How many routers in OSPF area?

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Quick question for you OSPF gurus::
   I know that Cisco states that 50-100 routers is the max for an OSPF area.
Does anyone have experience with a single area comprised of about 150
routers? I'm a little nervous about pushing the limit.


Re: How many routers in OSPF area?
The routers in the area haven't got enough processing power for more than
150 routers in one area. It's better to create small area's. I don't think
it's a very good idea to put more routers in one area, than 50.

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Re: How many routers in OSPF area?
cisco_guru wrote:
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OUCH! 150+ routers?!  That pretty much defeats OSPF's most significant
feature: the ability to parcelize large routing domains in order to
streamline the convergence /SPF process!

Essentially with a pool this big your giving up the ability to
effectively summarize routes...ergo a huge routing table within every
device in the area. Dont forget: OSPF is pretty CPU and memory intensive
process.  I have no idea what type of hardware your running, but if you
have any old gear deployed -many do- (i.e Cat5500 with RSMs or 4500s
etc.) you are just begging for trouble!  (BTW.. Is it a single flat area
0? -- that would really hurt!).

The next issue is physical/Geographical topology.  With 150+ devices, I
cant imagine they're all in one building (unless you're in the Sears
Tower!) ... That says that there are likely are going to be WAN type
links between some of these devices, correct?  So now your configuration
complexity just went up...any links Frame-Relay or ATM? If so, recall
how OSPF behaves over non-broadcast networks!  It could be you're a
lucky guy and everything is connected over a Gig-E MAN... but still any
single link outage will be felt across the entire network.

I strongly suggest you re-think your routing strategy or consider a
different routing algorithm

Good Luck!


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