[127157] in North American Network Operators' Group
Re: BGP Multihoming Partial vs. Full Routes
daemon@ATHENA.MIT.EDU (Anton Kapela)
Tue Jun 15 23:20:52 2010
From: Anton Kapela <tkapela@gmail.com>
In-Reply-To: <8CFFB682-FD8A-4E42-8A67-EB68C67B8F8B@cisco.com>
Date: Tue, 15 Jun 2010 20:20:20 -0700
To: Fred Baker <fred@cisco.com>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Jun 14, 2010, at 12:08 PM, Fred Baker wrote:
> upstream, full routes are generally not as useful as one might expect. =
You're at least as well off with default routes for your upstreams plus =
what we call "Optimized Edge Routing", which allows you to identify =
(dynamically, for each prefix/peer you care about) which of your various =
ISPs gives you a route that *you* would prefer in terms of reachability =
and RTT. In the words of a prominent hardware store in my region, "you =
can do it, we can help".
+1.
additionally, one could filter on reasonable RIR allocation 'boundaries' =
per /8, cutting the fib down substantially. Cisco and a host of others =
maintain such a list of ready-to-use examples here:
=
ftp://ftp-eng.cisco.com/cons/isp/security/Ingress-Prefix-Filter-Templates/=
lastly, one could do something far more crude (yet strangely =
effective), like so:
ip prefix-list longs permit 0.0.0.0/0 ge 23
ip prefix-list shorts permit 0.0.0.0/0 le 22
ip as-path access-list 10 permit =
(^_[0-9]+$|^_[0-9]+_[0-9]+$|^_[0-9]+_[0-9]+_[0-9]+$)
route-map provider-in permit 10
match ip address prefix-list longs
match as-path 10
route-map provider-in permit 20
match ip address prefix-list shorts
...etc
-Tk=
