Configuring Additional Parameters

The commands presented in this section include both OSPF-specific commands and routing protocol-independent commands that are not limited to OSPF. You can use these commands to perform the following tasks listed in Table 8-3:

Table 8-3 Additional configuration tasks

Filter and apply policy to routes.	Set the maximum paths.
Set a baseline for statistics.	Enable automatic cost calculation.
Set the redistribution routes.	Enable logs for OSPF neighbor changes.
Set the distance for OSPF routes.	Set SPF hold time.
Administratively disable OSPF.	Set a default metric.

    access-list
    route-map

• Use the access-list command to create a standard or extended access list.
• Use the route-map command to create a route map.
• For detailed information on configuring access lists and route maps, see Chapter 1, Configuring Routing Policy.
• Example

1    Configure three static routes:

host1(config)#ip route 20.20.20.0 255.255.255.0 192.168.1.0

host1(config)#ip route 20.20.21.0 255.255.255.0 192.168.1.0

host1(config)#ip route 20.21.0.0 255.255.255.0 192.168.1.0

2    Configure an access list with filters on routes 20.20.20.0/24 and 20.20.21.0/24:

host1(config)#access-list boston permit 20.20.0.0 
0.0.255.255

3    Configure a route map which matches the previous access list and applies a metric type 1 (OSPF):

host1(config)#route-map boston 

host1(config-route-map)#match ip address boston

host1(config-route-map)#set metric-type type-1

4    Configure redistribution of the static routes into OSPF with route map boston:

host1(config)#router ospf 2 

host1(config-router)#redistribute static route-map boston

5    Use the show ip ospf database command to verify the effect of the redistribution (the two static routes matching the route map are redistributed as external type 1):

host1#show ip ospf database

    OSPF Database

      Router Link States (Area 0.0.0.0)

Link ID         ADV Router      Age         Seq#        Checksum

192.168.1.250   192.168.1.250   3           0x80000006  0x39a1

192.168.254.7   192.168.254.7   220         0x80000169  0xd2b5

      Network Link States (Area 0.0.0.0)

Link ID         ADV Router      Age         Seq#        Checksum

192.168.1.214   192.168.254.7   220         0x80000001  0xe0f2

      AS External Link States

Link ID         ADV Router      Age         Seq#        Checksum

20.20.20.0      192.168.1.250   3           0x80000001  0x6045

20.20.21.0      192.168.1.250   3           0x80000001  0x554f

• Use the no version of the access-list command to remove the access list or the specified entry in the access list.
• Use the no version of the route-map command to remove an entry.

    baseline ip ospf

• Use to set a baseline for OSPF statistics and counters.
• The following example first displays the output of the show ip ospf command shown before you run the baseline ip ospf command; then, the execution of the baseline ip ospf command; and finally, the display of the show ip ospf command run after you execute the baseline ip ospf command.

• The output of the show ip ospf command run before the baseline ip ospf command reflects the up-to-date packet counters.
• The output of the show ip ospf delta command run after you run the baseline ip ospf command reflects the baseline set for OSPF statistics and counters.

• There is no no version.
• Example

host1#show ip ospf

Routing Process OSPF 1 with Router ID 5.106.7.1

 OSPF Statistics:

      Rcvd: 217935 total, 0 checksum errors

            8987 hello, 8367 database desc, 188 link state req

            159898 link state updates, 40484 link state acks

      Sent: 265026 total, 0 pkts dropped

            8927 hello, 8341 database desc, 53 link state req

            158571 link state updates, 89134 link state acks

 Supports only single TOS(TOS0) routes

 SPF schedule delay 0 secs, Hold time between two SPFs 3 secs

 Maximum path splits 1

 Area BACKBONE(0.0.0.0)

    Area is a transit area

    SPF algorithm executed 425 times

    ABR count 0

    ASBR count 1

    LSA Count 12

    Number of interfaces in this area is 24

    Area ranges are:

 Number of active areas in this router is 1

 1  normal, 0 stub, 0 NSSA.              

host1#baseline ip ospf

host1#show ip ospf delta

Routing Process OSPF 1 with Router ID 5.106.7.1

 OSPF Statistics:

      Rcvd: 0 total, 0 checksum errors

            0 hello, 0 database desc, 0 link state req

            0 link state updates, 0 link state acks

      Sent: 0 total, 0 pkts dropped

            0 hello, 0 database desc, 0 link state req

            0 link state updates, 0 link state acks

 Supports only single TOS(TOS0) routes

 SPF schedule delay 0 secs, Hold time between two SPFs 3 secs

 Maximum path splits 1

 Area BACKBONE(0.0.0.0)

    Area is a transit area

    SPF algorithm executed 425 times

    ABR count 0

    ASBR count 1

    LSA Count 12

    Number of interfaces in this area is 24

    Area ranges are:

 Number of active areas in this router is 1

 1  normal, 0 stub, 0 NSSA. 

    clear ip ospf redistribution

• Use to clear all the routes that have been previously redistributed into OSPF.
• Example

host1#clear ip ospf redistribution

• There is no no version.

    default-information originate

• Use to generate a default route into an OSPF routing domain.
• When you use this command to redistribute routes into an OSPF routing domain, the system automatically becomes an ASBR.
• An ASBR, however, does not, by default, generate a default route into the OSPF routing domain. The software must have a default route before it generates one, except when you have specified the always keyword.
• You can specify a metric for the route or specify that the route be OSPF external type 1 or 2.
• Example

host1(config)#router ospf 1

host1(config-router)#default-information originate 

route-map 5

• Use the no version to disable this feature.

