Re: BGP as an IGP (Was Re: IGPs in use)

["Sean M. Doran" <smd () clock org>]

Chrisy Luke wrote:

| Paul G. Donner wrote (on Oct 13):
| > If BGP rides on TCP, how are the TCP sessions built if BGP itself is used
| > as the IGP?
|
| Same way as it does when you take next-hops from any other IGP. The fact
| that one already has a route to ones' directly attached networks.

In other words, the interior routing protocol is either static
or a combination of statically configured routes and the likes
of ARP/ES-IS/other neighbour discovery protocols.

The key point is that, in a router talking iBGP, the route to the
NEXT_HOP received by an iBGP neighbour *MUST* be known through
means other than BGP.  This is not to say that the route need
be dynamic -- a static default route would do just fine.

        Sean.