Examine a Type 1 Router LSA

Action

To examine a Type 1 router LSA, enter the following CLI operational mode command:

user@host> show ospf database router extensive

Sample Output

user@R1> show ospf database router extensive 

    OSPF link state database, area 0.0.0.1

 Type       ID               Adv Rtr           Seq      Age  Opt  Cksum  Len 

Router  *10.0.0.1         10.0.0.1         0x8000005a  1180  0x0  0x5828  60

  bits 0x2, link count 3

  id 10.0.0.1, data 255.255.255.255, Type Stub (3)

  TOS count 0, TOS 0 metric 0

  id 10.0.0.2, data 10.1.12.1, Type PointToPoint (1)

  TOS count 0, TOS 0 metric 1

  id 10.1.12.0, data 255.255.255.252, Type Stub (3)

  TOS count 0, TOS 0 metric 1

  Gen timer 00:30:19

  Aging timer 00:40:19

  Installed 00:19:40 ago, expires in 00:40:20, sent 00:19:38 ago

  Ours

Router   10.0.0.2         10.0.0.2         0x8000004b   679  0x0  0xe6c0  48

  bits 0x3, link count 2

  id 10.0.0.1, data 10.1.12.2, Type PointToPoint (1)

  TOS count 0, TOS 0 metric 1

  id 10.1.12.0, data 255.255.255.252, Type Stub (3)

  TOS count 0, TOS 0 metric 1

  Aging timer 00:48:40

  Installed 00:11:16 ago, expires in 00:48:41, sent 3w0d 23:33:12 ago

What It Means

The sample output shows the details of two router LSAs: the first for R1 (*10.0.0.1) and the second for R2 (10.0.0.2). The asterisk (*) indicates that the LSA was generated by R1. You can also determine ownership of the LSA by the last line of the output in this case, ours.

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.

The bits field is set to 0x2 in the first LSA and 0x3 in the second LSA. When the bits field is set to 0x2,the originating router (R1) is an ASBR. When the bits field is set to 0x3, the originating router (R2) is both ABR and ASBR.

R1 has three links connected to area 0.0.0.1 shown by the link count field that is set to a value of 3. The Type field shows that R1 has a single point-to-point link to R2 and two links advertised as stub networks.

Each OSPF router generates a single Type 1 LSA to describe the status and cost (metric) of all links on the router. This LSA is flooded to each router in the OSPF area. It is defined as having an area scope, so it is not flooded across an area boundary.