Bird and aggregates

[Joel Brunenberg]

Hi Hans, Hi List,

thank you for your clarification,

On Thu, Apr 16, 2015 at 06:27:30PM +0200, Hans van Kranenburg wrote:
> Hi,
> 
> On 16/04/15 16:43, Joel Brunenberg wrote:
> >[...]
> >
> >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.
> 
> Yes, I would suggest using a static blackhole route with the large aggregate
> range for the BGP connection, and also export that to your local kernel
> routing table to automatically drop traffic for all addresses that are
> currently not in use.

It seems I concentrated so much on the aspect of making the appearance
of the route conditional that I missed the obvious point. What you say
makes total sense.

> Is there a special reason why you would want to have the /24 being removed
> entirely if none of the other connections is up?

I would like to retract the route in the case, no contributing routes
are there so traffic is no longer attracted in that case. If that is not
possible, a static blackhole route would be ok, too I guess.

So its correct to assume that the following things would do?

 * in protocol static add a blackhole route for the aggregate network
 * export the aggregate route to the kernel
 * export the aggregate route to be BGP peers with next-hop self
 * NO NOT export the aggreage to the OSPF areas
 * Be happy and dance around the table

I will have a try and see if it works. If there was a way to
conditionally import a specific protocol or filter on the presence of
specific prefixes in the RIB that would be awesome.

Thank you so far,

 Joel

/jbn

-- 
Joel Brunenberg - Troisdorf
PGP: 0xAD25981C
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