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

[Mark Tinka]

On Monday 16 June 2008, Vira W wrote:

>  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.

Well, if the routers can't talk BGP, then, as others have 
mentioned, some of your options are tunnels or label 
switching (MPLS).

> Second, I understand that iBGP inside AS 100 needs to be
> configured in mesh topology.

Right - part of the BGP spec.

> Otherwise, use route 
> reflector or confederation.

I wouldn't recommend confederations - personally, I think 
they are complex and unnecessary (unless you've inherited a 
legacy setup).

Route reflectors are the way to go.

> 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.

Since you have an IGP running within AS100, IP reachability 
between the route reflectors will be available, and they 
can mesh.

> So, which router should I 
> choose as RR.

The only other routers, you say, that can do BGP are A, F, G 
and H.

You could choose any two (I'm unsure about the actual 
dynamics of your network to make a decision for you), and 
they should work, because OSPF will figure out how 
to "connect" them.

> Then, if I choose BGP confederation,...

Step away from the confederation :-).

Hope this helps.

Cheers,

Mark.
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