link LSA 0. Checksum Sum 0x000000Number of DCbitless LSA 0Number of indication LSA 0Number of DoNotAge LSA 0Flood list length 0Router(config)# router ospf 1Router(router-config)# no capability transit
Related Commands
capability vrf-lite
To suppress the provider edge (PE) specific checks on a router when the Open Shortest Path First (OSPF) process is associated with the VPN routing and forwarding instance (VRF), use the capability vrf-lite command in router configuration mode. To restore the checks, use the no form of this command.
capability vrf-lite
no capability vrf-lite
Syntax Description
This command has no arguments or keywords.
Defaults
Disabled. PE specific checks are performed if the process is associated with VRF command modes.
Command Modes
Router configuration
Command History
Usage Guidelines
This command works only if the OSPF process is associated with the VRF.
When the OSPF process is associated with the VRF, several checks are performed when link-state advertisements (LSAs) are received. PE checks are needed to prevent loops when the PE is performing a mutual redistribution between OSPF and Border Gateway Protocol (BGP) interfaces.
Table 1 describes the PE checks performed when Type-3, Type-5, and Type-7 LSAs are received.
In some situations, performing PE checks might not be desirable. The concept of VRFs can be used on a router that is not a PE router (that is, a router that is not running BGP). With the capability vrf-lite command, the checks can be turned off to allow correct population of the VRF routing table with routes to IP prefixes.
Examples
This example shows a router configured with multi-VRF:
router ospf 100 vrf grccapability vrf-liteclear ip ospf
To clear redistribution based on the Open Shortest Path First (OSPF) routing process ID, use the clear ip ospf command in privileged EXEC mode.
clear ip ospf [pid] {process | redistribution | counters [neighbor [neighbor-interface] [neighbor-id]]}
Syntax Description
Command Modes
Privileged EXEC
Command History
Usage Guidelines
Use the pid argument to clear only one OSPF process. If the pid argument is not specified, all OSPF processes are cleared.
Prior to Cisco IOS Release 12.2(33)SXH, when the clear ip ospf process command is executed, even if a local address is no longer available, the default router ID remains the same. In Cisco IOS Release 12.2(33)SXH, that behavior changed so that when the clear ip ospf process command is executed OSPF checks if the currently in-use router ID is still available as a local address. If it is not, OSPF runs a re-election and changes its router ID.
Examples
The following example shows how to clear all OSPF processes:
Router# clear ip ospf processclear ip ospf force-spf
To start the shortest path first (SPF) algorithm without clearing the Open Shortest Path First (OSPF) database, use the clear ip ospf force-spf command in privileged EXEC mode.
clear ip ospf [process-id] force-spf
Syntax Description
Command Modes
Privileged EXEC (#)
Command History
Usage Guidelines
The clear ip ospf force-spf command is used in troubleshooting and for testing purposes. This command is used to verify if the currently computed routes are correct, to generate debug messages, and so on.
Examples
The following example shows how to start the SPF algorithm without first clearing the OSPF database:
Router# clear ip ospf 1000 force-spfRelated Commands
clear ip ospf redistribution
Clears redistribution based on the OSPF routing process ID.
clear ip ospf traffic
To clear Open Shortest Path First (OSPF) traffic statistics, use the clear ip ospf traffic command in user EXEC or privileged EXEC mode.
clear ip ospf [process-id] traffic [interface-type interface-number]
Syntax Description
Command Modes
User EXEC
Privileged EXECCommand History
12.3(11)T
This command was introduced.
12.0(28)S
This command was integrated into Cisco IOS Release 12.0(28)S.
Examples
The following example clears OSPF traffic statistics for the OSPF process 100:
Router# clear ip ospf 100 trafficRelated Commands
clear ipv6 ospf traffic
To reset counters and clear IPv6 OSPFv3 traffic statistics, use the clear ipv6 ospf traffic command privileged EXEC mode.
clear ipv6 ospf traffic
Syntax Description
This command has no arguments or keywords.
Command Modes
Privileged EXEC
Command History
Examples
The following example resets the counters and clears the OSPFv3 traffics statistics:
Router# clear ipv6 ospf trafficRelated Commands
clear ip ospf traffic
Clears OSPFv2 traffic statistics.
show ip ospf traffic
Displays OSPFv2 traffic statistics.
show ipv6 ospf traffic
Displays OSPFv3 traffic statistics.
