[c-nsp] OSPF area design question

[Marcel Lammerse]

Ok, if you have that area 1 with 15 routers. Would it be a good idea to 
keep them all in one area, or would it make sense to assign 15 
different area numbers and make each of them a separate area (NSSA in 
this case). Because, I figured, an update from one of the router will 
be flooded throughout the entire area which is totally unnecessary.

I like to know whether the extra configuration and administrative 
overhead is worth saving on unnecessary update floods and cpu cycles 
processing them.

On Aug 30, 2004, at 9:47 PM, James Hampton wrote:

> 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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>
>
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