Hi
Well it is hard to say where is a problem without the configuration. Don't you swap import/export statements? For example, kernel protocol should have 'export filter { if net = 0.0.0.0/0 then reject; accept};' if you do not want to export default route to it.
Or you could just have default reject/unreachable route, like in this example:
This example worked perfectly for me. Thanks. My problem was, that I didn't really understand how to originate the default route at the border router which performs OSPF and BGP. Normally a border Router doesn't have a default-route in its' routing table. Cisco originated the default-route via "default information originate". That's what I wanted to configure. But as I wrote before: the example worked perfectly.
My 2nd desire is the following: A{1,2} should throw the default-route in the OSPF area <only> if the BGP adjacency is reachable and the BGP peer is formed (BGP state should be established). Is this desire realizable with bird only?
No, that is not possible. Unless you convince your ISPs to send you also a default route through the BGP and use it to redistribute it to OSPF.
But it is not a big problem - the router with BGP session down already has external routes from IBGP, so the traffic will be directed to the other border router.
This is the normal case. But we want to build a network design which isn't, well...., as normal as others. That's why I was asking if it was possible with bird only. Thanks, Ondrej.