OSPF Area 0 IP addressing

Answered Question
Feb 6th, 2009
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Hi all,


I'm getting ready to split my single area OSPF network into a multi-area deployment. Right now all the links between my core devices are either /30 or /29 in the 10.5.0.0/24 address space. My concern is that after splitting the areas there will still be some of those address spaces outside of Area 0. Should I change the address space I use in Area 0, and if so, what would you recommend?


Thanks

Correct Answer by paolo bevilacqua about 8 years 3 months ago

Yes. A reasonable amount of prefixes to start thinking area segmentation is perhaps around 1000, with frequent flapping and intensive SPF recalc.


Instead you have a small network, try to keep it the simple as possible.

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paolo bevilacqua Fri, 02/06/2009 - 12:40
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Sorry, how may prefixes you have, any issue running area 0 only ?

The idea is exactly to avoid the issues you're going toward, and you didn't even began using it.

branfarm1 Fri, 02/06/2009 - 12:59
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Well, we don't have any issues running area 0 only right now. Just that any reconvergence anywhere in the WAN causes the whole thing to reconverge. I know that's the point, but I wanted to do multi-area OSPF so that our future expansion can isolate individual sites from problems in the WAN.


Right now we have 3 sites, using LAN addresses 10.20.0.0 /16, 10.100.0.0 /16, and 10.70.0.0 /16, respectively. All of the WAN interfaces at all sites are subnets of 10.50.0.0/24.


I guess my overall goal was to add multiarea ospf so each site only had to advertise one summary route. Am I wasting my time?

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paolo bevilacqua Fri, 02/06/2009 - 13:34
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Yes. A reasonable amount of prefixes to start thinking area segmentation is perhaps around 1000, with frequent flapping and intensive SPF recalc.


Instead you have a small network, try to keep it the simple as possible.

branfarm1 Fri, 02/06/2009 - 13:53
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Thanks for the help. I'll be back when I hit 1000 :)

paolo bevilacqua Fri, 02/06/2009 - 13:55
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In the meanwhile you can get few cheap routers for a lab and experiment what if ...


Thanks for the nice rating and good luck!

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