OSPF protocol configuration command directory

area authenticaion

area default-cost

area range

area stub

area virtual-link

debug ip ospf adj

debug ip ospf events

debug ip ospf flood

debug ip ospf lsa-generation

debug ip ospf packet

debug ip ospf retransmission

debug ip ospf spf

debug ip ospf tree

default-information originate

default-metric

distance ospf

filter

ip ospf cost

ip ospf dead-interval

ip ospf hello-interval

ip ospf message-digest-key

ip ospf network

ip ospf passive

ip ospf password

ip ospf priority

ip ospf retransmit-interval

ip ospf transmit-delay

neighbor

network area

redistribute

router ospf

show ip ospf

show ip ospf border-routers

show ip ospf database

show ip ospf interface

show ip ospf neighbor

show ip ospf virtual-link

summary-address

timers delay

timers hold

 

   This chapter introduces mainly relevant commands of OSPF Which will be Used to configure parameters and monitor the state of OSPF.

area authentication

Use command “area authenticationto authenticate an OSPF area under route configuration mode. Use command “no area area-id authentication to disable the authentication on an area and  no area area-id to delete an area.

area area-id authentication [simple | message-digest]

no area area-id authentication

no area area-id

Parameter:

area-id

Area need to be authenticated

simple

(Alternative 1) Use plaintext method to authenticate.

message-digest

(Alternative 1) Use MD5 method to authenticate.

Default:

It does not have to authenticate when receiving OSPF packet on the interface.

Command mode:

route configuration mode

 

Explanation:

The value of authentication will be written into OSPF packet. Verification types of all routers in the same area should be the same. All OSPF routers in a network should keep same authentication password if they want to communicate with each other.

Example:

The following example show plaintext-authentication on area 0 and 36.0.0.0.

interface ethernet 1/0

ip address 131.119.251.201 255.255.255.0

ip ospf password adcdefgh

!

interface ethernet 1/0

ip address 36.56.0.201 255.255.0.0

ip ospf password ijklmnop

!

router ospf 1

network 36.0.0.0 255.0.0.0 area 36.0.0.0

network 131.119.0.0 255.255.0.0 area 0

area 36.0.0.0 authentication simple

area 0 authentication simple

Relevant command:

ip ospf password

ip ospf message-digest-key

area default-cost

Use “area area-id default-cost cost to designate the cost of default summary routes sent to NSSA or STUB area. If you want to resume the default value of the cost , use command “no area area-id default-cost

area area-id default-cost cost

no area area-id default-cost

no area area-id

Parameter:

area-id

Means ID of stub area

cost

Cost

Default:

Default value is 1.

Command mode:

route configuration mode

Explanation:

This command can only take effect on the area-border routers connected to NSSA or STUB area.

After configuring the command “area stub default-information-originate”, the router will generate LSA (SUM_NET_LSA) containing default router information to relevant stub areas. And the cost configured by this command will be used in this LSA.

Note: If use command “no area area-id” (without any parameter) to delete the area, all subcommand related to the area will be disabled , such as: area authentication, area default-cost, area nssa, area range, area stub, and area virtual-link.

 

Example:

Set default cost of stub network 36.0.0.0 as 20 as the following section:

interface ethernet 1/0

ip address 36.56.0.201 255.255.0.0

!

router ospf 201

network 36.0.0.0 255.0.0.0 area 36.0.0.0

area 36.0.0.0 stub

area 36.0.0.0 default-cost 20

Relevant command:

area nssa
area stub

area range

Summarize routes on area border. Use “no area range to cancel it.

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

no area area-id range address mask
no area area-id

Parameter:

area-id

Referring to the area to process route summary. It could be either a decimal number or an ip address.

address

IP address

mask

IP mask

advertise

To release after being summarized.

not-advertise

Not to release after being summarized.

Default:

It doesn’t work.

Command mode:

route configuration mode

Explanation:

The command area range is only used on Area Border Router.. ABR broadcasts one summarized route to other routers, therefore the route on the border of an area is concentrated and there is only one summarizing route for each address range outside of the area.

This command can be configured on the router with multiple areas. Hence OSPF can summarize several address ranges.

Note: If use command no area area-id (without any parameter) to delete the area, all subcommand related to the area will be disabled , such as: area authentication, area default-cost, area nssa, area range, area stub, and area virtual-link.

Example:

In the following example, area range for sub-network 36.0.0.0 and 192.42.110.0 are configured.

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 36.0.0.0 255.0.0.0 area 36.0.0.0

network 192.42.110.0 255.0.0.0 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

area stub

To configure an area as a stub area. “No area stub command is used to disable the settings.

area area-id stub [no-summary]
no area area-id stub
no area
area-id

Parameter:

area-id

Set the area id of stub area. It can be either a decimal number or an ip address.

no-summary

(Option 1) It is forbidden that ABRrouter sends summarizing link to stub area.

Default:

No stub area is defined.

Command mode:

Route configuration mode

Explanation:

It is necessary to configure “area stub” command on all routers and access severs in the stub area. ABRrouter uses “default-cost option (in command area) to set the cost for the inner router to reach the stub area border.

There are two commands related to stub area : “area xx stub” and “area xx default-cost”. All routers and access severs connected to stub area should be configured with “area stub”.  And sub command “default-cost” is only used on the area border routers connected to stub area. The default-cost option provides the metric for the summary default route generated by the ABR into the stub area.

In order to reduce the number of LSA a little further, no-summary could be used on ABRrouter to prohibit sending summarizing LSA into stub area.

Note: If use command no area area-id (without any parameter) to delete the area, all subcommand related to the area will be disabled , such as: area authentication, area default-cost, area nssa, area range, area stub, and area virtual-link.

