mpls multiple P routers in same AS

Unanswered Question
Jun 24th, 2008

hi freinds

first im a newbie for MPLS.

I have a simple network , as follows

CE-PE1-P1-P2-PE2-CE.

I have a problem with this scenario that CE to CE is not reachable.

Int he same network If there is only one P router then it's working fine.

Can anyone suggest?

Ps:

1.BGP neighbor is fine and routes are reveived at both PE routers.

2.MPLS and CEF enabled on all Provider devices.

3.one suspect is , when there are 2 P routers PE1 router is advertising my

PE2's loopback (where it's peering in BGP) to P1.and P1 do not have any labels ( untagged)

pls help

I have this problem too.
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a.alekseev Tue, 06/24/2008 - 00:55

You should run some IGP protocol (IS-IS, OSPF, EIGRP) between PE1-P1-P2-PE2.

shivlu jain Tue, 06/24/2008 - 02:14

rajiv

i would like to tell you that the number of P routers has nothing to do with the prefixes. You should have to check are the labels are generating and you are getting the mpls ldp up or not. If possible please paste the configuration that will be better for us to find out the problem.

regards

shivlu

rajivrajan1 Tue, 06/24/2008 - 04:14

hi friends,

first , thanks a lot for reply.I will post the configs 2mrow.

I am running ospf as a IGP- my PE routers are receving VRF routes.

My PE1 is advertising the Neighbour loopback IP (Other end PE2 IGP peer) to it's LDP neighbor (P1). SO P1 is saying untagged for that particular destination, when i chk show mpls ldp bindings.

Is this fine ?

rajivrajan1 Tue, 06/24/2008 - 22:04

hi friends

I have found the problem.It was an accesslist which was controlling the LDP advertisements from P1 to PE1.Fixed and found working.

Thanx for reply and help - rated you both ;)

thanx bye

tarjbains Fri, 06/27/2008 - 14:00

CE-PE1-p1-p2-PE2-CE

hi friends i have one problem as well

i want to implement ISP backbone network with MPLS into PE1-PE2 core. in core network PE an P routers running OSPF. at edge router running EBGP PE1,PE2 with other ISP two sides and i want to connect internal them with IBGP. for this normally we use Route reflector or confederation. but for more scalability if i want to remove IBGP peering from core P1,P2 just OSPF protocol and IBGP on Edge routers PE1-PE2 and label will run for IBGP in transit router.no routing of IBGP will store on P core routers. Is it possible. plz reply

mohammedmahmoud Sat, 06/28/2008 - 02:05

Hi Tarj,

First of all, i'd recommend you to start a new thread in case you have your own problem to solve, unless your problem is related to the original post.

As for you question, what you have described is the exact behavior of a service provider with a MPLS backbone, it is a BGP free core, the P routers need not run BGP, since the PE routers will have LSP tunnels using label switching over the backbone and the P routers will just do label swapping and not IP lookups, accordingly the P routers needs not learn the BGP routes, but however you need all the routers (PEs and Ps) to run an IGP in order to be able to build the forwarding plane tables.

I hope that i've been informative.

BR,

Mohammed Mahmoud.

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