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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