Subject: relationship of RD/VRF/VPN

From: Peng Li <[email-masked]>
Date: Sat, 2 Jun 2001 15:49:12 -0700

Hi,
   In the RFC2547, it seemed to define that each VPN will have its unique
router distinguisher value.  In CISCO PRESS book, "MPLS and VPN
Architecture", 2nd printing, page 172 also expressed the same idea.
However, in cisco routers, each VRF with associated with one or multiple
interface can participate in multiple VPNs, (e.g. the case where one CE
routers participate in multiple VPNs).  And each VRF will have a RD
associated with it.  Thus, a RD is not one-to-one mapping relationship with
VPN anymore.   Anyone else confused by this? Can someone please explain to
me what is the correct relationship of RD/VRF and VPN?

many thanks,
peng

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From: Senthilkumar Rajasekharan <[email-masked]>
Date: Sun, 3 Jun 2001 21:11:14 -0400 (EDT)

Hi,

> VPN anymore.   

True. RD and a VPN do not have a one-to-one association in all cases
although its possible to have a VPN that has a one-to-one
mapping with an RD value.

>Anyone else confused by this? Can someone please explain to me 
>what is the correct relationship of RD/VRF and VPN?

RD values map to a VRF and a VPN can be a grouping of multiple VRFs. And 
so the RD values have a one-to-one mapping with a VRF and the VRF has a
many-to-one mapping with a VPN in the Intranets case and many-to-many
relationship in the Extranets case ( by virtue of extending RT values of a
VRF).

Hope this Helps,
-Senthil

P:S > I have refrained from going into vendor specific issues and I can
answer vendor specific questions either offline or you can post a query to
[email-masked]