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
Usage Guidelines
This command is backward compatible with Cisco IOS Release 12.0.
To minimize the chance of routing loops, all Open Shortest Path First (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 1compatible rfc1583!compatible rfc1587
To replace RFC 3101 compatibility with RFC 1587 compatibility for route selection in not-so-stubby area (NSSA) Area Border Routers (ABRs), use the compatible rfc1587 command in router configuration mode. To restore RFC 3101 compatibility, use the no form of this command.
compatible rfc1587
no compatible rfc1587
Syntax Description
This command has no arguments or keywords.
Command Default
Route selection is compatible with RFC 3101.
Command Modes
Router configuration (config-router)
Command History
Usage Guidelines
In Cisco IOS Release 15.1(2)S and later releases, RFC 3101 replaces RFC 1587, and RFC 3101 behavior is automatically enabled. You can choose the route selection behavior by configuring a router to run as RFC 3101 or RFC 1587 compatible.
Examples
The following example specifies that the router process is compatible with RFC 1587:
Router> enableRouter# configure terminalRouter(config)# router ospf 1Router(config-router)# compatible rfc1587default-information originate (OSPF)
To generate a default external route into an Open Shortest Path First (OSPF) routing domain, use the default-information originate command in router configuration or router address family topology 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
Command Default
This command is disabled by default. No default external route is generated into the OSPF routing domain.
Command Modes
Router configuration (config-router)
Router address family topology configuration (config-router-af-topology)Command History
Usage Guidelines
Whenever you use the redistribute or the default-information router configuration command to redistribute routes into an OSPF routing domain, the Cisco IOS software automatically becomes an Autonomous System Boundary Router (ASBR). However, an ASBR does not, by default, generate a default route into the OSPF routing domain. The software still must have a default route for itself before it generates one, except when you have specified the always keyword.
When a route map is used, the origination of the default route by OSPF is not bound to the existence of a default route in the routing table.
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the default-information originate command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example specifies a metric of 100 for the default route that is redistributed into the OSPF routing domain and an external metric type of Type 1:
router ospf 109redistribute eigrp 108 metric 100 subnetsdefault-information originate metric 100 metric-type 1Related Commands
default-metric (OSPF)
To set default metric values for the Open Shortest Path First (OSPF) routing protocol, use the default-metric command in router address family topology or router configuration mode. To return to the default state, use the no form of this command.
default-metric metric-value
no default-metric metric-value
Syntax Description
Defaults
Built-in, automatic metric translations, as appropriate for each routing protocol. The metric of redistributed connected and static routes is set to 0.
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
The default-metric command is used in conjunction with the redistribute router configuration command to cause the current routing protocol to use the same metric value for all redistributed routes. A default metric helps solve the problem of redistributing routes with incompatible metrics. Whenever metrics do not convert, using a default metric provides a reasonable substitute and enables the redistribution to proceed.
Note
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the default-metric command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example shows a router in autonomous system 109 using both the Routing Information Protocol (RIP) and the OSPF routing protocols. The example advertises OSPF-derived routes using RIP and assigns the Internal Gateway Protocol (IGP)-derived routes a RIP metric of 10.
router ripdefault-metric 10redistribute ospf 109Related Commands
redistribute (IP)
Redistributes routes from one routing domain into another routing domain.
discard-route
To reinstall an external or internal discard route that was previously removed, use the discard-route command in router address family topology configuration or router configuration mode. To remove an external or internal discard route, use the no form of this command.
discard-route [external [distance]] [internal [distance]]
no discard-route [external [distance]] [internal [distance]]
Syntax Description
Defaults
External and internal discard-route entries are installed.
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
External and internal discard-route entries are installed in routing tables by default. During route summarization, routing loops may occur when data is sent to a nonexisting network that appears to be a part of the summary, and the router that is performing the summarization has a less specific route (pointing back to the sending router) for this network in its routing table. To prevent the routing loop, a discard route entry is installed in the routing table of the ABR or ASBR.
If for any reason you do not want to use the external or internal discard route, remove the discard route by entering the no discard-route command with the external or internal keyword.
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the discard-route command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Release 12.4(15)T
Prior to Cisco IOS Release 12.4(15)T, both external and internal discard routes were installed using the default OSPF intra-area administrative distance 110. You can now modify this default distance for discard routes by entering a new administrative distance for the distance argument of the discard-route command.
