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Re: OSPF area [7:79220] posted 11/14/2003
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Not sure if the question is "why would I do that" or "can I do that". I
would say the first one needs to be answered first, probably by the person
who actually asked this question. :)

Fred Reimer wrote:
> Cisco recommends keeping an area to less than about 50 routers, 
> but that recommendation may be quite old.

Yes, very old, so I would say "Cisco used to recommend" this.

This is an age old question, similar to "how fast is BGP convergence?" There
is no way to answer without knowing the specifics like how many links you
have and how stable they are, how much memory the routers have and how fast
their CPUs are and what else they need to do besides OSPF, etc. In fact I am
not sure if it is always possible to answer knowing all the specifics. IMHO
the only sure thing is to monitor CPU and memory usage and investigate if
they hit a high water mark, but that might be a post-mortem investigation,
if you are not careful. :)

So accordingly, I would say start monitoring the routers (if you haven't
done so in the past), and if everything looks fine, then start gradually
moving the routers from other areas into area 0. If you start to see
problems like continous high CPU utilization or frequent spikes, then stop
and investigate. Of course, knowing the network, you will be able to make
educated guesses as to which regularly flapping links or slow routers to
exclude, which router's memory to upgrade first, etc.



> If you are running later hardware, then you should be able to
> get away with 60 routers. If you have a bunch of old
> routers, I'd stick with multiple areas...
> On 14 Nov 2003 at 15:11, Ida Leung wrote:
> > I have a network with about 60 routers running OSPF in 3
> different
> > areas.  Thinking to bring them back to area0.  Want to listen
> your guys
> > opinion.
> > 
> > ..ida
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> Fred Reimer - CCNA
> Eclipsys Corporation, 200 Ashford Center North, Atlanta, GA
> 30338
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