change RD

Unanswered Question
Mar 31st, 2008

during inter-as communication can we use the different RD values for the same customer.

for example in ist sp vrf is test and rd is 1:1 and the same vrf is made in second sp with differenr rd. can they communicate or not.



I have this problem too.
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vasiliev1984 Mon, 03/31/2008 - 09:36

In this situation you can use different solution. If it's new connection between different MPLS network you can use two variant.

Your situation it's very often in the VPNv4 prefix exchange with MP-BGP implementation.

About RD, RD using by VRF import process to import routing information to the isolated VRF instance. Take a look, this sample (knows as «route leaking»):

ip vrf test

route-target import 1:1

route-target import 1:2

route-target export 1:1

Ok we have one vrf (it's name test) and two different RD value, first it's 1:1 and second it's 1:2. ISP to define for this vrf RD 1:1, but this client should be need another service from another vpn (like VoIP… it does not matter).

First we import all routing update information and routers from MP-BGP, this operation operate by VRF-import process, this process knows from what RD import and install routes. As result from this configuration we can see at routing table for this vpn, many different routes from one VRF (VPN) and another VRF (VPN). But you should be controlling in this situation address space between different vpn's (for this situation you can controlling import process with route-map).

Information about route leaking, you can find here -

Another solutions it's rewrite RD value in the MP-BGP updates. About this solution and how can configure at Cisco IOS, you can find here -

And finally you can use "inter-vrf connect" best practice without VPNv4 NLRI MP-BGP exchange.. You can configure logical sub-interface or using Tunnel's interface to connect between PE routers different ISP with our Layer 2 domain. (Like one VLAN ID between trunk or access physical connection between different PE routers and place this interface with needed vrf instance).

PS: I think you can use this three solution's: route leaking, RD rewrite and inter-vrf connect. That your solutions? I don't know it's your chouse...

Harold Ritter Mon, 03/31/2008 - 12:04


the RD is prepended to the ipv4 routes so that the same ipv4 route coming from two different VRFs will be seen as different VPNv4 routes. The import/export process uses the route-target extended community.


vasiliev1984 Mon, 03/31/2008 - 14:33

Yes, you are right. It's my mistake. RD need to be prepend IPv4 prefix and make him to globally unique. RT need to identify VPN at site, because RD can not identify VPN. Sorry my head it's not working now, today I have many work :)

Harold Ritter Mon, 03/31/2008 - 11:48


You certainly can. Even within the scope of the same AS, different RDs from one PE to another are sometimes configured for load-balancing purposes.

Global connectivity will be controlled by the route-target extended communities. So as long as you have the proper RT export and import statement configured at both ends, everything should be just fine.


shivlu jain Wed, 04/02/2008 - 09:05

thanks to all for your valuable time and inputs. Now i have one more query can we use LDP between asbr-1-sp1 and asbr-2-pe2 means ldp between inter as.

Also one more query can we make the vpn lable unique in inter-as.




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