Examples
The following display shows the discard-route functionality installed by default. When external or internal routes are summarized, a summary route to Null0 will appear in the router output from the show ip route command. See the router output that refers to Null0:
Router# show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGPD - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter areaN1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGPi - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2ia - IS-IS inter area, * - candidate default, U - per-user static routeo - ODR, P - periodic downloaded static routeGateway of last resort is not set172.16.0.0/24 is variably subnetted, 3 subnets, 2 masksC 172.16.0.128/25 is directly connected, Loopback1O 172.16.0.0/24 is a summary, 00:00:14, Null0C 172.16.0.0/25 is directly connected, Loopback0172.31.0.0/24 is variably subnetted, 3 subnets, 2 masksC 172.31.0.128/25 is directly connected, Loopback3O 172.31.0.0/24 is a summary, 00:00:02, Null0C 172.31.0.0/25 is directly connected, Loopback2C 192.168.0.0/24 is directly connected, Ethernet0/0Router# show ip route ospf172.16.0.0/24 is variably subnetted, 3 subnets, 2 masksO 172.16.0.0/24 is a summary, 00:00:29, Null0172.16.0.0/24 is variably subnetted, 3 subnets, 2 masksO 172.16.0.0/24 is a summary, 00:00:17, Null0When the no discard-route command with the internal keyword is entered, notice the following route change, indicated by the router output that refers to Null0:
Router# configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)# router ospf 1Router(config-router)# no discard-route internalRouter(config-router)# endRouter# show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGPD - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter areaN1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGPi - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2ia - IS-IS inter area, * - candidate default, U - per-user static routeo - ODR, P - periodic downloaded static routeGateway of last resort is not set172.16.0.0/24 is variably subnetted, 3 subnets, 2 masksC 172.16.0.128/25 is directly connected, Loopback1C 172.16.0.0/25 is directly connected, Loopback0172.31.0.0/24 is variably subnetted, 3 subnets, 2 masksC 172.31.0.128/25 is directly connected, Loopback3O 172.31.0.0/24 is a summary, 00:00:02, Null0C 172.31.0.0/25 is directly connected, Loopback2C 192.168.0.0/24 is directly connected, Ethernet0/0Router# show ip route ospf172.31.0.0/24 is variably subnetted, 3 subnets, 2 masksO 172.16.0.0/24 is a summary, 00:04:14, Null0Next, the no discard-route command with the external keyword is entered to remove the external discard route entry:
Router# configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)# router ospf 1Router(config-router)# no discard-route externalRouter(config-router)# endThe following router output from the show running-config command confirms that both the external and internal discard routes have been removed from the routing table of the router. See the router output that refers to discard routes.
Router# show running-configBuilding configuration...Current configuration : 1114 bytes!version 12.2service timestamps debug uptimeservice timestamps log uptimeno service password-encryption!hostname Router...router ospf 1log-adjacency-changesno discard-route externalno discard-route internalarea 1 range 172.16.0.0 255.255.255.0summary-address 172.31.0.0 255.255.255.0redistribute rip subnetsnetwork 192.168.0.0 0.0.0.255 area 0network 172.16.0.0 0.0.0.255 area 1!Related Commands
distance ospf
To define Open Shortest Path First (OSPF) route administrative distances based on route type, use the distance ospf command in router address family topology or router configuration mode. To restore the default value, use the no form of this command.
distance ospf {external dist1 | inter-area dist2 | intra-area dist3}
no distance ospf
Syntax Description
Command Default
dist1: 110
dist2: 110
dist3: 110
Command Modes
Router address family topology configuration (config-router-af-topology)
Router configuration (config-router)Command History
Usage Guidelines
You must specify at least one of the keywords.
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.
Release 12.2(33)SRB
If you plan to configure the Multi-Topology Routing (MTR) feature, you need to enter the distance ospf command in router address family topology configuration mode in order for this OSPF router configuration command to become topology-aware.
