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Webcast-Catalyst9k
New Member

BGP - Missing Routes

Hi,

OSPF and BGP running on the MPLS Router.

OSPF for LAN

BGP with Service Provider

I am redistributing ospf to BGP and also

redistributing BGP to OSPF

some routes from OSPF cannot be seen on BGP neighbors

HQ====service_Provider=======Branch(1)

At HQ when we do

sh ip route ospf, I see route

172.35.20.0

on Branch (1)

This route is not seen

Any clue

4 REPLIES
Cisco Employee

Re: BGP - Missing Routes

Hello,

I assume you want to see the network 172.35.20.0/24 on the Branch router.

1.) Check if the network 172.35.20.0 has been properly redistributed from OSPF to BGP on the HQ site by issuing the command show ip bgp and looking for that network. Verify that the BGP reports this route as valid and best in your BGP table. Also, by issuing the command show ip bgp 172.35.20.0/24 make sure that it was announced to your ISP's router: look for the number of the update-group in that command's output and then checking who is a member of that update group by entering show ip bgp update-group

2.) Skip this step if you are running eBGP with your ISP. Otherwise, if you are running iBGP to your ISP, verify what is the next hop address attribute of the network 172.35.20.0/24 in your BGP table. If it is not 0.0.0.0 then it might be possible that the ISP does not know the route to that next hop. In this case, using "next-hop-self" in the BGP neighbor configuration might help.

3.) Assuming that the route has been announced to your ISP with a reachable next hop (you can verify this also by debugging the BGP), the ISP should have received that route from you. On the Branch, verify the BGP table by show ip bgp. If the network 172.35.20.0 is not there, you will probably need to discuss this with your ISP. If it is there but did not make it into your routing table, try to verify if its next hop is reachable.

Also, debugging the BGP on the Branch site might provide useful output - perhaps the AS_PATH already contains the AS number of the Branch site and the router rejects it, or there may be another hint as to what is the problem.

Best regards,

Peter

New Member

Re: BGP - Missing Routes

Thank You for the reply.

At HQ when I do

show ip bgp 172.35.20.0/24

network not in table.

All Branches network are seen at HQ via (*>)

172.35.20.0/24 network is learnt via ospf at HQ and this network is not directly connected at HQ.

Instead of getting all routes I need to filter Networks from HQ to branch

192.168.100.0/24

192.168.200.0/24

172.35.20.0/24

172.17.20.0/24

networks from branch to HQ

10.10.10.0/24

Cisco Employee

Re: BGP - Missing Routes

Hello,

Your description is somewhat confusing - I am struggling to understand where is the network 172.35.20.0/24 located.

For now, I assume that it is somewhere on the HQ site and it is being announced by OSPF.

Now, you have said that this network is not in the show ip bgp output on the HQ. Do you see it in your routing table on the HQ at all? It should be present as an OSPF route. If it is present in the routing table but not in the BGP table then it should only be a problem of redistributing that network into BGP. In that case, double-check your redistribution configuration.

Best regards,

Peter

Re: BGP - Missing Routes

is the 172.35.20.0 in the HQ side?

can you do the follwoing command on the HQ router

show ip bgp nei X.X.X.X avertised-routes

where x.x.x.x is the ISP next hope router to you HQ router

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