North American Network Operators Group

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Re: multi homing pressure

  • From: Jon Lewis
  • Date: Wed Oct 19 23:19:07 2005

On Wed, 19 Oct 2005, Owen DeLong wrote:

I've done simple ASN/BGP based multihoming for a number of businesses, and,
it can be done on a mostly set-and-forget basis.  If you have your upstreams
supply via BGP and no other routes, and, you advertise your
networks, believe it or not, that's a pretty stable configuration.  If
your upstreams are reasonably reliable, that works pretty well.  If not,
and, you care about knowing what your upstreams can't reach at the moment,
then, you need a full feed and life becomes slightly more complicated.
There's really nothing more complicated about taking 2 (or more) full views, other than keeping an eye on available memory. The C&W/PSI incident a few years ago and the more recent Cogent/Level3 incident are perfect examples of why taking two 0/0's really doesn't cut it if you want reliable connectivity to the "whole internet".

Cisco burned a lot people by building routers with needlessly limited RAM capacities (planned obsolescence?). Because of that, one customer wouldn't buy another cisco, and instead went Imagestream. They have 3 full views and no worries now. They were so happy with that Imagestream, they ended up buying a bunch more for internal WAN needs.

Another customer I dealt with recently was fairly typical of the "small multihomer" I'd guess. They were multihomed to two Tier1 providers and wanted to replace one of them with us. Their BGP had been done either by a consultant or former employee and was definitely set and forgot on autopilot. Their router (cisco 3640) kept "dying" and they'd just power cycle it as needed. When I got in to take a look, I found it was taking full views and had pretty much no RAM left...and it was announcing all their space deaggregated as /24s for no reason. They weren't willing to shell out the $ for a bigger router, so I ended up configuring them for full routes from us and customer routes from their other (a Tier1) provider (and fixing their advertisements). Other than expansion (more network statements), running out of RAM again, or changing providers, I doubt their BGP config will need to be touched in the forseeable future.

Jon Lewis | I route
Senior Network Engineer | therefore you are
Atlantic Net | _________ for PGP public key_________