Creating OSPF Stub Network

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May 29th, 2008
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I have attached a net. diagram showing a basic OSPF design, with a single stub network. Routers A, B, C, D are all in ospf area 0 (router C is a L3 3550). My question is with setting up router (E) as a stub network of area 0. I have customers behind router (E) that need to be able to reach the internet as well as other portions of network. I want this to be stub area 1

My questions are how can I setup this, keep OSPF running between router (C) and (E). Since this is a stub network, do I need a default route on the router (E)? Or will dynamic routing still take place?

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Kevin Dorrell Thu, 05/29/2008 - 23:04
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The thing to remember here is that OSPF does not put routers into areas, but networks. This seems a fine distinction, but is actually quite important here. You should also remember that OSPF does not have stub networks, it has stub areas.

So, on all your routers, put the links of that ABCD loop into area 0. On router D, put the link into area 1; network area 1. Then do area 1 stub. Router D becomes a border router between your stub area 1 and the backbone.

Router E end of that link should also be in area 1, and area 1 declared as stub. If you want area 1 to contain only the default route, then router D should have area 1 stub no-summary. It will then inject a default route into the area 1, which router E will pick up. The "no-summary" is only necessary on the area border router (D).

Kevin Dorrell



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