[c-nsp] Prefer (outbound) certain bgp peer for AS or subnet ?

Nick Hilliard nick at foobar.org
Tue Oct 15 05:40:08 EDT 2013

On 15/10/2013 05:17, CiscoNSP List wrote:
> What is the best method to prefer upstream B egress (For AS or  /24)?

Asymmetric routing is a normal part of internet operations.  It's not clear
why your clients are complaining, but if it's purely because the traffic is
routed asymmetrically (rather than because of performance problems on the
outbound / return paths), they need gentle application of a cluebat.

If you want to prefer a specific uplink based on a source address or ASN,
then you need to use policy based routing.  This is probably a real bad
idea for all the usual reasons.  On the other hand, if there are good
performance reasons to select a specific egress path for one customer, then
probably there are good reasons to use that path for all your other
customers too.  In this case you might want to put in a policy rule to bump
your metrics based on an upstream community or prefix list or as path,
depending on how granular you want things to be and how much RP CPU you're
prepared to sacrifice on the problem.


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