iBGP and redundancy problem.

[Jeroen Massar]

> On 18 May 2026, at 09:21, Mike Neo <neomikemac at gmail.com> wrote:
> 
> I think there's a problem with knowing how to access clients/internet via iBGP. When the ISP on R1 goes down, I can't even access the internet from R1 via iBGP. Perhaps there's some routing missing in this area.

I would suggest providing configuration and routing table excerpts if you want anybody on the list to help you out.

Regards,
 Jeroen


> 
> niedz., 17 maj 2026 o 23:43 Jeroen Massar <jeroen at massar.ch> napisał(a):
> 
> 
> > On 17 May 2026, at 20:44, Mike Neo <neomikemac at gmail.com> wrote:
> > 
> > Are you BGP exchanging routes between R1 and R2?
> > Yes.
> > 
> > Does R1 pull/removes the routes from the upstream when they are down.
> > Yes.
> > 
> > Are R2 routes visible, likely less preferred, on R1?
> > Yes, via iBGP.
> 
> Then, what is the post-failover state that apparently fails?
> Check routing tables on R1 and R2, both bird and the kernel routing tables.
> 
> Also do a traceroute from a client to see where things go, or if possible log in to each and use similar to 'ip ro get <remote-ip>' to see where the next hop leads. But also be sure to do that all the way from R2.
> 
> Does R2 how to get to R1 to get to the clients?
> 
> 
> And just in case, if NAT or even normal connection tracking is involved that might cause issues primarily due to the missing state on R2 where those packets are not expected.
> 
> Also this is all assuming that both R1 and R2 are announcing the same prefixes and that upstream keeps on sending packets.
> 
> Regars,
>  Jeroen
>