Route availability Problem in MPLS

Unanswered Question
Aug 30th, 2007

Hi,

I have taken an MPLS connectivity between two offices and would like to deploy backup Leased Line connectivity through other ISP.

I have configured static route for both the links.

MPLS with High priority and Leased Line with slightly lower value.

In the event of MPLS local /remote (local loop) failure the traffic is not switching over to the Secondary backup Link.

I need to explicitly shutdown the MPLS interface at my branch for routing the traffic through Leased Line.

The interface on the other side is not able to sense the link failure at the primary site.

(This is an IP MPLS).

Kindly suggest of what configuration should be effected so that my requirement will get addressed.

Regards

Ravi

I have this problem too.
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Mohamed Sobair Thu, 08/30/2007 - 11:07

Hi Ravi,

As I understand from your post, you are a customer & have being provided with an MPLS connectivity service through specific Service provider. 2nd thing, you have a nother link through different Service provider as backup.

If I am right, then technically you router is a CE (Customer edge) and shouldnt be MPLS aware, the MPLS Only run within the SP MPLS cloud.

3rd, you are running static-route with your service provider edge, this should take care of the failure of any route issue, whatever type of routing protocol you use with your SP, it should take care about any physical link failure. If it doesnt, its possible that you router didnt detect any failure with the Next-Hop address (SP router address).

It could be the SP router is reachable via your router , but at the same time he is facing some problems within his cloud.

I mean may be the failur within the SP Network Cloud.

As from technical point of view, the Stati-route should be removed from the routing table if the next-hop address is not reachable, and your second floating static- route should take over.

Kindly check with them if they can help & provide you with further details.

Regards,

Mohamed Sobair

cwy Fri, 08/31/2007 - 21:03

Maybe the router don't know the remote end connection lost, so the static route still in the routing table. I think one of the solution is you can apply BGP or other routing protocol to let both ends routers to learn the routes.

HTH!

Andy

imuonagor Mon, 09/03/2007 - 05:29

We're having the same problem in our network. We have subscribed to a service provider's mpls vpn and we also have backup links for our branches. We configurs EIGRP to automatically switch links in events of failure of either one. The eigrp peering uses the mpls ethernet interface while the backup link uses GRE tunnel. However when the mpls link goes down, the router doesn't switch to the backup. We can verify that the mpls vpn link is down as we are unable to ping the mpls ethernet interface from our HQ whereas we can ping the interface for the backup. We log in to the branch Router through the backup link (which is up but not being used) and when we do a sh ip route it's still showing the mpls vpn as the eigrp route to HQ learnt from the PE router. We then have to shut down the mpls vpn link interface on our branch router to have the router start using the backup link. Is there any reason why the mpls vpn's PE router keep advertising to the branch Router that it still has a route to HQ even when the mpls vpn link is down? How could we resolve this? Thanks for your assistance.

Mohamed Sobair Tue, 09/04/2007 - 22:45

Hi guys,

a routing protocol will definetely solve his problem, but this must be agreed with his service provider.

while you are using a static route as CE-PE , on the two branches, when a failure occurs on one side, the other side didnt detect the failure & still beleives your MPLS Network is your primary path.

But, if you run a dynamic routing protocol between CE-PE on both sides & being carried through MP-BGP at the service provider, failure on one link is detectable at other branch since its dynamic.

Agreement with the service provider about specific routing protocol is manadatory & would solve this issue.

Regards,

Mohamed Sobair

imuonagor Tue, 09/04/2007 - 23:15

Hi Mohamed,

I don't know about Ravi's case but in my client's case we use eigrp between CE and PE.

But the PE keeps advertising to the CE (via eigrp) that it has a valid route to the HQ even when the mpls link is down.

We have to log in to the branch router via the backup link and shutdown the mpls interface before eigrp will failover to the backup link. Please assist further.

Thanks...

Ifeanyi

ravichandrantg@... Tue, 09/04/2007 - 23:59

Hi,

Yes talking to Solution provider for routing protocol is an option.

But the best solution i feel is to create a Tunnel across both the routers for the MPLS Link and then run a routing protocol.

I did the same in my environment.

Regards

Ravi.

Mohamed Sobair Wed, 09/05/2007 - 00:16

Hi feanyi,

This shouldnt happen, If you are running eigrp as CE-PE routing protociol on both sides it should detect any route failure.

I just wanna ask you, HOW THE PE Keeps advertising to the CE that it has a route to the HQ?? meaning the PE is getting an eigrp routes from Other PE through MP-BGP, that means your routing protocol is working fine as well at other site..

I actually confused how one PE could receive a (vrf - eigrp) routes pointing to the HQ while there is a routing issue on the other site????

This is very confusing..

could u please explain further what is your current setup , configuration wise.

Regards,

Mohamed Sobair

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