[c-nsp] BGP Upstream in different interfaces.

[Philip Smith]

Alexandra Alvarado said the following on 14/02/2005 17:11:
> 
> I have three ISP Provider for backup, and via BGP I have been configured
> three network group each one preferred for each provider and as backup for
> the others (adding as-path prepend), it works well for download  but for
> upstream all the traffic only goes for one preferred interface (local
> preference 120).

Setting local pref high on one interface will generally make that 
interface prefered for outbound traffic.

> I would like to know if is possible to choose the upstream traffic by
> selected networks without applying "service policy" in the interface but by
> BGP in the neighbors?

Of course. But it depends on what you hear from your upstreams. If all 
three give you the full Internet routing table, removing the local-pref 
120 will give you some semblence of outbound load balancing (which is a 
start but will need to be worked on depending on each provider's 
relative AS path length to the "centre of the internet"). If all three 
give you just the default route, you might need to review this so that 
at least two give you some part of the routing table so you can 
loadbalance outbound. Check out the NANOG 32 Multihoming tutorial for 
ideas: ftp://ftp-eng.cisco.com/pfs/seminars/NANOG32-BGP-Multihoming.pdf.

philip
--