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Webcast-Catalyst9k
New Member

OSPF Multiple areas

Hi

i want to ask about the benefits of having Multiple areas in OSPF network..?

i see that the only benefit is optimizing routing updates..and making summerization on ABRs.., but if the networks are not distributed contigiosly across the network.., and i can not make any kind of summerization.., why should i have Multiple areas..??

can anyone help ??

M.gamal

5 REPLIES
Silver

Re: OSPF Multiple areas

You can have multiple areas to contain your routing updates within your area, thereby the ospf database would be smaller resulting in faster convergence. If there is a link instability in your area that will not disturb other areas, if you have multiple areas. Summarization is also a very big benefit of this hierarchial structure, and everyone should consider making their networks contiguous.

New Member

Re: OSPF Multiple areas

well, yes you are right..but what i see in my network that all routers are having similar database, and contains all routes from all areas..

i even made a simple test..i added a loopback interface with an IP on a router in area-1, and watched what happends if i shut it and no shut it again..on a router in area-2.

and what i saw is that this IP address appears and dissapears as i shut and no shut the loopback.., plus the SPF calculations increases..

so i am having no benefits for having multiple areas..

am i right..or am i doing something wrong..??

Regards

M.Gamal

New Member

Re: OSPF Multiple areas

Hi,

I guess you can't see any impact for loopback interfaces as they are virtual interfaces and in most OSPF network it is defined as passive interface. I think you would have tried with any point-to-point/ethernet interfaces as ospf is based on LINK STATE algorithm (the stress is at link state).

Moreover ospf is multicasting based, which allows you any advertisement is limited to that particular group i.e. your area alone.

Whether you need backbone or not can be decided according to the route entries in your routing table and merits said at other reply .

Hope this helps

Dinesh

New Member

Re: OSPF Multiple areas

ok..i tried it wz ethernet link..and as i said , when i shut down the ethernet of a router located in area-1, i can see this on a router located in area-2..and the SPF calculations increments..

i am having a backbone area separating between them..

what i want to say is in my case i am not having any benefit from multiple areas ospf....if i am worng , tell me

M.Gamal

New Member

Re: OSPF Multiple areas

Hi,

Define your area 2 under different process id , this will not reflect at area 1. However its a overhead to the router, not recommended for the same autonomous system.

For an autonomous system a backbone and a single area is suffice, you don't need multiple areas.

Dinesh

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