OSPF area

Unanswered Question
Feb 17th, 2007


I have two catalyst L3 switches.

L2 trunk and HSRP is configured among them.

if we put these two switches in different OSPF area provided both the swithes directly connected backbone area 0.

do we have to put interfaces which running running HSRP in same area or we can put diffrent area without any issues?

I am scratching my head to know abt this



I have this problem too.
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Richard Burts Sat, 02/17/2007 - 07:58


It is not clear to me what the topology of your network is. You describe only two L3 switches and we do not know if there is more to the network than that. We also are not clear whether some VLANs are only on one switch or whether all VLANs are shared by both switches. And with only two switches I am not clear why you need OSPF.

But one thing about OSPF is clear. For switch ports in the same VLAN, they must be in the same OSPF area. A VLAN is a subnet and OSPF routers in the same subnet must be in the same area. If they are in different areas then they will not become neighbors and will not share routing information with each other.



rajeshk200_2 Sat, 02/17/2007 - 09:08


Thanks for the response.

We have got two datacenters and each datacenter has got dual core and dual distribution switches.

All four(2+2) switches are interconnected with L2 trunk and having same vlan info across all distribution switches.

HSRP is configured between all 4 distribution for each vlan.

Each distribution switch has got L3 interconnect with core switch in the same datacenter.

Now both the datacenter switches are in same OSPF area and we are in the process of putting into two diffrent area.

my question is can we put distribution swithes in datacenter A in area 1 and datacenter B distribution swithes in area 2 and all core uplink interfaces in area 0?




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