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Routes in RT, but not in OSPF database

x_plana01
Beginner
Beginner

Hi folks,

I recently noticed OSPF behavior, which I don´t understad - routes are in routing table, but I don´t see them in OSPF database.

s100_unl_vtp#sh ip route 10.100.254.1
Routing entry for 10.100.254.1/32
  Known via "ospf 100", distance 110, metric 2, type intra area
  Last update from 10.100.248.1 on Vlan1000, 2w3d ago
  Routing Descriptor Blocks:
  * 10.100.248.1, from 10.251.254.100, 2w3d ago, via Vlan1000
      Route metric is 2, traffic share count is 1

s100_unl_vtp#sh ip ospf database | i 10.100.254.1
s100_unl_vtp#

router ospf 100
log-adjacency-changes
area 100 nssa
redistribute static subnets
network 10.100.0.0 0.0.255.255 area 100

Basically I don´t see most of LSA from this router´s "own" area I would expect  - there should be a lot of type 2 LSAs from end user LANs, but there are none. Everything is working fine, I am just confused, as routing table should be just the best routes picked from OSPF database, right?

Thanks,

Martin

1 Accepted Solution

Accepted Solutions

Peter Paluch
Hall of Fame Cisco Employee Hall of Fame Cisco Employee
Hall of Fame Cisco Employee

Hi Martin,

The OSPF database is not a plain database of reachable networks but rather a database of topological compontents out of which the shortest paths are extracted by a shortest path algorithm. Because of that, you should not expect to see a network to be just visible in the show ip ospf database output, rather, you have to look at the originating router's LSA to see if it is indicated there.

For your particular query, you want to look at the LSA1 of the originating router 10.251.254.100 to see if there is a record about a network 10.100.254.1/32. Try to issue the command

show ip ospf database router adv-router 10.251.254.100

I believe you will find the network 10.100.254.1/32 in the output (marked as a stub network).

Best regards,

Peter

View solution in original post

2 Replies 2

Peter Paluch
Hall of Fame Cisco Employee Hall of Fame Cisco Employee
Hall of Fame Cisco Employee

Hi Martin,

The OSPF database is not a plain database of reachable networks but rather a database of topological compontents out of which the shortest paths are extracted by a shortest path algorithm. Because of that, you should not expect to see a network to be just visible in the show ip ospf database output, rather, you have to look at the originating router's LSA to see if it is indicated there.

For your particular query, you want to look at the LSA1 of the originating router 10.251.254.100 to see if there is a record about a network 10.100.254.1/32. Try to issue the command

show ip ospf database router adv-router 10.251.254.100

I believe you will find the network 10.100.254.1/32 in the output (marked as a stub network).

Best regards,

Peter

Hi Peter,

thanks for answer. So I understand it wrong, the network is indeed present there.

Have a nice day!

Martin

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