Examples
The following example changes the external distance to 200, making the route less reliable:
Router A Configuration
router ospf 1redistribute ospf 2 subnetdistance ospf external 200!router ospf 2redistribute ospf 1 subnetdistance ospf external 200Router B Configuration
router ospf 1 redistribute ospf 2 subnetdistance ospf external 200 ! router ospf 2redistribute ospf 1 subnetdistance ospf external 200Related Commands
domain-id (OSPF)
To change the OSPF domain ID that is used during the redistribution of BGP VPNv4 routes to OSPF, use the domain-id command in router configuration mode. To restore the default value, use the no form of this command.
domain-id {ip-address [secondary] | null | type type-value value hex-value [secondary]}
no domain-id [ip-address [secondary] | null | type type-value value hex-value [secondary]]
Syntax Description
Command Default
The default value for the domain-id command is equal to the OSPF process ID.
Command Modes
Router configuration
Command History
Usage Guidelines
The domain ID is an 8-byte value that identifies the OSPF domain of the prefix. When the OSPF route is redistributed to the BGP VPNv4 route in the MPLS VPN context, the domain ID extended community is attached to the BGP update. The domain ID is used on the egress provider-edge (PE) router, when the BGP VPNv4 route is redistributed to OSPF to decide what type of link-state advertisement (LSA) to generate as a result of the redistribution of the BGP VPNv4 route.
Examples
The following example shows how to change the OSPF domain ID using the domain-id command where the primary domain ID is a valid IP address and the secondary domain ID is a valid hexadecimal value:
Router(config)# router ospf 100 vrf abcdRouter(config-router)# domain-id 10.2.3.4Router(config-router)# domain-id type 0005 value CAFECAFECAFE secondarydomain-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
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
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 grcRouter(config-router)# domain-tag 777The 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 192.168.50.1OSPF Router with ID (192.168.239.66) (Process ID 10)Type-5 AS External Link StatesLS age: 18Options: (No TOS-capability, DC)S Type: AS External LinkLink State ID: 192.168.238.1 (External Network Number)Advertising Router: 192.168.239.66LS Seq Number: 80000002Checksum: 0xDAB0Length: 36Network Mask: /32Metric Type: 2 (Larger than any link state path)TOS: 0Metric: 1Forward Address: 0.0.0.0External Route Tag: 777...OSPF Router with ID (198.168.237.56) (Process ID 1)Related Commands
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 link-state advertisement (LSA) Type 6 Multicast OSPF (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
Usage Guidelines
Cisco routers do not support LSA Type 6 MOSPF packets, 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 109ignore lsa mospfinterface-id snmp-if-index
To configure Open Shortest Path First (OSPF) interfaces with Simple Network Management Protocol (SNMP) MIB-II interface Index (ifIndex) identification numbers, use the interface-id snmp-if-index command in router configuration mode. To revert to the original interface numbering, use the no form of this command.
interface-id snmp-if-index
no interface-id snmp-if-index
Syntax Description
This command has no arguments or keywords.
Command Default
SNMP MIB-II ifIndex numbering for interfaces is disabled.
Command Modes
Router configuration
Command History
Usage Guidelines
The advantage to using SNMP MIB-II ifIndex numbers to identify OSPF interfaces is that the ifIndex number corresponds to the number that a user will see reported by SNMP. Using the SNMP MIB-II ifIndex is also suggested, but not required, by RFC 2328 for OSPFv2 and by RFC 2740 for OSPFv3.
If you want to use the SNMP MIB-II ifIndex numbers, all interfaces that have OSPF enabled must have an SNMP ifIndex number assigned or else OSPF will not be enabled on those interfaces.
Note
Examples
The following example configures the OSPF interfaces to use SNMP MIB-II ifIndex ID numbers. The output from the show snmp mib ifmib ifindex command verifies the configuration.
Router> enableRouter# configure terminalRouter(config)# router ospf 1Router(config-router)# interface-id snmp-if-indexRouter(config-router)# endRouter# show snmp mib ifmib ifindex serial13/0Serial13/0: Ifindex = 53Router# show ip ospf 1 1 data router self-originateOSPF Router with ID (192.168.3.1) (Process ID 1)Router Link States (Area 1)LS age: 66Options: (No TOS-capability, DC)LS Type: Router LinksLink State ID: 192.168.3.1Advertising Router: 192.168.3.1LS Seq Number: 80000003Checksum: 0xE38FLength: 36Number of Links: 1Link connected to: another Router (point-to-point)(Link ID) Neighboring Router ID: 192.168.3.7(Link Data) Router Interface address: 0.0.0.49Number of MTID metrics: 0TOS 0 Metrics: 64Related Commands
show snmp mib ifmib ifindex
Displays SNMP interface index identification numbers (ifIndex values) for all the system interfaces or the specified system interface.
