[c-nsp] asymmetric multihoming & nat

[Pete Lumbis]

NAT could definitely be causing issues. Generally you could use
something like Stateful NAT (SNAT) between the two BGP speakers to
make sure they sync their NAT tables, but this this feature has had a
number of challenges/issues and development and started moving it to
end of life.



On Fri, Jan 21, 2011 at 4:09 PM, Adam Greene <maillist at webjogger.net> wrote:
> Hi guys,
>
> I have a multihomed customer who receives full BGP routes from both us and
> another provider and load balances between the two connections. Things are
> working fine until the traffic becomes asymmetric (i.e. inbound through one
> provider, outbound through the other).
>
> The block they are announcing to their providers is NATed on their BGP
> router. In other words, all their internal hosts are on private IP space.
> The internal interface is designated "ip nat inside" and both WAN interfaces
> are designated "ip nat outside". The actual NAT configurations do not
> reference any interfaces, just pools.
>
> Could the NAT be prohibiting asymmetric traffic in this case? i.e. if the
> inbound traffic is NATed coming in on one interface, will the router refuse
> to NAT the outbound traffic through the other interface?
>
> If the NAT is the problem, I suppose they could do the NAT on a loopback
> interface instead ... but I understand that the traffic will all be
> process-switched if we do that, and performance will probably suffer.
>
> Thanks for your insight,
> Adam
>
> _______________________________________________
> cisco-nsp mailing list  cisco-nsp at puck.nether.net
> https://puck.nether.net/mailman/listinfo/cisco-nsp
> archive at http://puck.nether.net/pipermail/cisco-nsp/
>