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A single LAN with several switches and computers exist within a single VLAN behind each router. There are no more routers behind the ones describe on the image. OSPF Area 0 already exists. Router CBA already exists with static routes. LM and RH are new routers (sites) added to the network. IG site holds the main computer center. Router RH will provide communications for RH site computers and will become a disaster recovery site with a replica of servers from IG. Router LM will provide communications for LM site computers and a redundant link for RH and IG.

I need to add LM, RH and CBA to the OSPF "cloud"

What will be the advantage if I define OSPF Area X as part of area 0? Is it better to define Area X with a different area number? Why? How should I add CBA to the OSPF cloud? As part of area 0? as a separate area? as part of area X? If Area X is define as a different area, Will there be any advantage if Area X is define as a stub area? Why? Do you have any other recommendations before adding those routers to the OSPF domain?

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up vote 2 down vote accepted

RH and LM shouldn't be in Area 0 as they both have to pass through IG to get to it, so, they don't need to know Area 0's network topology.

Make RH and LM Area 1, stub IG's router interface in Area 1.

CBA would be Area 2 with IG's router interface stubbed into Area 2.

Reminds me of one of the diagrams from the CCNE test.

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Thanks, can you please expand a little further the idea of the stub setup. I can not still grasp the whole concept. By the way this is a real scenario so it seems that this experience will help me with tests in the future. :-) – 3D1L Sep 12 '10 at 19:02

If RH is the disaster recovery site should IG be unavailable, how does it route to Area 0 (CCTV1, CCTV2, IC) or CBA? You need to add some redundant routes.

For "IG be unavailable," from a disaster recovery standpoint, don't think in terms of a router down. Think in terms of building fire, all of downtown flooded, etc.

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mpez0 that's exactly my concern but since IG is acting as the main "hub" (single point of failure), I was wondering about the need to forward routing information between areas. Something that I can not still understand completely. But with your help I will ;-) – 3D1L Sep 12 '10 at 19:06
IG can pass routing information as well as packets as long as it's up and running. If it's down hard, though, it is the single point of failure that means RH cannot communicate with Area 0. – mpez0 Sep 17 '10 at 23:31

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