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New Member

OSPF Design Question

Gents need some advice.

At work we are in the middle of a massive project which includes  building two new datacentres and redesigning our campus.  I'm looking  after the design for the campus network and need some advice.

So the campus will be OSPF area 176 and the datacenters area 0.

There are two Cisco 3560E switches installed as the core of the campus  network.  There are linked via two 10Gb links and configured in an  etherchannel.  The two datacentres connect to these two switches as  well.

So my question is about the etherchannel link between the two core  switches.  See the diagram in the link below, area 0 and area 176 will potentially  need to traverse this link if there is ever a break in on of the primary  paths.

So the discussions we have had at work is around the routing configuring of the core switch interconnect.  Should it be:

a) A routed  etherchannel (no switchport command) with the etherchannel in area 0
b) A routed etherchannel (no switchport command) with the etherchannel in area 176
c) A layer 2 trunk etherchannel, using two VLAN interfaces on each end used for routing.  So there would be for example,
interface vlan 100 in area 0 on both switches
interface vlan 200 in area 176 on both switches.

The concensus at work is that C is the way to go, but i just wanted other options as to the pros and cons of each option...


Cisco Employee

Re: OSPF Design Question

Are you doing any summarization for the Campus Area?


New Member

Re: OSPF Design Question

yes a summary address for the campus will be advertsied outside of area 176.

Same goes for the datacentres.

Cisco Employee

Re: OSPF Design Question

If the topology is exactly as you have shown in the figure (with no extra links / devices) then just using the core to core interconnect configured as a Layer-3 point-to-point interface part of Area 0 should suffice. If, however, there can be potential situations where a switch will continue to advertise a summary while one of the local interconnects has failed then you are better off with going with option 3 (have a logical interconnect in both Area 0 and 176).


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