OSPF area 0 issues

[dhughes133]

HI

I after some help.

I have the topology set up in the attached diagram which has been working fine Site 2 has been learning the routes from Site 1 due the cost added to interface vlan on 812. When Site NSSA goes down Site 1 learns the routes from Site 2. Happy days. How ever very recently for some unknown reason. Site 2 doesn't learn anything from site 1 anymore. I have neighbors formed for area 0 and for area 811 and 812. 

If I drop area 811 on site 1, site 1 learns the routes from Site 2. If I drop area 812 on site, site 2 learns nothing from site 1. I've cleared the process on both sites, even removed and re added the config as a last ditch attempt to get this working but nothing. Its a very simple setup that has been working perfectly.

Can anyone please shed any light on the situation.

Cheers

Diagram is attached

[lespejel]

Hello @dhughes133

hard to say just looking at the diagram since you haven't shown any LSA.

There's a loop prevention mechanism used to prevent loops with routes coming out from MPLS provider, can't say if that's your case without evidence, but try with ospf capability vrf-lite under the OSPF process.

Also, please check this document Why Are Some OSPF Routes in the Database but Not in the Routing Table? and if you still have the issue, please share an example: show ip ospf database external x.x.x.x so we can see if the LSA for the desired route is present, how it was generated and why is not in the routing table?

show ip ospf database external x.x.x.x

show ip ospf database router [id for the router injecting the LSA]

show ip ospf database asbr-summary 

show ip ospf database nssa-external 

[dhughes133]

Hi

The routes are being populated into each OSPF NSSA area on each individual site. If i take out NSSA on site 1 routes from site 2 populate the routing table. If I take out NSSA area on site 2 no routes from Site 1 appear in the routing table. This has been working and no changes to the configuration or network have occurred. In normal operation I see N1 routes on Site 1 and E1 routes on site two. I take out NSSA on site 1 and site one has E1 routes and Site 2 has N1 routes and visa versa. Its a weird one.

[paul driver]

Hello

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@dhughes133 wrote:

HI

I after some help.

I have the topology set up in the attached diagram which has been working fine Site 2 has been learning the routes from Site 1 due the cost added to interface vlan on 812. When Site NSSA goes down Site 1 learns the routes from Site 2. Happy days. How ever very recently for some unknown reason. Site 2 doesn't learn anything from site 1 anymore. I have neighbors formed for area 0 and for area 811 and 812.  

Are you aware of any changes over this period anything even if you think might not have affected this resiliency. 

Can you post the:
sh run |  section router
sh ip ospf route

[dhughes133]

Hi Paul,

Its a weird one mate. See above message. I've attached the requested from both sites.

Cheers

[dhughes133 · Accepted solution]

HI everyone,

Sussed out what was going on. There was prefix-list being used for route filtering which didn't have a permit any at the bottom so was blocking all routes.

Thanks everyone