Example:

The following example assigns a default cost 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 36.0.0.0 255.255.255.0 area 36.0.0.0

area 36.0.0.0 stub

area 36.0.0.0 default-cost 20

Relevant command:

area authentication
area default-cost

 

area virtual-link

To define an OSPF virtual link, use the area virtual-link router configuration command with the optional parameters. To remove a virtual link, use the no form of this command.

area area-id virtual-link neighbor-ID [dead-interval dead-value][ hello-interval hello-value][ retransmit-interval retrans-value][ transdly dly-value][ password pass-string] [ message-digest-key key-id MD5 md5-string]
no area area-id virtual-link neighbor-ID

Parameters

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.

neighbor-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.

hello-interval seconds

(Optional) Time in seconds between the Hello packets that the router sends on an interface. Unsigned integer value to be advertised in the router's Hello packets. The value must be the same for all routers 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.

transdlyseconds

(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 router'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 attached to a common network.

password

pass-string

(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.

message-digest-key key-id 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 through 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.

 

Default

area-id: No area ID is predefined.
neighbor-id: No router ID is predefined.
hello-interval seconds: 10 seconds
retransmit-interval seconds: 10 seconds
transdly seconds: 1 second
dead-interval seconds: 40 seconds
password key: No key is predefined.
message-digest-key keyid md5 key: No key is predefined.

Command Mode

Ospf Router configuration

Explanation

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.

A router 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.

Examples

The following example establishes a virtual link with default values for all optional parameters:

    router ospf 100
        network 192.168.20.0  255.255.255.0 area 1
        area 1 virtual-link 192.168.20.17

The following example establishes a virtual link with MD5 authentication:

    router ospf 100
        network 192.168.20.0  255.255.255.0 area 1

        area 1 virtual-link 192.168.20.17 mess 100 md5 cx002dxfs
Relevant  Commands

    area authentication
   show ip ospf virtual-link

 

debug ip ospf adj

Monitor the procedure establishing OSPF adjacency:  

debug ip ospf adj

Parameter:

none

Default:

none

Command mode:

supervisor mode

Explanation:

The produce establishing OSPF adjacency could be consulted according to output information of the command.

Example:

Router# debug ip ospf adj

OSPF: Interface 192.168.40.0 on Serial1/0 going down

OSPF NBR: 192.168.40.2 address 192.168.40.2 on Serial1/0 is dead, state DOWN

OSPF NBR: 192.168.40.3 address 192.168.40.3 on Serial1/0 is dead, state DOWN

Line on Interface Serial1/0, changed state to up

Line protocol on Interface Serial1/0 changed state to up

OSPF: Interface 192.168.40.0 on Serial1/0 going Up

OSPF: 2 Way Communication to 192.168.40.2 on Serial1/0, state 2WAY

OSPF: NBR 192.168.40.2 on Serial1/0 Adjacency OK, state NEXSTART.

OSPF: NBR Negotiation Done. We are the SLAVE

OSPF: NBR 192.168.40.2 on Serial1/0 Negotiation Done. We area the SLAVE

OSPF: Exchange Done with 192.168.40.2 on Serial1/0

OSPF: Loading Done with 192.168.40.2 on Serial1/0, database Synchronized (FULL)

OSPF: 2 Way Communication to 192.168.40.3 on Serial1/0, state 2WAY

OSPF: NBR 192.168.40.3 on Serial1/0 Adjacency OK, state NEXSTART.

OSPF: NBR Negotiation Done. We are the SLAVE

OSPF: NBR 192.168.40.3 on Serial1/0 Negotiation Done. We area the SLAVE

OSPF: Bad Sequence with 192.168.40.3 on Serial1/0, state NEXSTART

OSPF: NBR Negotiation Done. We are the SLAVE

OSPF: NBR 192.168.40.3 on Serial1/0 Negotiation Done. We area the SLAVE

OSPF: Exchange Done with 192.168.40.3 on Serial1/0

OSPF: Loading Done with 192.168.40.3 on Serial1/0, database Synchronized (FULL)

……

debug ip ospf events

Monitor events of interface and neighbor:

debug ip ospf events

Parameter:

none

Default:

none

Command mode:

supervisor mode

Explanation:

Events triggered by OSPF interface actions and neighbor operations can be consulted according to  the output information of the command.

Example:

Router# debug ip ospf events

OSPF: Interface Serial1/0 going Up

OSPF: INTF(192.168.40.0) event INTF_UP

OSPF: NBR(192.168.40.2) event HELLO_RX

OSPF: NBR(192.168.40.2) event TWOWAY

OSPF: NBR(192.168.40.2) event ADJ_OK

OSPF: NBR(192.168.40.2) event NEGO_DONE

OSPF: NBR(192.168.40.2) event EXCH_DONE

OSPF: NBR(192.168.40.2) event LOAD_DONE

OSPF: NBR(192.168.40.3) event HELLO_RX

OSPF: NBR(192.168.40.3) event TWOWAY

OSPF: NBR(192.168.40.3) event ADJ_OK

OSPF: NBR(192.168.40.3) event NEGO_DONE

OSPF: NBR(192.168.40.3) event SEQ_MISMATCH

OSPF: NBR(192.168.40.3) event NEGO_DONE

OSPF: NBR(192.168.40.3) event EXCH_DONE

OSPF: NBR(192.168.40.3) event LOAD_DONE

……

debug ip ospf flood

Monitor the flooding process of OSPF link state database:

debug ip ospf flood

Parameter:

none

Default:

none

Command mode:

supervisor mode

Explanation:

The flooding process of OSPF link state database could be viewed according to the command output information.

