URPF on small BGP-enabled customers?

Fri Jun 3 10:25:30 UTC 2005

I am in the process of turning up a new transit connection with SprintLink. My
network is a multi-homed stub AS and I only announce 5 prefixes. Having the bright
idea to incrementally move some traffic onto the new line I didn't announce all 5
immediately and I localpref'd ^1239$ to get some outbound traffic moving -- and the
result is of course that they drop any of my outbound traffic sourced from prefixes
I'm not announcing yet. This really smells like URPF but of course nobody at Sprint
has even confirmed that they are actually dropping packets.

This is new to me, but I haven't bought any new transit in the past 18 months -- is
this common practice on multihomed BGP customers now? I could force things to work
by always advertising all my prefixes out to them with the obvious downside of
living in fear of my outbound traffic being dropped if I ever need to withdraw any
of them.

If they're paranoid enough to manually filter my BGP announcements it's not much
more work to manually filter my source addresses too (nevermind the fact that I
already do it myself, but...)

I'm working through the SprintLink noc/support process but I'm surprised this
hasn't happened to any of their other customers before now.

Am I missing something obvious here?

-- 
-Will  :: AD6XL
 Orton :: http://www.loopfree.net/