[c-nsp] IGP & iBGP Configuration Problem in Transit AS

[Vira W]

Hi Cisco gurus,


I have a network topology in this URL :
http://www.4freeimagehost.com/show.php?i=3f0ac19164c9.png

 My first problem is in IGP configuration inside AS 100. I'm using OSPF. I
still confused how to make non-BGP router (C,E,B,D) understand how route the
packet transitting this AS. I have tried default route advertisement via
OSPF, but since AS 100 is multihomed, there still any chance looping is
happened there. How to configure it properly, without redistributing BGP
route into OSPF.

Second, I understand that iBGP inside AS 100 needs to be configured in mesh
topology. Otherwise, use route reflector or confederation. But, if I use
route reflector, I'm confused because the each route reflector itself must
be meshed, in the other side, from the physical topology (as in the
picture), there is none router that is connected mesh. So, which router
should I choose as RR. Then, if I choose BGP confederation, still inside
sub-AS the router must be connected in mesh topology, which impossible from
the topology.

So guys, what is your suggestion for my problem in IGP and iBGP
configuration inside AS 100?
I've read many books about BGP, particularly about transit AS, but their
examples is always simple networks. I have found none complex case study
network similar my topology.

Thanks a lot. Every your comment, suggestion, criticism, will be very much
appreciated.