[c-nsp] OSPF area design question

James Hampton james.hampton at gmail.com
Mon Aug 30 15:47:50 EDT 2004


The way I'm reading this is that you have three hub routers connected
like  points on a triangle, with each point having 15 or so spokes? If
this is the case I would make the top router(or the one in the middle)
area 0 and the others 1 and 2 or what ever numbering scheme you come
up with. Than address each area with contiguous blocks so that you can
summarize and keep the routing table as small as possible. The spokes
could be "stubby" sense they have only one way out.

James 


On Mon, 30 Aug 2004 17:54:35 +0200 (CEST), Marcel Lammerse
<lammerse at xs4all.nl> wrote:
> Hi,
> 
> I have a hub-and-spoke network, for which I'd like to use OSPF as a
> routing protocol. The spoke sites will advertise their networks to
> the hub and receive a default route from the hub.
> 
> A common piece of advice in OSPF design literature, is to use different
> area numbers to prevent unnecessary LSA updates from flooding to routers
> that don't need the updates and to avoid the cpu processing overhead.
> 
> The total network has some 50 routers.  There are 3 inter-connected hubs
> and some 15 routers per hub. The way I see it, I can do two things:
> 
> 1.      assign a lot of area numbers to prevent the LSAs from propagating
>        through to routers that don't need them. However, this leads to a
>        relatively complex configuration.
> 
> 2.      accept the, potentially small, bandwidth waste and don't care
>        about the cpu overhead (we're talking 2600XMs here).
> 
> Option 1 just doesn't seem worth it. Could someone provide some advice,
> experience or tips?
> 
> Thanks.
> 
> -Marcel
> 
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