ip ospf area
To enable Open Shortest Path First version 2 (OSPFv2) on an interface, use the ip ospf area command in interface configuration mode. To disable OSPFv2 on the interface, use the no form of this command.
ip ospf process-id area area-id [secondaries none]
no ip ospf process-id area [secondaries none]
Syntax Description
Command Default
If the secondaries none keywords are entered in the no form of this command, the secondary IP addresses will be advertised. If the secondaries none keywords are not present, OSPFv2 will be disabled.
Command Modes
Interface configuration (config-if)
Virtual network interface (config-if-vnet)Command History
Usage Guidelines
OSPF is enabled on an interface when the network address for the interface matches the range of addresses that is specified by the network area command that is entered in router configuration mode. You can enable OSPFv2 explicitly on an interface with the ip ospf area command that is entered in interface configuration mode. This capability simplifies the configuration of unnumbered interfaces with different areas.
The ip ospf area command that is entered in interface configuration mode will supersede the effects of the network area command. Therefore, an interface that is configured with the ip ospf area command in interface configuration mode will not be affected by the network area command.
Note
Examples
The following example enables OSPFv2 on Ethernet interface 0/0/2 and prevents secondary IP addresses from being advertised:
Router(config)# interface Ethernet0/0/2Router(config-if)# ip ospf 10 area 0 secondaries noneRelated Commands
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
Defaults
The area default is no authentication (null authentication).
Command Modes
Interface configuration (config-if)
Virtual network interface (config-if-vnet)Command History
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-digestRelated Commands
ip ospf authentication-key
To assign a password to be used by neighboring routers that are using the Open Shortest Path First (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 (config-if)
Virtual network interface (config-if-vnet)Command History
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
Examples
The following example enables the authentication key with the string yourpass:
ip ospf authentication-key yourpassRelated Commands
area authentication
Enables authentication for an OSPF area.
ip ospf authentication
Specifies authentication type for an interface.
ip ospf bfd
To enable Bidirectional Forwarding Detection (BFD) on a specific interface configured for Open Shortest Path First (OSPF), use the ip ospf bfd command in interface configuration mode. To disable BFD on the OSPF interface, use the disable keyword. To remove the ospf bfd command, use the no form of this command.
ip ospf bfd [disable]
no ip ospf bfd
Syntax Description
Defaults
When the disable keyword is not used, the default behavior is to enable BFD support for OSPF on the interface.
Command Modes
Interface configuration (config-if)
Virtual network interface (config-if-vnet)Command History
Usage Guidelines
Enter the ip ospf bfd command to configure an OSPF interface to use BFD for failure detection. If you have used the bfd-all interfaces command in router configuration mode to globally configure all OSPF interfaces for an OSPF process to use BFD, you can enter the ip ospf bfd command in interface configuration mode with the disable keyword to disable BFD for a specific OSPF interface.
Examples
In the following example, the interface associated with OSPF, Fast Ethernet interface 3/0, is configured for BFD:
Router> enableRouter# configure terminalRouter(config)# interface fastethernet 3/0Router(config-if)# ip ospf bfdRouter(config-if)# endRelated Commands
ip ospf cost
To explicitly specify the cost of sending a packet on an interface, use the ip ospf cost command in interface configuration mode. To reset the path cost to the default value, use the no form of this command.
ip ospf cost interface-cost
no ip ospf cost interface-cost
Syntax Description
interface-cost
Unsigned integer value expressed as the link-state metric. It can be a value in the range from 1 to 65535.
Defaults
No default cost is predefined.
Command Modes
Interface configuration (config-if)
Virtual network interface (config-if-vnet)Command History
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.
•
•
•
•
•
•
•
•
•
•
•
Examples
The following example sets the interface cost value to 65:
ip ospf cost 65ip ospf database-filter all out
To filter outgoing link-state advertisements (LSAs) to an Open Shortest Path First (OSPF) interface, use the ip ospf database-filter all out command in interface configuration mode. To restore the forwarding of LSAs to the interface, use the no form of this command.
ip ospf database-filter all out [disable]
no ip ospf database-filter all out
Syntax Description
disable
(Optional) Disables the filtering of outgoing LSAs to an OSPF interface; all outgoing LSAs are flooded to the interface.