Example:

Router# debug ip ospf flood

OSPF: recv UPDATE, type 1 LSID 192.168.40.2 ADV_RTR 192.168.40.2 AGE 2 SEQ 0x8000022B

OSPF: Send UPDATE, type 1 LSID 192.168.20.240 ADV_RTR 192.168.20.240 AGE 1 SEQ 0x80000234

OSPF: Send ACK, type 1 LSID 192.168.40.2 ADV_RTR 192.168.40.2 AGE 2 SEQ 0x8000022B

OSPF: recv ACK, type 1 LSID 192.168.20.240 ADV_RTR 192.168.20.240 AGE 1 SEQ 0x80000234

OSPF: recv ACK, type 1 LSID 192.168.20.240 ADV_RTR 192.168.20.240 AGE 18 SEQ 0x80000233

OSPF: Send UPDATE, type 1 LSID 192.168.40.2 ADV_RTR 192.168.40.2 AGE 10 SEQ 0x8000022B

OSPF: recv UPDATE, type 1 LSID 192.168.40.3 ADV_RTR 192.168.40.3 AGE 5 SEQ 0x8000021C

OSPF: Send UPDATE, type 1 LSID 192.168.40.3 ADV_RTR 192.168.40.3 AGE 6 SEQ 0x8000021C

OSPF: Send UPDATE, type 1 LSID 192.168.20.240 ADV_RTR 192.168.20.240 AGE 1 SEQ 0x80000235

OSPF: recv ACK, type 1 LSID 192.168.40.3 ADV_RTR 192.168.40.3 AGE 4 SEQ 0x8000021C

……

debug ip ospf lsa-generation

Supervise the generating process of  LSA of OSPF:

debug ip ospf lsa-generation

Parameter:

none

Default:

none

Command mode:

supervisor mode

Explanation:

The produce of LSA generation can be viewed according to the command output information.

 

Example:

router# debug ip ospf lsa-generation

……

OSPF: Send UPDATE, type 1 LSID 192.168.40.2 ADV_RTR 192.168.40.2 AGE 10 SEQ 0x8000022D

OSPF: recv UPDATE, type 1 LSID 192.168.40.3 ADV_RTR 192.168.40.3 AGE 5 SEQ 0x8000021E

OSPF: Send UPDATE, type 1 LSID 192.168.40.3 ADV_RTR 192.168.40.3 AGE 6 SEQ 0x8000021E

OSPF: Send UPDATE, type 1 LSID 192.168.20.240 ADV_RTR 192.168.20.240 AGE 1 SEQ 0x80000239

OSPF: recv ACK, type 1 LSID 192.168.40.3 ADV_RTR 192.168.40.3 AGE 4 SEQ 0x8000021E

OSPF: Send ACK, type 1 LSID 192.168.40.3 ADV_RTR 192.168.40.3 AGE 5 SEQ 0x8000021E

OSPF: recv UPDATE, type 1 LSID 192.168.40.2 ADV_RTR 192.168.40.2 AGE 1 SEQ 0x8000022E

OSPF: Send UPDATE, type 1 LSID 192.168.40.2 ADV_RTR 192.168.40.2 AGE 2 SEQ 0x8000022E

OSPF: recv ACK, type 1 LSID 192.168.20.240 ADV_RTR 192.168.20.240 AGE 1 SEQ 0x80000239

OSPF: recv ACK, type 1 LSID 192.168.40.3 ADV_RTR 192.168.40.3 AGE 6 SEQ 0x8000021E

OSPF: recv ACK, type 1 LSID 192.168.20.240 ADV_RTR 192.168.20.240 AGE 1 SEQ 0x80000239

……

debug ip ospf packet

Supervise the packet of ospf:

debug ip ospf packet

Parameter:

none

Default:

none

Command mode:

supervisor mode

Explanation:

Senging/Receiving all kind of OSPF packet can be viewed according to the command output information.

Example:

router# debug ip ospf packet

OSPF: Recv HELLO packet from 192.168.40.3 (addr: 192.168.40.3) area 0 from Serial1/0

OSPF: End of hello processing

OSPF: Send HELLO to 224.0.0.5 on Loopback0

     HelloInt 10 Dead 40 Opt 0x2 Pri 1 len 44

OSPF: Send HELLO to 224.0.0.5 on Loopback0

     HelloInt 10 Dead 40 Opt 0x2 Pri 1 len 44

OSPF: Send HELLO to 224.0.0.5 on Loopback0

     HelloInt 10 Dead 40 Opt 0x2 Pri 1 len 44

OSPF: Recv HELLO packet from 192.168.40.2 (addr: 192.168.40.2) area 0 from Serial1/0

OSPF: End of hello processing

OSPF: Send HELLO to 224.0.0.5 on Serial1/0

     HelloInt 30 Dead 120 Opt 0x2 Pri 1 len 52

OSPF: Recv HELLO packet from 192.168.40.3 (addr: 192.168.40.3) area 0 from Serial1/0

OSPF: End of hello processing

OSPF: Send HELLO to 224.0.0.5 on Loopback0

     HelloInt 10 Dead 40 Opt 0x2 Pri 1 len 44

……

debug ip ospf retransmission

Supervise the packet- retransmission process of ospf:

debug ip ospf retransmission

Parameter:

none

Default:

none

Command mode:

supervisor mode

Explanation:

Retransmiting OSPF packets can be viewed according to command output information.

Example:

router# debug ip ospf retransmission

OSPF: retransmit UPDATE to 192.168.40.3 (RID 192.168.40.3), state FULL

……

debug ip ospf spf

Supervise the SPF calculation of OSPF:

debug ip ospf spf

debug ip ospf spf intra

debug ip ospf spf inter

debug ip ospf spf external

Parameter:

none

Default:

none

Command mode:

supervisor mode

Explanation:

The SPF calculation process can be viewed according to command output information.

Example:

router# debug ip ospf spf

OSPF: run ospf_spf_run

OSPF: start doing SPF for AREA 0.0.0.0

OSPF: RTAB_REV(ospf) 1390.

OSPF : Initializing to do SPF

OSPF: addroute LSID 192.168.20.240

OSPF: ospf_nh_find: 192.168.40.2

……

OSPF: addroute LSID 192.168.40.3

OSPF: build a OSPF_ROUTE, dest: 192.168.40.3

OSPF: addroute LSID 192.168.40.2

……

OSPF: SPF Area A running Network Summary

OSPF: Processing LS_SUM_NET 192.168.40.24, mask 255.255.255.248, adv 192.168.40.3, age 599

OSPF: addroute LSID 192.168.40.24

OSPF: ospf_build_route RT 192.168.40.24

OSPF: build route 192.168.40.24(255.255.255.248).

