[quagga-users 11053] BGP Route Preference

Jason Timmins jason at interlinx.co.uk
Fri Aug 28 09:24:45 IST 2009

Hi Fellas,

I work for a small hosting company in the UK. We have our own AS and PI IP
address allocation and take BGP Internet feeds from three transit providers. We
use Quagga on Linux boxes to provide our BGP and OSPF infrastructure.

Quagga has been fantastic. We've been using it for a couple of years and it's
performed faultlessly. Thanks for creating such a terrific set of software. We
wouldn't have been able to do any of the cool stuff we do without Quagga and
your efforts. Thanks.

As I mentioned, we take BGP feeds from three transit providers. One of them is
significantly cheaper than the others and we'd like to use their connectivity in
preference to the others. I know that this is viewed in two parts, choosing
which connection we use to send our packets (is relatively simple) and
specifying which connection we'd prefer to receive packets on (a bit more

I'd like to know how to do both of these things but the outbound preference

Using bgpd, how do I say "If the number of AS hops is the same, send my packets
out via my preferred supplier." At the moment, we take full BGP feeds from the
three providers and let bgpd decide where the packets go but I'd like to
influence that decision a little bit. I've looked in the docs but I can't see
what I need to do.

I understand that inbound traffic can be influenced by artificially pre-pending
our own AS number on to the routes we send to our non-preferred transit
providers. Essentially, this makes us seem 'further away' via those guys so the
traffic will tend to come in via our preferred provider. Have I got that right?
How's it done?

Thanks guys.

Bye for now

Jason Timmins (Technical Director) InterLinx Ltd.
 Geo: West Mids, UK. Tele: +44 1902 896511. Fax: +44 1902 324748.
                Beyond here there be dragons!

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