Note
Defaults
This command is disabled by default. All outgoing LSAs are flooded to the interface.
Command Modes
Interface configuration (config-if)
Virtual network interface (config-if-vnet)Command History
Usage Guidelines
This command performs the same function that the neighbor database-filter command performs on a neighbor basis.
If the ip ospf database-filter all out command is enabled for a virtual network and you want to disable it, use the disable keyword in virtual network interface configuration mode.
Examples
The following example prevents flooding of OSPF LSAs to broadcast, nonbroadcast, or point-to-point networks reachable through Ethernet interface 0:
interface ethernet 0ip ospf database-filter all outRelated Commands
ip ospf dead-interval
To set the interval during which at least one hello packet must be received from a neighbor before the router declares that neighbor down, use the ip ospf dead-interval command in interface configuration mode. To restore the default value, use the no form of this command.
ip ospf dead-interval {seconds | minimal hello-multiplier multiplier}
no ip ospf dead-interval
Syntax Description
Defaults
seconds: Four times the interval set by the ip ospf hello-interval command.
Command Modes
Interface configuration (config-if)
Virtual network interface (config-if-vnet)Command History
Usage Guidelines
The dead interval is advertised in OSPF hello packets. This value must be the same for all networking devices on a specific network.
Specifying a smaller dead interval (seconds) will give faster detection of a neighbor being down and improve convergence, but might cause more routing instability.
OSPF Support for Fast Hello Packets
By specifying the minimal and hello-multiplier keywords with a multiplier argument, you are enabling OSPF fast hello packets. The minimal keyword sets the dead interval to 1 second, and the hello-multiplier value sets the number of hello packets sent during that 1 second, thus providing subsecond or "fast" hello packets.
When fast hello packets are configured on the interface, the hello interval advertised in the hello packets that are sent out this interface is set to 0. The hello interval in the hello packets received over this interface is ignored.
The dead interval must be consistent on a segment, whether it is set to 1 second (for fast hello packets) or set to any other value. The hello multiplier need not be the same for the entire segment as long as at least one hello packet is sent within the dead interval.
Use the show ip ospf interface command to verify the dead interval and fast hello interval.
Examples
The following example sets the OSPF dead interval to 20 seconds:
interface ethernet 1ip ospf dead-interval 20The following example configures OSPF fast hello packets; the dead interval is 1 second and there are five hello packets sent every second:
interface ethernet 1ip ospf dead-interval minimal hello-multiplier 5Related Commands
ip ospf hello-interval
Interval between hello packets that the Cisco IOS software sends on the interface.
show ip ospf interface
Displays OSPF-related information.
ip ospf demand-circuit
To configure Open Shortest Path First (OSPF) to treat the interface as an OSPF demand circuit, use the ip ospf demand-circuit command in interface configuration mode or virtual network interface configuration mode. To remove theOSPF demand circuit functionality from the interface, use the no form of this command.
ip ospf demand-circuit [disable] [ignore]
no ip ospf demand-circuit
Syntax Description
Defaults
The circuit is not an OSPF demand circuit.
Command Modes
Interface configuration (config-if)
Virtual network interface (config-if-vnet)Command History
Usage Guidelines
On point-to-point interfaces, only one end of the demand circuit must be configured with the ip ospf demand-circuit command. Periodic hello messages are suppressed and periodic refreshes of link-state advertisements (LSAs) do not flood the demand circuit. This command allows the underlying data link layer to be closed when the topology is stable. In point-to-multipoint topology, only the multipoint end must be configured with this command.
If the ip ospf demand-circuit command is enabled for a virtual network and you want to disable it, use the disable keyword in virtual network interface configuration mode.
Examples
The following example shows how to configure an OSPF demand circuit for an ISDN on-demand circuit:
Router(config)# router ospf 1Router(config-router)# network 10.0.3.0 255.255.255.0 area 0Router(config-router)# exitRouter(config)# interface BRI0Router(config-if)# ip ospf demand-circuitThe following example shows how to prevent OSPF demand circuit operation on a multipoint hub interface:
Router(config)# interface Dialer0Router(config-if)# ip ospf network point-to-multipointRouter(config-if)# ip ospf demand-circuit ignoreRelated Commands
