BGP anouncing with two peers.

[Martin Mares]

Hello!

> I want to setup BIRD to anounce BGP routes for my AS. 
> We have two backbone providers so I'll need to make two BGP
> connections. I only need to anounce routes and don't want to
> import them. I also want on the second BGP conection to prepend
> our AS several times, so this route should be less prefered.
> 
> I have worked out a draft bird configuratioan, but some things
> are unclear to me.
> 
> ## bird.conf ##
> protocol bgp one {
>         local as 65333; # our AS (let say it is)
>         neighbor peer.one.ip as [theiras];  # peer one and their AS
>         multihop 20 via my.next.hop.ip;   # not directly connected  
>         import none;
>         export ;      # this part is not clear to me
>                       # I want to export my whole a.b.c.d/19
>                       # network. What do I put here.
>         source address x.y.z.w; # The IP address of my router
> }

First of all, you need to have the route in your routing table to
have it exported. Usually, it's a good idea to define a sink route
for your whole address block, so that packets to non-existent
destinations in your block are not sent back and forth between
your router and your provider's router. Hence:

	protocol static {
		route 1.2.0.0/19 reject;
	}

Then you can tell the bgp's to export just this route:

	protocol bgp one {
		...
		export where net = 1.2.0.0/19;
	}

> protocol bgp one {
>         local as 65333; # our AS (let say it is)
>         neighbor peer.two.ip as [theiras];  # peer two and their AS
>         multihop 20 via my.next.hop.ip;   # not directly connected  
>         import none;
>         export ;      # Same thing as above, but prepend our AS
>                       # several times, so this route is less
>                       # prefered

Here you can use the following filter:

	export {
		if net != 1.2.0.0 then reject;
		bgp_path.prepend(1234);
		bgp_path.prepend(1234);
		bgp_path.prepend(1234);
		accept;
	};

				Have a nice fortnight
-- 
Martin `MJ' Mares   <mj at ucw.cz>   http://atrey.karlin.mff.cuni.cz/~mj/
Faculty of Math and Physics, Charles University, Prague, Czech Rep., Earth
Diplomacy is an art of saying "nice doggy" until you can find a rock.