From: Rob Webber (rwebber@xxxxxxxxxxxx)
Date: Fri Dec 22 2000 - 12:28:11 GMT-3
I'll add my two cents...the edge routers still maintain a full iBGP mesh
among themselves (possibly using route reflectors or confeds, it doesn't
matter). So any routes learned by any edge router get propagated to all
other edge routers. This allows every edge router will know about all
routes.
Since the core routers don't directly learn about any external routes (they
typically don't connect to customers or upstream ISPs) they don't need to be
part of the BGP process. So the core routers don't participate in BGP (and
thus the BGP full mash).
Without MPLS core routers need BGP because if an edge router forwards a
packet to the core, the core routers must know about all 90,000 Internet
routes (via BGP) so that they will know where to forward the packet. However
with MPLS the core routers are only forwarding based on MPLS tags - not
actual destination IP addresses (as is the case without MPLS).
Does that make sense?
Rob.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Kevin Gannon
Sent: Thursday, December 21, 2000 7:26 PM
To: groupstudy
Subject: MPLS Removes the need for core BGP tables ??
I am reading the new Cisco MPLS book and they state that you can use MPLS
to remove the need for you to have a full BGP mesh within your core routers
to achieve transit. Can someone please explain how this actually works
I have been racking my brains with no luck.
I can understand that you can use a tag pair for the next hop address
of your upstream peers instead of a tag pair for the actual route. But
this still doesnt explain how a remote pop will know network 123/8 is
reachable across the core via POP X.
Regards,
Kevin
-- ---------------------------------------------------------- Kevin Gannon CCNP,CCDP,MCNS,Cisco Netranger Engineer,HP Openview Consultantkevin@gannons.net ----------------------------------------------------------
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