Resilience - How many BGP providers

Dylan Ebner dylan.ebner at
Wed Nov 11 11:27:23 CST 2009

You question has many caveats. Just having two providers does not necessarily get you more resiliency. If you have two providers and they are terminating on the same router, then you still have a SPOF problem. You also need to look at pysical paths as well. If you have two (or three) providers and they are using a common carrier, then you have a problem as well. For example, GLBX has a small prescence in the Minneapolis metro. If I were to use them as a provider, they would use Qwest as a last mile. If my other provider is Qwest (which it is), I may not have path divergence.
Facilities are important too. We have three upstreams; Qwest, MCI and ATT. The facility only has two entrances, so that means two of these are in the same conduit. IF you only have one entrance, all you connections are going to run through that conduit, and that makes you susceptable to a rouge backhoe.

You are on the right track to question your resilancy. Some upstreams can offer good resilancy with multiple feeds. Others cannot. I would start with your provider and see what you are getting. Maybe you already have path divergence, sperate last miles, and multiple paths in the isp core.  If you go with multiple providers, you want to make sure you don't risk losing something you already have.

-----Original Message-----
From: adel at [mailto:adel at] 
Sent: Wednesday, November 11, 2009 11:14 AM
To: nanog at
Subject: Resilience - How many BGP providers



After recent discussions on the list, I've been thinking about the affects
of multiple BGP feeds to the overall resilience of Internet connectivity
for my organisation.  So originally when I looked at the design
proposals, there was a provision in there for four connections with the
same Internet provider.  Thinking about it and with the valuable input of
members on this list, it was obvious that multiple connections from the
same provider defeated the aim of providing resilience. 

So having come to the decision to use two providers and BGP peer with
both, I'm wondering how much more resilience I would get by peering
with more than two providers.  So will it significantly increase my
resilience by peering with three providers for example, as both of the
upstreams I choose will be multihomed to other providers.  Especially as
I am only looking at peering out of the UK. 

Hope the above makes sense. 


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