Bird and aggregates

Joel Brunenberg ml at jjim.de
Thu Apr 16 16:43:21 CEST 2015


Hi bird list,

I am thinking about this for some time now, reading documentation and
all but I did not find a solution until now, so I am turining to you:

Does bird (1.4.5) support aggregate routes in any way? The Scenario is
as follows. I have a VPN consisting of around 20-40 ptp-links, an OSPF
area that spans these links and several larger subnets that are
connected to the nodes that interconnect using the named ptp links.

So far so good. I would not want to interfere with the Prefixes in the
OSPF. I however have a BGP-session to another network and I am exporting
most of my routes to that session. I'd like to replace all the /32
routes for ptp links with the /24 they are taken from while exporting
routes for that BGP session.

Since it is totally irrelevant for the peer, which parts of the /24 are
available, I would just like to attract traffic to the networks I manage
as long as there are any contributing routes.

I had several ideas on how to do that, one being an export filter that
replaces every /32 with the according /24, but that would lead to a lot
of /24 routes and seems to be impossible with bird since the prefix
attribute is immutable.

Another idea was a static route for the containing /24 that would be
exported via BGP while the /32 were filtered away. That however leaves
the /24 route in place even if there are no more /32 routes left. If
there is a way to change that, that would be great.

If anyone has any idea how to accomplish this, it would be very much
appreciated.

Thanks in advance,

 Joel

/jbn

-- 
Joel Brunenberg - Troisdorf
PGP: 0xAD25981C
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