Examine a Type 3 Summary LSA

Action

To examine a Type 3 summary LSA, enter the following CLI operational mode command:

user@host> show ospf database netsummary extensive

Sample Output

user@R2> show ospf database netsummary extensive

    OSPF link state database, area 0.0.0.0

 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 

Summary *10.0.0.1         10.0.0.2         0x80000043   529  0x2  0xfd05  28

  mask 255.255.255.255

  TOS 0x0, metric 1

  Gen timer 00:34:13

  Aging timer 00:51:10

  Installed 00:08:49 ago, expires in 00:51:11, sent 00:08:47 ago

  Ours, 

[...Output truncated...)

OSPF link state database, area 0.0.0.1

[...Output truncated...]

Summary *10.0.0.5         10.0.0.2         0x80000047  2198  0x0  0xf506  28

  mask 255.255.255.255

  TOS 0x0, metric 2

  Gen timer 00:07:19

  Aging timer 00:23:22

  Installed 00:36:38 ago, expires in 00:23:22, sent 00:36:36 ago

  Ours, 

What It Means

The sample output shows that R2 is an ABR because it contains two databases: one for the backbone area 0.0.0.0 and one for area 0.0.0.1. Within the backbone area, the summary LSA *10.0.0.1 is generated from R2 as indicated by the asterisk (*) next to the link-state ID field, and ours in the last line of the LSA. The cost to transmit data out of the interface is 1, as indicated by the metric field.

Within area 0.0.0.1, the summary LSA *10.0.0.5 is generated by R2 and has a metric of 2, which is the cost to R5 from R2. Before calculating the SPF algorithm, the local router (R2) must add an additional metric of 1 to the existing metric of 1. The additional metric of 1 must be added because there is another router between R2 and R5 (R4).

Each time the LSA is updated, the sequence (seq) field increments, indicating that the router has the most recent version of the LSA. Values range from 0x80000001 to 0x7FFFFFFF. If the sequence field is not incrementing, there may be problems with the connection.