    disable-dynamic-redistribute

• Use to halt the dynamic redistribution of routes that are initiated by changes to a route map.
• Dynamic redistribution is enabled by default.
• Example

host1(config-router)#disable-dynamic-redistribute

• Use the no version to reenable dynamic redistribution.

    distance

• Use to configure the administrative distance for OSPF routes.
• Example

host1(config-router)#distance ospf external 60

• Default settings:

• Intra-area routes - 110
• Interarea routes - 112
• External routes - 114

• Use the no version to restore the default values noted above.

    ip ospf shutdown

• Use to disable OSPF on the interface.
• Example

host1(config-if)#ip ospf shutdown

• Use the no version to enable OSPF on the interface.

    maximum-paths

• Use to control the maximum number of parallel routes that OSPF can support.
• The maximum number of routes can range from 1-16.
• The default for OSPF is 4 paths.
• To enable equal-cost multipath (ECMP) for OSPF, you need to specify a value for maxPaths greater than 1.
• Example

host1(config-router)#maximum-paths 2

• Use the no version to restore the default value, 4.

    ospf auto-cost reference-bandwidth

• Use to calculate OSPF interface cost according to bandwidth.
• Sets the OSPF metric for an interface according to the bandwidth specified.
• Affects OSPF metrics only for OSPF interfaces created after its execution.
• This command's value overrides the cost resulting from the command.
• If you want this command to apply to OSPF interfaces already configured, you need to bounce the existing interfaces: Use the no network and then the network command for the selected OSPF interfaces.
• Example

host1(config-router)#ospf auto-cost reference-bandwidth 1000

• If you issue this command, the metric is calculated as follows:

OSPF metric = bandwidth*1,000,000/link speed

For the previous example, a 64K link will get a metric of 15625, while a T1 link will have a metric of 647. The minimum value for the metric is 1.

• If you never issue the ospf auto-cost reference-bandwidth command, OSPF calculates the cost as 10⁸/link speed.
• Use the no version to assign cost based only on the interface type.

    ospf log-adjacency-changes

• Use to configure the router to send a log message when the state of an OSPF neighbor changes.
• Example

host1(config-router)#ospf log-adjacency-changes severity 3 
verbosity low

• Use the no version to halt logging of neighbor changes.

    ospf shutdown

• Use to administratively disable OSPF on the router.
• Example

host1(config-router)#ospf shutdown

• Use the no version to reenable OSPF on the interface.

    passive-interface

• Use to disable the transmission of routing updates on the interface, meaning that OSPF routing information is neither sent by nor received through the interface.
• The specified interface appears as a stub network in the OSPF domain.
• By default, OSPF is enabled on a configured OSPF interface.
• Example

host1(config-router)#passive-interface ethernet 1/0

• Use the no version to reenable the transmission of OSPF routing updates on the specified interface.

    redistribute

• Use to redistribute information from a routing domain other than OSPF into the OSPF domain.
• You can set the OSPF metric type—type 1 or type 2—and set a metric for all redistributed routes.
• Example 1

host1(config)#router ospf 5

host1(config-router)#redistribute bgp route-map 4

• If you do not specify route-map, all routes are redistributed. By default, all routes are imported as external type 2 routes.
• If you do specify route-map, but do not list any route map tags, no routes are imported.
• Use to redistribute routes from OSPF into other non-OSPF routing domains.
• Example 2

host1(config)#router bgp 100

host1(config-router)#redistribute ospf 5

• Use the no version to disable redistribution.

    table-map

• Use to apply a policy to modify distance, metric, metric type, route type, or tag values of OSPF routes about to be added to the IP routing table.
• The new route map is applied to all routes currently in and those subsequently placed in the forwarding table. Previously redistributed routes are redistributed with the changes caused by the route map.
• To remove from the forwarding table any old routes that are now disallowed by the specified route map, you must refresh the IP routing table with the clear ip routes * command.
• Example

host1(config)#route-map dist1 permit 5

host1(config-route-map)#match community boston42

host1(config-route-map)#set distance 33

host1(config-route-map)#exit

host1(config)#router ospf 100

host1(config-router)#table-map dist1

host1(config-router)#exit

host1(config)#exit

host1#clear ip routes *

• Use the no version to halt application of the route map.

    timers spf

• Use to configure the time between two consecutive SPF calculations.
• Set the time (in seconds) in the range 1-5; the default value is 3.
• If you set the hold time to 0, there is no delay between two consecutive SPF calculations. They can be done one immediately after the other.
• Example

host1(config-router)#timers spf 2

• Use the no version to return to the default value, 3.

Default Metrics

Although the system does not support a default-metric command, the redistribute command provides two ways to set a default metric for redistributed routes.

You can simply configure a metric with the redistribute command to apply to all routes redistributed from the specified source protocol:

host1(config)#router ospf 5

host1(config-router)#redistribute bgp metric 5

Alternatively, you can create one or more route maps that set the metric and apply them selectively to redistributed routes:

host1(config)#access-list 1 permit any any

host1(config)#route-map defmetric 

host1(config-route-map)#match ip address 1

host1(config-route-map)#set metric 10

host1(config-route-map)#exit

host1(config)#router ospf 5

host1(config-router)#redistribute bgp route-map defmetric

host1(config-router)#redistribute isis route-map defmetric

See Chapter 1, Configuring Routing Policy, for information on configuring route maps.