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Community Member

Routing specific VRF traffic over the MPLS backbone link

Hi All,

We are trying to use a specific backbone link in the MPLS to be used only by the specific VRF traffic and not rest all. Is there a way to achive this? Is Traffic engineering would be an answer,if so, can suggest a brief not on how to deploy.

Thanks

Regards

Anantha Subramanian Natarajan

9 REPLIES

Re: Routing specific VRF traffic over the MPLS backbone link

Anantha, you can achieve this by having a MPLS TE tunnels created on the path you want and then have a forwarding adjacency for that vrf only through that tunnel.

Create additional loopbacks per vrf ( in global table) on either side and manipulate the BGP nexthop to point to that new loopback, instead of regular loopback 0.

For eg:

1) Create loopback 1 in global for vrf1 on the egress PE. On the Ingress use a global static loopback 1 route pointing to the tunnel which terminates on this egress PE.

Manipulate the nex-hop in the MPBGP update on the ingress using import map pointing to the loopback 1 on the egress.

Or

2) Assign the BGP next-hop to be used for that VRF as loopback 1 in vrf config mode.

HTH-Cheers,

Swaroop

Community Member

Re: Routing specific VRF traffic over the MPLS backbone link

Hi Swaroop,

Thank you very much. Please correct my understanding,if wrong...By above method, we would be able to force particular VRF(s) traffic through the tunnel created over the link, can we stop other VRF traffic using the backbone link over which we have created the tunnel.

We would like to find an solution, where an particular MPLS backbone link would be used only for certain VRF traffic and not by others.Infact to the core of the requirement, we are trying to use a particular backbone link only for the data traffic and not for voice traffic. In our network,since we differentiated the data and voice traffic over seperate VRF for the customer, we now looking for data VRF is the one should be using that particular backbone link and not voice.

Kindly let me know

Thanks

Regards

Anantha Subramanian Natarajan

Re: Routing specific VRF traffic over the MPLS backbone link

Anantha,

if you have couple of PE's and many links out of which you want to choose and pick, then it would be a good idea to have a full mesh TE topology.

And setup up the tunnels using explicit method. So for every PE they would be 2 tunnels for each destination, one the Voice tunnel and second the Data tunnel. Both setup using explicit method. Voice Tunnels would be carrying only Voice VRF traffic as you would have modified the next hop for the voice vrf as reachable through the voice tunnel. And for the data VRF's you do not do any manipualtion they go by the remote PE nexthop via the preset data tunnel by default.

HTH-Cheers,

Swaroop

Community Member

Re: Routing specific VRF traffic over the MPLS backbone link

Hi Swaroop,

Thank you very much

Regards

Anantha Subramanian Natarajan

Community Member

Re: Routing specific VRF traffic over the MPLS backbone link

Hi Swaroop,

I have a doubt/question,Is it possible to achieve the above scenario by creating manual tunnel and using explicit path to the concerned link and assigning the reserved bandwidth on the tunnel equal to the link b/w,in which case, only eplicitly routed traffic on this tunnel would be able to travel that link and general traffic wouldn't be able to use this link because the TE tunnel already reserved the Max b/w of the link.

Is the above understanding right ???

Kindly let me know

Thanks for the help.

Regards

Anantha Subramanian Natarajan

Cisco Employee

Re: Routing specific VRF traffic over the MPLS backbone link

Hi,

Just as a sidenote: the same principle - per VRF BGP next hops - can be applied without MPLS TE. You then need to tweak your IGP metric for a given Loopback prefix to the desired path or use static routing to achieve the same.

It is your design choice, if the different challenges presented by both approaches are worth it and which solution better fits your needs.

Regards, Martin

Community Member

Re: Routing specific VRF traffic over the MPLS backbone link

Hi Martin,

Thanks.....Will try that also.....

In addition to this, Swaroop or Martin,can we able to map a tunnel traffic with respect to QOS bits(DSCP or IP or EXP).......

Thanks

Regards

Anantha Subramanian Natarajan

Re: Routing specific VRF traffic over the MPLS backbone link

Anantha, to answer your previous question, you can use RSVP based reservation but your IGP routing wont be influenced by RSVP reservations on a link. which means that the data traffic which you want

to avoid certain links as per IGP that link may still be the best path for them. But although you can assign all such links which data traffic should avoid a higher metric, and configure rsvp with control of all the bandwdith on the link,

so it can allocate till the available bw on the link. This way IGP routing would not select that link and only RSVP would which means your TE tunnels for voice would use that link.

To answer your second one, yes you can map EXP (COS,PREC,DSCP) to a TE tunnel here is a reference link for the same.

http://www.cisco.com/en/US/products/sw/iosswrel/ps1829/products_feature_guide09186a00802659b9.html

If you are working on a enterprise network implementing MPLS backbone and data and voice vrf's are the only kind of services

then you can plan to forward traffic on the TE tunnels based on the EXP without the nexthop manipulation. Or else if you want granular control

manipualting the next hop would make sense. Its purely based upon your reqs.

HTH-Cheers,

Swaroop

Community Member

Re: Routing specific VRF traffic over the MPLS backbone link

Hi Swaroop,

Great.....Thank you very much

For me it looks the BGP next-hop solution suggested by you and martin would be appropriate but would also like to know the TE solution ,so that our engineering group would be able to decide a solution based on long run.

Once again thanks

Regards

Anantha Subramanian Natarajan

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