Re: MPLS VPN Route Target Rewrite

Hi Carlos,
Thank you very much for this well explained description of this process. I
can see crystal clear now what is going on.

The thing that I didn't wasn't seeing is that the RD is applied before the
export map and that the MP-BGP is one table for all VRFs.

Thank you again for helping me understand this!!!

Tom

On Tue, Feb 1, 2011 at 7:00 AM, Carlos G Mendioroz <tron_at_huapi.ba.ar> wrote:

> Tom,
> just to easy things for you, and not to leave a mess in the list archives!
>
> First, as I don't have the topology, what I believe it is:
> (please use a monospaced type like courier for the ASCII "art")
>
>
> VPN_A(100:1) VPN_A(100:1)
> | <100:55*
> 172.16.7.0/24 (S) | 100:55> 172.16.5.0/24
> 155.1.67.0/24 (C) <100:1> | <100:1> 150.1.58.0/24
> |
> [R6] --MP-BGP-- [R5]
> |
> 150.1.76/0/24 <100:2> | <100:2> 150.1.5.0/24
> 192.168.7.0/24 <100:55 |
> |
> VPN_B(100:2) VPN_B(100:2)
>
>
> How to read: R5 and R6 habe a MP-BGP adjacency and have both VPN_A
> (upper networks) and VPN_B (lower networks) VRFs.
> In the midle, <100:X> are RTs, with signs showing import or export
> direction into vpnv4 "bag" of routes. The one with an asterisk is
> controlled by an export map. Inside parenthesis are RDs.
>
> If this diagram is wrong, the following is wrong too! (GIGO principle :)
>
> Now, your "interesting" route was 172.16.5.0/24.
> This is local to R5 in vrf VPN_A.
>
> Because it matches the export map, it is tagged with RT 100:55 and
> because it originates at R5's VPN_A VRF, it gets RD 100:1.
>
> Goes to R6 via MP-BGP.
>
> It is imported by VPN_B VRF (because of RT 100:55) into vpnv4 (RD 100:2)
> and unicast vrf VPN_B.
>
> So you see the route twice at vpnv4, one with RD 100:1 (default for
> VPN_A_at_R6 but really the RD of VPN_A_at_R5) and one with RD:100:2 (via
> VPN_B_at_R6).
>
> Notice that even though the RD corresponds to that of VPN_A_at_R6, the
> route only has RT 100:55, and that is not being imported by VPN_A_at_R6.
>
> Hope this is clear.
> -Carlos
>
>
> --
> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina

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Received on Sat Feb 12 2011 - 11:37:08 ART