[c-nsp] is RPF strict mode common?

[Justin M. Streiner]

On Thu, 8 May 2008, Adam Greene wrote:

> The obvious solution to me will be to prepend my route announcements to 
> Global Crossing. However, one question: there is a good chance that some 
> of my traffic will flow out through Savvis and in through Global 
> Crossing (in fact, that's almost certainly happening right now). Will 
> this kind of asymmetrical traffic run into issues with other ISPs that 
> deploy RPF in strict mode? Are there many ISPs out there that do this?

While it's certainly a plausible scenario, an ISP that runs strict RPF on 
multihomed customer links is begging for trouble for exactly the reasons 
you described.  The might run loose RPF, or straight ingress/egress 
filtering, which should be OK.  Strict RPF is meant for singlehomed sites.

Bottom line, you should be able to alter your edge routing policies in the 
ways you described to make better utilization of your transit links 
without too much fear of breaking things in interesting ways...

jms