[c-nsp] Redundant default route, without round-robin routing

[Oliver Boehmer (oboehmer)]

Vincent De Keyzer <> wrote on Thursday, September 27, 2007 3:25 PM:

> Hello list,
> 
> I would like your ideas to complete my design.
> 
> This is an ISP network. All 10 routers in the city are interconnected
> on a /27 subnet, over which everybody has a full OSPF adjacency with
> the DR and the BDR.
> 
> Two of those routers are BGP-connected to the upstream providers (one
> each). The other routers are access routers, and cannot hold a full
> BGP table; they hence need a default route.
> 
> I was thinking of having both BGP routers advertising a default route
> in OSPF; but in this case, in order to limit packet out-of-sequence
> problems, I want to make sure that every IP flow uses the same
> default gateway. 
> 
> Is there a way to ensure that? Or should I proceed differently at
> routing level (how) ?

This is the default operation, so unless you configured CEF per-packet,
you will not see out-of-order packets. Make sure to mesh the two eBGP
speakers via iBGP. Guess you want to disable icmp redirects on the
interface, best link those two eBGP speakers with a dedicated link to
prevent blackholes..

	oli