Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
New Member

internal networks unreachable if iBGP neighbor wan goes down

Hello,

I have 2 Nexus 5000's as iBGP neighbors, both have their own wan access, if wan goes down on one of the nexus, I loose access to internal networks even from neighbor router with active wan, I can only ping physical interfaces on the nexus.

I have attache BGP config for reference.

thanks

7 REPLIES
New Member

internal networks unreachable if iBGP neighbor wan goes down

Hi,

Can you post the output of 'show ip bgp' when both WAN interfaces are up and when one of the WAN interfaces is down?

Thanks,

New Member

Re: internal networks unreachable if iBGP neighbor wan goes down

Thank you for your response, I don't have sh ip bgp when circuit is down, I have attached current with both circuits up.

regards

New Member

Re: internal networks unreachable if iBGP neighbor wan goes down

Hi,


Thanks for these.

I can see in the show ip bgp outputs that the ibgp path to all destinations is using the next-hop address of the opposite N5ks WAN connection. For example dist-1 is using next-hop address 10.50.132.18 which is the WAN connection for dist-2. For BGP to consider a path valid, the router must be able to route to the advertised next-hop addess.

Can you check if dist-1 has a route for 10.50.132.18 this address in its local RIB?

The normal way to resolve this issue is to set 'next-hop-self' for the iBGP connection on both N5ks or advertise the WAN next hop addresses into IGP.

I can see in the BGP configuation that an iBGP peer-policy has been configured with next-hop-self but it doesnt appear to be applied.

New Member

Re: internal networks unreachable if iBGP neighbor wan goes down

I am new to Nexus, how to apply ? I thought adding in configuration will do it .

thanks

New Member

Re: internal networks unreachable if iBGP neighbor wan goes down

Hi,

I would just configure next-hop-self for each neighbor as follows

dist-1

neighbor 10.25.38.12 remote-as 64415

    description << iBGP Peering to DIST2 >>

    update-source loopback0

    address-family ipv4 unicast

      next-hop-self

dist-2

neighbor 10.25.38.11 remote-as 64415

    description << iBGP Peering to DIST1 >>

    update-source loopback0

    address-family ipv4 unicast

      next-hop-self

New Member

Re: internal networks unreachable if iBGP neighbor wan goes down

This is how it's configured on dist1, I thought I have to do a committ, will schedule a windiow & test if internal routes are reachable.

Thanks again for all your help, will update with result.

New Member

Re: internal networks unreachable if iBGP neighbor wan goes down

Hi Will,

I applied next-hop-self to both ibgp neighbors, still same issue. In sh ip bgp default route from dist2 is advertised to dist1 as you mentioned, no change.

thanks

257
Views
0
Helpful
7
Replies
CreatePlease to create content