……

OSPF: Processing LS_SUM_NET 1.1.1.1, mask 255.255.255.255, adv 192.168.20.240, age 228

OSPF: addroute LSID 192.168.20.236

OSPF: build a OSPF_ROUTE, dest: 192.168.20.236

OSPF: start Building AS External Routes

OSPF: processing LS_ASE 192.168.42.0, mask 255.255.255.248, adv 192.168.20.236, age 258

OSPF: addroute LSID 192.168.42.0

OSPF: ospf_build_route RT 192.168.42.0

OSPF: build route 192.168.42.0(255.255.255.248).

OSPF: processing LS_ASE 192.168.43.0, mask 255.255.255.0, adv 192.168.20.236, age 258

OSPF: addroute LSID 192.168.43.0

OSPF: ospf_build_route RT 192.168.43.0

OSPF: build route 192.168.43.0(255.255.255.0).

OSPF: processing LS_ASE 192.168.44.0, mask 255.255.255.0, adv 192.168.20.236, age 258

OSPF: addroute LSID 192.168.44.0

OSPF: ospf_build_route RT 192.168.44.0

OSPF: build route 192.168.44.0(255.255.255.0).

……

OSPF: end doing SPF for AREA 0.0.0.0

Display field decryption

Field

Description

LSA(192.168.20.236, LS_SUM_ASB)

ID and type of LSA

debug ip ospf tree

Supervise the establishment of SPF tree of OSPF:

debug ip ospf tree

Parameter:

none

Default:

none

Command mode:

supervisor mode

Explanation:

The establishment of SPF tree of OSPF can be viewed according to command output information.

Example:

router# debug ip ospf tree

B3710_221#

OSPF: add LSA(192.168.40.0, LS_STUB) 1600 under LSA(192.168.20.240, LS_RTR)

OSPF: add LSA(192.168.40.2, LS_RTR) 1600 under LSA(192.168.20.240, LS_RTR)

OSPF: add LSA(192.168.40.3, LS_RTR) 1600 under LSA(192.168.20.240, LS_RTR)

OSPF: add LSA(192.168.40.1, LS_STUB) 0 under LSA(192.168.20.240, LS_RTR)

OSPF: add LSA(192.168.40.3, LS_STUB) 1600 under LSA(192.168.40.3, LS_RTR)

OSPF: add LSA(192.169.1.5, LS_RTR) 3200 under LSA(192.168.40.2, LS_RTR)

OSPF: add LSA(192.168.40.18, LS_STUB) 1600 under LSA(192.168.40.2, LS_RTR)

OSPF: add LSA(192.168.40.2, LS_STUB) 1600 under LSA(192.168.40.2, LS_RTR)

OSPF: add LSA(192.168.40.17, LS_STUB) 3200 under LSA(192.169.1.5, LS_RTR)

OSPF: add LSA(192.168.40.24, LS_SUM_NET) 1601 under LSA(192.168.40.3, LS_RTR)

OSPF: add LSA(192.168.40.32, LS_SUM_NET) 3200 under LSA(192.168.40.2, LS_RTR)

OSPF: add LSA(192.168.40.40, LS_SUM_NET) 14577 under LSA(192.169.1.5, LS_RTR)

OSPF: add LSA(192.168.20.236, LS_SUM_ASB) 3200 under LSA(192.168.40.2, LS_RTR)

show field description

Field

Description

LSA(192.168.20.236, LS_SUM_ASB)

ID and type of LSA

add

sub-LSA

under

parent LSA

 

default-information originate (OSPF)

Generate a default route into OSPF routing domain

default-information originate [always] [route-map map-name]
no default-information originate [always] [route-map map-name]

Parameter:

originate

Use this command, if there has been a default route and it is expected to be transmitted to other routers. This parameter will cause the system to transmit an external route into OSPF routing domain.

Always

(Option) Whether the system has a default route or not, the system will broadcast the default route.

route-map map-name

(Option) If route-map is met, a default route will be generated.

Default:

default route is not generated

Command mode:

route configuration state

Explanation:

Use either command “redistribute or command “default-information to distribute a route to OSPF routing domain. The router will become ASBR. But ASBR doesn’t generate a default route into OSPF routing domain in default case, unless “always” option has been set, otherwise a default route should be configured.

When this command is used, the default network should be contained in the routing table and must satify condition of the option route-map. If you dont want the dependency on the default network in routing table, use command default-information originate always route-map.

Example:

The following example shows the default route distributed into OSPF routing domain:

router ospf 109

redistribute rip

default-information originate

Relevant command:

Redistribute

default-metric

Set the default metric value for the route introduced . Use no default-metric to reset the default value.

default-metric value

no default-metric

Parameter:

The route Metric to be set is value with a range from 1 to 4294967295.

Default:

The default route Metric is 10.

Command mode:

route configuration state

Explanation:

The command default-metric is used to set the default Metric that is used to introduce the route of other routing protocol into ospf routing domain. When using the command redistribute to introduce the route of other routing protocol, the default Metric designated by default-metric is used if no specific route value is designated.

Example:

Set the default metric value to 3 to distribute routes of other routing protocol.

router_config_ospf_100#default-metric 3

Relevant command:

redistribute

distance ospf

Define the administrative administrative distance according to the type. Use “no distance ospf” to disable the settings.

distance ospf {[intra-area dist1] [inter-area dist2] [external dist3]}
no distance ospf [intra-area] [inter-area] [external]

Parameter:

intra-area dist1

(Option) Set the distance for all routes of an area. The default value is 110.

inter-area dist2

(Option)Set the distance for all routes from an area to another area. The default value is 110.

external dist3

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

Default:

intra-area: 110
inter-area: 110
external: 150

Command mode:

route configuration state

Explanation:

Should have at least one parameter.

This command has the same function as “distance. However command “distance ospf can configure the distance of the whole route group not only the route passing through a certain access list.

Example:

The following example set external distance as 200.

