From: Michelle T (mtruman@xxxxxxxxxxxxxxx)
Date: Thu Dec 21 2000 - 22:03:48 GMT-3
Kevin,
They are referring to Intra-AS, not Inter-AS. Think of the IGP that runs
under the covers of all large ISP's today. It is there to provide granular
next-hop interface metrics. So BPG (internal) runs Backbone/Core router to
router and next hops are recursively looked up via OSPF (in our case).In
addition to the IGP, most if not all run confederations, route reflectors,
or both to avoid a full mesh. Now imagine all the internal routers running
MPLS instead, with Label switch paths. Each router basically has a route and
a forwarding interface associated with it in the VRF table. With MPLS (and
there are to be MPLS extensions to BGP if there are not already), the bgp
route will be mapped to a label switched path or tagged as it were. I
believe you still need an IGP, but you sure don't need route reflectors. I
don't fully understand it, but basically, the core looks like a bunch of L2
devices to BGP (Like ATM switches), the BGP peer across the core looks like
it's directly connected at Layer 3.
There are Inter-AS MPLS negotiations underway however.
Michelle
----- Original Message -----
From: "Kevin Gannon" <kevin@gannons.net>
To: "groupstudy" <ccielab@groupstudy.com>
Sent: Thursday, December 21, 2000 6:26 PM
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 Consultant
>
> kevin@gannons.net
> ----------------------------------------------------------
>
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