OSPF area plan

[deepak george]

Dear All,

I have an existing network setup, ISP1 connecting to the MPLS cloud that connects to other branch offices. ISP2 to connect to the outside world. I only have area 50 in my network and area 0 is at ISP1 end that is the MPLS cloud.I do not have info about ISP 2 's area 0.

I would like to upgrade my network by using Nexus 5k's to connect to my servers . Also would like to run L3 between VSS Core and the N5k's.

My question is how do i plan my OSPF design and to which area do i assign the new server farm to?(N5k's to the core VSS)

Do i create a new area or use existing area 50?

Do i create a totally stub as i am trying to minimize the LSA updates.

Do i create new area 0 in my LAN network as it does not have Area 0 , but has got it only on ISP1's MPLS cloud.

Or else is there a new plan?

Please note that all my static routes from other branches in the MPLS cloud are redistributed into OSPF as this is the hub site and all the spokes will have to go through this Core VSS to reach outside.

I am attaching the topology for reference.

B1,B2,B3 are the branches where the MPLS clouds connect to.

Thanks in advance

[Jon Marshall]

If you are peering with ISP1 using OSPF which it sounds like you are then you definitely don't want to create another area 0 in your LAN.

And if you created a new area that area also would need connectivity to area 0 and not via area 50 unless you configured a virtual link between area 50 and your ISP router

However in general you should only use virtual links when you have to and the ISP would have to get involved if you wanted to configure it. So I would recommend against that as it complicates things significantly with very little gain.

All you are really doing is connecting a pair of switches to your existing infrastructure and i can't really see the need to do anything other than add them to your existing area.

I understand what you mean about the switches receiving all the LSAs for remote sites but i wouldn't have thought that would be a problem for Nexus switches.

If it really was a concern then you say you are proposing to connect the switches with L3 to the VSS switches. If that was the case you could always configure routed ports with IPs and if needed configure default routes on the Nexus switches pointing to the VSS switches and configure static routes for the server subnets on the VSS switches pointing to the Nexus switches.

Whichever you use i would make it as simple as possible so definitely no need for another area as far as i can see.

Jon

[deepak george]

Hi Jon,

Thanks for getting back with your views on the same. I have another question here, if i have 2 Nexus 5k's connected to each other by a vPC peer link, the Nexus 5k's connecting to the Core VSS(4500),and run OSPF between them using the routed interfaces. Would the OSPF traffic between n5k1 and n5k2 be dropped as i believe that no other traffic should pass across vPC peer link ,they would be dropped. 

I am attaching a diagram here for better understanding.

Thanks for your support as always.