Router A

router ospf 1

redistribute ospf 2

distance ospf external 200

!

router ospf 2

redistribute ospf 1

distance ospf external 200

Router B

router ospf 1

redistribute ospf 2

distance ospf external 200

!

router ospf 2

redistribute ospf 1

distance ospf external 200

Relevant command:

distance

filter

Use route configuration state command “filter” to set route filtering list. Use command “no filter” to reset the default settings.                 

filter {interface-type interface-number | *} {in } {access-list access-list-name | gateway access-list-name | prefix-list prefix-list-name}

filter {interface-type interface-number | *} {in } {access-list access-list-name | gateway access-list-name | prefix-list prefix-list-name}

Parameter:

interface-type

Interface type

interface-number

interface number

*

All interfaces

access-list-name

Name of the access list

access-list-name

name of the access list

prefix-list-name

Name of the prefix list

Default:

none

Command mode:

route configuration state

Explanation:

none

Example:

filter * in access-list mylist 

 

ip ospf cost

Designate the cost needed for the interface to run OSPFprotocol. Command no ip ospf cost is used to reset the default value.

ip ospf cost cost

no ip ospf cost

Parameter:

cost is the value to be spent for OSPFprotocol, ranging from 1to 65535 (whole number).

Default:

The default value of the cost is calculated according to the rate of the interface.

 

Command mode:

interface configuration state

Example:

Set the value of the cost to 2 on the interface serial 0 for OSPF.

ip ospf cost 2

Designate the cost needed for interface to run OSPFprotocol. Command no ip ospf cost is used to reset the default value.

ip ospf dead-interval

Designate the time length to recognize the death of neighboring routers. Command “no ip ospf dead-interval” is used to reset default value.

 

ip ospf dead-interval seconds

no ip ospf dead-interval

Parameter:

Seconds is the time value of the death of neighboring routers, which is calculated in seconds. The legal range is 1 ~ 65535

Default:

The default time length of the death of neighboring routers on the interface is 40 seconds.

Command mode:

interface configuration state

Explanation:

Value of dead-interval will be written into Hello packet and will be sent together with hello packet. It should be ensured that the dead-interval is in accordance with the dead-interval set in the hello packet by other adjacent neighbors on the interface and is 4 times the value of Hello-interval.

Example:

Configure dead-interval of neighboring routers on interface Serial0 as 60 seconds.

router_config_S1/0#ip ospf dead-interval 60

Relevant command:

ip ospf hello-interval

ip ospf hello-interval

Designate the interval to send Hello packet on the interface. Command no ip ospf hello-interval reset the default value.

ip ospf hello-interval seconds

no ip ospf hello-interval

Parameter:

“Seconds” is the interval to send HELLO packet and is calculated in seconds. The range is from 1 to 255.

Default:

The default interval to send HELLO packet on the interface is 10 seconds.

Command mode:

interface configuration mode

Explanation:

The value of the hello-interval will be written into the HELLO packet and will be sent together with the HELLO packet. The smaller the value of hello-interval is, the more quickly the topology of the network will be found and the more the router cost will cost. It should be ensured that the value of hello-interval is in accordance with the hello-interval set by other adjacent neighbors on the interface.

Example:

Configure the interval to send HELLO packet on interface Serial1/0 as 20 seconds.

router_config_S1/0#ip ospf hello-interval 20

Relevant command:

ip ospf dead-interval

ip ospf message-digest-key

Set that ospf applies MD5 authentication. Use “no ip ospf message-digest-key to disable the setting.。

ip ospf message-digest-key keyid md5 key
no ip ospf message-digest-key keyid

Parameter:

keyid

Authenticate ID(1 255).

key

16-digit letter and number  string

Default:

OSPF MD5 authentication is not used.

Command mode:

interface configuration mode

Explanation:

Usually each interface uses a key value to generate authentication information or validate the package received. Both adjacent routers should have the same key.

The process to change the key is as follows.

If the current configuration is as the following:

interface ethernet 1

ip ospf message-digest-key 100 md5 OLD

Change it into the following configuration:

interface ethernet 1

ip ospf message-digest-key 101 md5 NEW

The system assumes its neighboring router has no new key either. It will send the same package in many copies. Each copy applies different key value. This example router will send each package in 2 copies with one copys key=100 and the other one key=101.

This allows the neighboring routers to continue to communicate when the manager is revising a key value. The process stops as soon as it is found that all adjacencies apply a new key value. When the system receives packages with a new key value sent by neighboring router, it will recognize that neighboring router has a new key.

After all neighbors have applied a new key, the old key will be deleted. In this example, it should be configured as the following:

interface ethernet 1/0

no ip ospf message-digest-key 100

Thus the Ethernet interface 1/0 can only apply key=101 to make the authentication.

Suggest that each interface had better not to have several keys. Former key value should be deleted after new key value is added to prevent that local system uses former key to communicate with unfriendly system knowing the former system. Deleting the former key value will also reduce the communication burden.

Example:

The following example sets a new key=19. The password is 8ry4222:

interface ethernet 1

ip ospf message-digest-key 10 md5 xvv560qle

ip ospf message-digest-key 19 md5 8ry4222

Relevant command:

area authentication

ip ospf network

Set network type of the interface. command “no ip ospf network” is used to disable the setting.

ip ospf network { broadcast | nonbroadcast | point_to_multipoint | point-to-point}

no ip ospf network { broadcast | nonbroadcast | point_to_multipoint | point-to-point}

Parameter:

broadcast

Set the network type of interface as broadcast type.

nonbroadcast

Set the network type of interface as non-broadcast NBMA type.

point-to-point

Set the network type of interface as the point-to-point type.

point-to-multipoint

Set the network type of interface as point-to-multipoint type.

Command mode:

interface configuration mode

Explanation:

On the broadcast network without multi-address access ability, the interface should be configured as NBMA type. If it cannot be ensured that any two routers on a NBMA network are accessible to each other, the network should be set as point-to-multipoint type.

