The MPLS-OPS Archive

[Ajay Simha <asimha@cisco.com>]

On Mon, 20 May 2002, Christopher Poh wrote:

>CP:Hi again,
>CP:
>CP:Thank you for clarifying about BGP peering. What about if an interior
>CP:router (non-BGP peer) would want to establish a connection to exterior
>CP:routes? Would the LSPs for those routes be available to the interior
>CP:router?


Via IGP? Would there be some label distribution protocol running between this
new non-BGP peer and the internal router? If so yes. If not no.

-ajay

>CP:
>CP:
>CP:5/20/02 1:01:47 PM, Rajiv Asati <rajiva@cisco.com> wrote:
>CP:
>CP:>Christopher,
>CP:>
>CP:>In a MPLS network, an ASBR, which is learning ipv4 routes via an eBGP
>CP:>neighbor, typically doesn't allocate/advertise any label for those ipv4
>CP:>routes that are advertised to its iBGP neighbors.
>CP:>
>CP:>         <-------AS#1-------->        <-----AS#2.--->
>CP:>         R1-------R2--------R3--------------P1---------------P2
>CP:>                 |
>CP:>                 R4
>CP:>
>CP:>So in the above topology, R3 may be learning 10,000 ipv4 routes from P1
>CP:>(which is an eBGP neighbor) and may advertise those 10,000 ipv4 routes to
>CP:>R1 and R4 (R3's iBGP neighbors). From R1 and R4 perspective, R3 is the
>CP:>next-hop for all those 10,000 routes. So, R1 will have a label to reach R3
>CP:>and it will use that single label to reach all those 10,000 routes.
>CP:>Similarly, R4 will also have a label to reach R3 and that label will also
>CP:>be applied to any of those 10,000 prefixes.
>CP:>
>CP:>As far as peering to all the internal routes are concerned, MPLS provides
>CP:>the ability to make core routers BGP free. In other words, R2 above doesn't
>CP:>need to be an iBGP neighbor and so it doesn't need to know about 10,000
>CP:>prefixes.
>CP:>
>CP:>Please let me know if I could be of more help.
>CP:>
>CP:>Rajiv
>CP:>
>CP:>At 09:13 PM 5/19/2002, Christopher Poh wrote:
>CP:>>Hi,
>CP:>>
>CP:>>How does an AS border router advertise and make known to all other routers
>CP:>>within a domain about label/FEC binding information for every exterior
>CP:>>routes it
>CP:>>carry? Does the router need to peer with all the interior routers in order
>CP:>>to distribute this information?
>CP:>>
>CP:>>Hope someone could help me with this.
>CP:
>CP:
>CP:
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