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Question about BGP/MPLS VPNs with NHS disabled

  • From: Gargi Nalawade <gargi@cisco.com>
  • Date: Sat, 12 Jul 2003 09:46:31 -0700
  • CC: mpls@UU.NET, Arun Pasupathy <apasupathy@opnet.com>


Pe-2 need not have NHS in order to set itself as the nexthop. The PE-CE
session is eBGP & so the PE will always set tself as the nexthop.

-Gargi

Sachin Kalra wrote:
> 
> Dear MPLS Community:
> 
> I would appreciate if someone can answer the following question about
> BGP-MPLS VPNs.
> 
> Lets say we have the following topology:
> 
> [CE1]                                                              [CE11]
>          \                                                            /
>           [PE1]-----------------[Rtr1]-------------------[PE2]
>          /                                                            \
> [CE2]                                                             [CE22]
> 
> 1. Running IBGP between PE1 and PE2.
> 2. Running EBGP between all PEs and CEs.
> 3. BGP "Next Hop Self (NHS)" option is disabled on PEs.
> 
> Now, when PE1 receive a route from PE2, how will PE1 know "BGP Next Hop"
> address for that route? As NHS is disabled on PE2, the new route will have
> CE's address as "BGP Next Hop", and PE1 will not be able to find any LSP
> going to that CE.
> 
> Is this correct?
> 
> I appreciate your response.
> Thanks,
> Sachin Kalra