Example:

Configure the interface Serial1/0 as non-broadcast NBMA type.

router_config_S1/0#ip ospf network nonbroadcast

 

ip ospf passive

Use command “ip ospf passive” to disable sending HELLO packet on the interface. Use “no ip ospf passive” to enable sending HELLO packet.

ip ospf passive
no ip ospf passive

Parameter:

none

Default:

Send HELLO massage on interface.

Command mode:

interface configuration mode

Explanation:

If you disable sending HELLO massage on a certain interface, a specific sub network will continue to announce to other interfaces and route update from other router to this interface will continue to be accepted and processed. This is usually used on STUB network. There usually aren’t any other OSPFrouter on such a network.

Example:

The following example sends HELLO packet for network 131.108.0.0 to all interfaces (excluding Ethernet interface 1/0):

interface ethernet 1/0

ip address 172.16.0.1 255.255.0.0

ip ospf passive

router ospf 110

network 172.16.0.0 255.255.0.0 area 1

 

ip ospf password

Configure password for plain-text authentication on the interface . Use “no ip ospf password to disable the setting.

ip ospf password password
no ip ospf password

Parameter:

password

Any sequential 8-digit character string.

Default:

No Password

Command mode:

interface configuration mode

Explanation:

The password generated from this command inserts route information package directly. You can configure one password for each netework on each interface. All neighbors on the interface should have the same password to exchange route information.

Note: This command will validate only after the command “area authentication configured.

Example:

ip ospf password yourpass

Relevant command:

area authentication

ip ospf priority

Configure the priority for electing DR router on the interface. Use no ip ospf priority to reset the default value.

ip ospf priority priority

no ip ospf priority

Parameter:

priority refers to the priority with rightful range from 0 to 255.

Default:

The default priority of the interface for electing DR router is 1.

Command mode:

interface configuration mode

Explanation:

When both routers connected to the same section of a network want to become DR, choose the one with a higher priority. If they share the same priority, choose the one with the bigger router ID number. A router with priority 0 will not be elected as “DR” or “BDR”. The priority will validate only when it is configured on non-point-to-point network.

Example:

Set the priority of interface Serial1/0 for electing DR as 8.

router_config_S1/0#ip ospf priority 8

Relevant command:

neighbor

ip ospf retransmit-interval

Designate the retransmission interval for transmitting link state packet to the adjacent neighbor on the interface. Command “no ip ospf retransmit reset the default value.

ip ospf retransmit seconds

no ip ospf retransmit

Parameter:

seconds” is the retransmit interval for transmitting link state broadcast between interface and neighboring router and is calculated in seconds. Its range is from 1 to 65535.

Default:

The default retransmission interval for transmitting link state broadcast between interface and neighboring router is 5 seconds.

Command mode:

interface configuration mode

Explanation:

When a router send link state broadcast to its neighboring router, it will keep the link state packet until receiving confirmation from its neighbor. If confirmation is not received within the interval “seconds, it should be retransmitted. Value of “seconds” should be longer than the round-trip time between the routers.

Example:

Configurate the retransmit interval for transmitting link state broadcast between interface Serial1/0 and neighboring router as 8 seconds.

router_config_S1/0#ip ospf retransmit 8

ip ospf transmit-delay

Configure the time delay value for transmitting link state broadcast on the interface. Use “no ip ospf transit-delay” to reset the default value.

ip ospf transit-delay time

no ip ospf transit-delay

Parameter:

Configurate the retransmit interval for transmitting link state broadcast between interface Serial1/0 and neighboring router as 8 seconds.

Default:

The default time delay value for transmitting link state broadcast on the interface is 1 second.

Command mode:

interface configuration mode

Example:

Configure the time delay value for transmitting link state broadcast on interface Serial1/0 as 3 seconds.

router_config_S1/0#ip ospf transit-delay 3

 

neighbor

Configure the OSPFrouter in adjacency with non-broadcast network. Use “no neighbor” to delete it.

neighbor ip-address [priority number] [poll-interval seconds] [cost number]
no neighbor
ip-address [priority number] [poll-interval seconds] [cost number]

 

Parameter:

ip-address

IP address of neighboring router.

priority number

 (Option 1) 8-digit priority. Default value is 0. This option cannot be used for point-multipoint interface.

poll-interval seconds

 (Option 1) Referring to poll interval. Suggest that it should be longer than hello interval for RFC 1247. This option cannot be used for point-multipoint interface.

cost number

 (Option 1) Designate cost (1-65535) for neighboring router. If the cost is not designated, use the cost designated by “ip  ip  ospf co”. This option is the only one that works for a point-multipoint network. It is not fitted for NBMA network.

Default:

none

Command mode:

router configuration mode

Explanation:

For X25 and frame relay network, you can set OSPF to work with broadcast type. Referring to the following for the details:

Command  X25 map and frame-relay map

For each non-broadcast neighbor, the configuration should be configured within the router. The neighbor address should be the main address of the interface.

If the neighboring router is in a non-active state, it is still necessary to send hello packages to it. These hello packages will be sent at poll interval.

When turning on the router, a hello package is only sent to the router with a non-zero priority. This router can be changed into DR and BDR routers. When DR and BDR routers are selected, DR and BDR routers will send hello package all neighbor to form adjacencies

Example:

The following example designate router 131.108.3.4 address as non-broadcast network with priority 1 and poll interval 180 seconds.

router ospf

neighbor 131.108.3.4 priority 1 poll-interval 180

The following example refers to the configuration of point-to-multipoint non-broadcast network.

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 10.0.1.0 255.255.255.0 area 0

neighbor 10.0.1.3 cost 5

neighbor 10.0.1.4 cost 10

neighbor 10.0.1.5 cost 15

Relevant command:

ip ospf priority

network area

Start OSPF on the interface if it is covered by the network, and specify the area ID. Command “no network” is used to disable network.

network network mask area area_id [ advertise | not-advertise ]

[ no ] network network mask area area_id [ advertise | not-advertise ]

Parameter:

“Network” and “mask” are network IP address and mask with dotted decimal notation.

area_id is the area number.

