MPLS in parallel

[Earl Granger IV]

Hi community,

I am looking for the best solution for migrating to a new MPLS provider.  I am running a 7200 router with vrf's configured and it has our current provider that supplies internet and mpls.  How do I add the new mpls provider at the same time and cut each remote location over to the new MPLS.  Should I add another router in the mix for the new provider or do I connect the circuit into my current router?

Thanks guys!

[milan.kulik]

Hi,

I'd say it depends on your topology and number of sites but I guess you will need to peer to both MPLS providers for some time?

So you will probably need to start peering to the new provider on your central router (is there only one?).

And to advertise the subnets of the migrated remote sites to the old MPLS network (and vice versa) to keep the connectivity between the migrated sites and those still connected to the old provider.

In that case you need to check the AS numbers used by both providers to avoid any clashes.

Worst case you will need to configure some static routes on your central router or some routing protocol redistribution to handle the clashing AS numbers.

Best regards,

Milan

[Earl Granger IV]

I believe there are roughly 50 sites out there.  For now there is only one router.  We would be keeping our ASN on our side. However, its not as easy as creating another vrf and OSPF instance for redistributing into the core?  Let me know

Thanks

[Jon Marshall]

Earl

Why do you have VRFs on your 7200 ? ie. usually the CE device (which i am assuming it is) does not have any VRFs.

That aside the last time i did a large migration like this (from an ATM to MPLS network) we used two routers and then used the core behind to route between the existing and new networks. You can do it all on one router but we found it easier because we could bring up the new link, get everything working between us and the provider without having to do any new configuration on our existing router. Basically if we messed up with the new connection it had very little impact on the existing network.

It also made it a lot easier to isolate any issues as the routing tables etc. were a lot easier to manage/interpret if we were having issues.

That said we had the budget to purchase a new router and you may not so, as Milan says, it could be done on the same router. How you would do that depends on your current configuration which is why i asked about VRFs.

Jon

[Earl Granger IV]

Yes we have vrfs on the router.  We have a vrf for a company that we merged with.  VRF for Internet and one is for the MPLS.  I was thinking about adding an additional router for the new circuit.  I could justify it saying that we could have a router that has not been modified and if we need to fallback to it we can with no issues.

[Jon Marshall]

Earl

Okay, that makes more sense.

I think if you can i would use another router for exactly the reasons you describe. It just makes everythiing a lot easier (in my opinion) and minimises the risk of any new configuration affecting your exsiting network.

Once it is migrated then you can migrate the other VRFs across or just keep the two routers running together.

Jon

[milan.kulik]

I'd need to know more details about your curremnt network.

So far I supposed you were using BGP as the routing protocol between your CE routers and the MPLS provider PEs?

Where is OSPF involved exactly?

Best regards,

Milan

[Earl Granger IV]

There is an ospf instance for internet 2 routers and ASA and BGP redistribution into that area.   Then there is a instance for the core area 0 ospf that the core switches and the mpls vrf is participating in.  MPLS bgp prefixes are being mutually redisdistributed into ospf.