Static route aggregation for BGP announcement
Anand Buddhdev
arb at anand.org
Thu Aug 11 22:16:41 CEST 2005
Hi everyone,
I've recently setup bird 1.0.11 on a Linux system. I've defined my
static routes likes this:
protocol static {
route x.y.z.0/27 via "eth3";
route x.y.z+1.0/24 via "eth2";
route x.y.z+2.0/24 via "eth2";
route x.y.z+5.0/25 via "eth2";
route x.y.z+5.128/26 via "eth2";
route x.y.z+5.192/28 via "eth2";
route x.y.z.0/20 drop;
}
I have a /20 allocation from the RIPE NCC, which is x.y.z.0/20
I have configured my BGP as follows:
protocol bgp {
local as MYASN;
neighbor a.b.c.d as REMOTE-AS;
path metric 1; # Prefer routes with shorter paths (like Cisco)
source address e.f.g.h; # local address TCP connection
export where source=RTS_STATIC;
import all;
}
This works, and I see x.y.z.0/20 advertised, if I look through a looking
glass router. However, what I am not clear about is this: does bird
actually export _all_ the static routes I have defined? And are they
simply not visible because my upstream is filtering them? Or is bird
actually clever enough to see that x.y.z.0/20 is an aggregate of all the
other routes, and only advertises the one route?
And what do other users recommend? Is my setup ok, or is it better if I
change the export line to actually export only the one prefix?
Regards,
Anand
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