Default:

The default of the system doesn’t configure the network range.

Command mode:

route configuration mode

Explanation:

Once a network range is added in the area, all internal routes of IP addresses reaching the network range within the area will not be broadcast to other areas individually. Only abstract information of routes within the whole network range. Introducing network range and restriction to the network range will reduce the communication between routes of different areas.

Example:

Define network range 10.0.0.0 255.0.0.0 and add it into area 2.

router_config_ospf_10#network 10.0.0.0 255.0.0.0 area 2

redistribute

Use route configuration state command “redistribute” to set ospf to redistribute route of other routing protocol. Use command “no redistribute” to reset default setting.

redistribute protocol [as-number]  [route-map map-tag]
no redistribute protocol [as-number]
  [route-map map-tag]
 

Parameter:

Protocol

The source protocol to be distributed can only be one of the following: beigrp, bgp, connect, ospf, rip and static . 

as_number

 (Optional) Autonomous system number. There is no such a parameter for connect, rip and static.

map-tag

 (Optional) Name of route-map

Default:

dont redistribute

 

Command mode:

route configuration mode

Explanation:

none

Example:

Redistribute ospf 0 (redistribute ospf routes in process 0)

 

router ospf

Enable OSPF routing protocol on the router. Use “No router ospf” to prohibit routers from using ospf.

router ospf process-id
no router ospf process-id

Parameter:

process-id

The parameter used to mark OSPF router process internally. It is a non-negative integer allocated locally. It uniquely refers to a route processing process.

Default:

No ospf route processing is defined.

Command mode:

global configuration mode

Explanation:

There can be several ospf route-processing processes in a router.

Example:

An ospf route process with ID 109 is configured as the following.

router ospf 109

Relevant command:

network area

show ip ospf

Show main information of OSPF.

show ip ospf [process-id]

Parameter:

process-id alternative)process number

Default:

none。

Command mode:

supervisor mode

Explanation:

The command output information can be used to help users to diagnose OSPF failure. With process-id, only global configuration information of corresponding OSPF process will be shown.

Example:

    Show all configuration information of OSPF process:

router#show ip ospf

OSPF process: 1, Router ID is 192.168.99.81

Distance: intra-area 110 inter-area 130 external 150

Source Distance Access-list

240.240.1.1/24 1 what

SPF schedule delay 5 secs, Hold time between two SPFs 10 secs

Number of areas is 3

AREA: 1

Number of interface in this area is 1(UP: 1)

Area authentication type: None

AREA: 36.0.0.1

This is a stub area.

Number of interface in this area is 0(UP: 0)

Area authentication type: None

AREA: 192.168.20.0

Number of interface in this area is 0(UP: 0)

Area authentication type: None

Net Range list:

10.0.0.0/255.0.0.0 Not-Advertise

140.140.0.0/255.255.0.0 Advertise

filter list on receiving UPDATE is Gateway: weewe

filter list on sending UPDATE is Prefix: trtwd

Summary-address list:

150.150.0.0/16 advertise

router#

Show field description.

Area

Description

OSPF process: 1

ID of OSPF process

Router ID is 192.168.99.81

ID of router

Distance: intra-area 110 inter-area 130 external 150

Default administrative distance adopted when the routing is generated by current router

Source Distance Access-list

Administrative distance based on access list configured

SPF schedule delay 5 secs, Hold time between two SPFs 10 secs

Two 0SPF related TIMER values

Number of areas is 3

The number of area configured currently and parameter configured in each area

filter list on receiving

Filter configured for imported route

filter list on sending

Filter configured for exported route

Summary-address list

route summarizing configured

 

show ip ospf border-routers

Show data item of ABR and ASBR in router.

show ip ospf border-routers

Parameter:

none

Default:

none

Command mode:

supervisor mode

Example:

router#

router#sh ip os bor

OSPF process: 1

Codes: i - Intra-area route, I - Inter-area route

Destination Adv-Rtr Cost Type Area

i 192.168.20.77 192.168.20.77 11 ABR 0

router#

Show field description

Field

Description

Destination

ID of target router

Adv-Rtr

Next hop to reach target router

Cost

Cost of using this route.

Type

Type of target router. It can be ABR, ASBR or both of them.

Area

Area ID from which the router is learned.

show ip ospf database

show OSPF link state database information

show ip ospf database

Parameter:

none

Default:

none

Command mode:

supervisor mode

Explanation:

OSPF link state database information can be viewed according to this command. It will help the users to diagnose the failure.

Example:

router#

router#show ip ospf database

OSPF process: 1

(Router ID 192.168.99.81)

AREA: 0

Router Link States

Link ID ADV Router Age Seq # Checksum Link count

192.168.20.77 192.168.20.77 77 0x8000008a 0x90ed 1

192.168.99.81 192.168.99.81 66 0x80000003 0xd978 1

Net Link States

Link ID ADV Router Age Seq # Checksum

192.168.20.77 192.168.20.77 80 0x80000001 0x9625

Summary Net Link States

Link ID ADV Router Age Seq # Checksum

192.168.99.0 192.168.99.81 87 0x80000003 0xd78c

AREA: 1

Router Link States

Link ID ADV Router Age Seq # Checksum Link count

192.168.99.81 192.168.99.81 70 0x80000002 0x0817 1

Summary Net Link States

Link ID ADV Router Age Seq # Checksum

192.168.20.0 192.168.99.81 66 0x80000006 0xd1c1

Show field description

Field

Description

AREA: 1

the area where it is in

Router Link States/Net Link States/Summary Net Link States

LSA type

Link ID

LSA ID.

ADV Router

Advertising router

Age

LSA age

Seq #

Sequence number

Checksum

checksum value

show ip ospf interface

Show OSPF interface information.

show ip ospf interface

Parameter:

none

Default:

none

Command mode:

supervisor mode

Explanation:

View configuration and running state of OSPF on the interface.

Example:

router#sh ip os int

Ethernet 1/0 is up, line protocol is up

Internet Address: 192.168.20.81/24, Nettype: BROADCAST

OSPF process is 1, AREA 0, Router ID 202.96.135.201

Cost 10, Transmit Delay is 1 sec, Priority 1

Hello interval 10, Dead timer 40, Retransmit 5

OSPF INTF State is DrOther

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

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)

router#

show field description

Field

Description

Internet Address:

IP address of the interface

Nettype

OSPF interface network type

OSPF process is

The process number of the OSPF

AREA

the area where it is

Router ID

router ID of the process where it is

Cost

interface cost

Transmit Delay is

transmit delay

Priority

priority of the router interface

Hello interval

hello interval

Dead timer

dead time

Retransmit

retransmit interval

OSPF INTF State is

OSPF interface state

Designated Router id

Router ID of DR and IP address of the interface on DR

Backup Designated router id

Router ID of BDR and IP address of the interface on BDR

Neighbor Count is

number of neighboring routers

Adjacent neighbor count is

number of the neighbors that have established adjacency

Adjacent with neighbor

list of the neighbors that have established adjacency

show ip ospf neighbor

Show OSPF adjacency point information

show ip ospf neighbor

Parameter:

none

Default:

none。

Command mode:

supervisor mode

Explanation:

The information of OSPF neighbors can be viewed according to command output. It will help the user to make sure if OSPF neighbor configuration is right and diagnose OSPF failure.

Example:

router#show ip ospf neighbor

OSPF process: 1

AREA 1

Neighbor Pri State DeadTime Address Interface

21.0.0.32 1 FULL /DR 31 192.168.99.32 Ethernet1/0

AREA 36.0.0.1

Neighbor Pri State DeadTime Address Interface

199.199.199.137 1 EXSTART/DR 31 202.19.19.137 Ethernet2/1

AREA 192.168.20.0

Neighbor Pri State DeadTime Address Interface

140.140.0.46 1 FULL /DR 108 140.140.0.46 Serial 1/0

133.133.2.11 1 FULL /DR 110 133.133.2.11 Serial1/0

192.31.48.200 1 FULL / DROTHER 31 192.31.48.200 Ethernet1/0

show field description

Field

description

OSPF process

number of the process of OSPF where it is

AREA

the area where it is

Neighbor

ID of the neighbor

Pri

priority of the neighbor

State

the state of the connection with the neighbor

DeadTime

time of invalidation of the neighbor

Address

IP address of the neighbor

Interface

interface used by router to reach the neighbor

 

show ip ospf virtual-link

To display parameters about and the current state of OSPF virtual links, use the show ip ospf virtual-link command.

show ip ospf virtual-link

Parameters

This command has no arguments or keywords.

Command Mode

supervisor mode

Explanation

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

Example

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

RouterA#show ip ospf vir

Virtual Link Neighbor ID 200.200.200.200 (UP)

  TransArea: 1, Cost is 1600

  Hello interval is 10, Dead timer is 40  Retransmit is 5

  INTF Adjacency state is IPOINT_TO_POINT

 

Show field Description

 

Field

Description

Virtual Link Neighbor ID 200.200.200.200 (UP)

Specifies the OSPF neighbor, and if the link to that neighbor is Up or Down.

TransArea: 1

The transit area through which the virtual link is formed.

Cost is 1600

The cost of reaching the OSPF neighbor through the virtual link.

Hello interval is 10

The hello interval on this virtual-link.

Dead timer is 40

The dead interval on this virtual-link.

Retransmit is 5

The retransmit interval on this virtual link.

INTF Adjacency state is IPOINT_TO_POINT

The state of this virtual link interface.

summary-address

Use route configuration state command “summary-address” to establish route summary address for OSPF. Use route configuration state command “no summary-address” to delete route summary address.

summary-address address mask [not-advertise]
no summary-address address mask

Parameter:

address

Network for summary.

Mask

Sub network Mask of summarizing route.

not-advertise

 (Optional) It is used to restrain the generation of LSA from matched routes.

Default:

none

Command mode:

route configuration mode

Explanation:

There can be groups of addresses to be summarized. The route learned from other routing protocol can also be summarized. After being summarized, all networks covered by it will not be transmitted to other route area. The cost for the summary route is the smallest one among routes summarized. This command can reduce the route number in the routing table.

Using this command for OSPF will cause the OSPF autonomous system border routerASBRto inform an exterior route into OSPF domain for these routes distributed from exterior networks covered by the network configured. This command can only summarize routes entering into OSPF by redistributing from other routing protocol.  area range can be used to summarize routes in OSPF domain.

Example:

In the following example, summarized address 10.1.0.0 represents 10.1.1.0, 10.1.2.0, 10.1.3.0,etc. only address 10.1.0.0 is broadcasted.

summary-address 10.1.0.0 255.255.0.0

Relevant command:

area range
ip ospf password
ip ospf message-digest-key

timers delay

Use route configuration state command “timer delay” to designate the time we could delay for SPF calculation after receiving a topology change. Use command “no timers delay” to reset the default settings.

timers delay spf-delay
no timers delay

Parameter:

spf-delay

Time delay in seconds between the topology changing and SPF starting calculation. The range is from 0 to 65535. Default value is 5 seconds. If it is 0 second, it means no time delay. Recalculate at once if there is any change.

Default:

spf-delay: 5 seconds

Command mode:

route configuration mode

Explanation:

The less the setting time is, the more quickly it reflects the change of the network topology. But it will take more time of the processor.。

Example:

timers spf 10

timers hold

Use route configuration command timers hold to set interval between two sequential calculations for OSPF. Use command no timers spf to reset the default setting.

timers hold spf-holdtime
no timers hold

Parameter:

spf-holdtime

The smallest value between the two sequential calculations. The range is from 0 to 65535. The default is 10 secnds. If it is 0, it means that there is no interval between the two calculations.

Default:

spf-holdtime: 10  seconds

 

Command mode:

route configuration mode

Explanation:

The less the setting time is, the more quickly to reflect the change of the network topology. But it will take more time of the processor.

Example:

timers spf 20