OSPF Area Design

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May 22nd, 2007
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Hello to all,

well, i know this one was discussed more then once in this forum but i still have difficulties to comprehend the OSPF Area design. I've attached a design (WAN1)which i think it is the best practice but i?m not sure.

The links between the backbone routers to all R (except R3 and R6) are in Area 0. If i place only the links between the (B)ackbone Routers in area 0 and the other links in different areas i?ve still an area which doesnt connect to area 0 (between R1 and R2 and R4 and R5) See attachement (WAN2).

I would appreciate if you can give me any hint or advice on this.

Thank you.

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vmiller Tue, 05/22/2007 - 07:45
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I think you are making things too complicated.

Area 0 is for transit between different areas of the ospf network. IMHO drop the inter area stuff that does not connect to 0, plan out your addressing and summarization real well. then just let the backbone do all the heavy lifting.

Wilson Samuel Tue, 05/22/2007 - 08:13
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H Monster,

We would be in much better position to guide you, if you would give a bit more details on the following aspect:-

1. Is it real scenario or lab?

2. If its real life scenario, please specify if the 'Transit Area is a populated Area or its just a Pointt-to-Point link?

3. In theory the qualification of Area = All Areas MUST be connected (directly or indirectly) connected to the Area 0

I guess you may have got a clue to go ahead from here.

I hope that helps.

Kindly rate if it helps

Kind Regards,

Wilson Samuel

syntaxmonster Tue, 05/22/2007 - 22:57
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thank you for your quick replies.

So let me be more precise:

this scenario is what i would like to achieve and it will be a real life scenario.

I?ve planed the address space so that i can summarize:






The link between B1 and B2 are 100Mbit/fdx Ethernet (in near future 1Gb)

The other links from R(n) to B1 and B2 are 10Mbit/fdx Point-to-Point.

My goal is of course to summarize these networks.

So from the area point of view, what do you think is the best set up?

Thank you once again.


ggochev Wed, 05/23/2007 - 01:12
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I think 2 design are good,but importance is when you must use WAN1 example and WAN2 example.

Good Luck!!

Wilson Samuel Wed, 05/23/2007 - 06:23
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Hi Monster,

Let me re-phrase one of my points:-

1. What would be the link type between R1<==>R2 and R5<==>R4?

If its just a point to point link with no hosts in between then the best way to go ahead is NOT to define any OSPF Areas at all rather use the redistrubt static command to make other routers aware of this link.

I hope I'm clear about my point, please get back to us with your point.


Please rate if it does help,

Kind Regards,

Wilson Samuel

syntaxmonster Wed, 05/23/2007 - 22:10
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Hello Samuel,

thank you for your comment. Yes, you?re right, the links R1<->R2 and R4<->R5 are point-to-point (10Mbit/FDX Ethernet) and there are no hosts between. In fact this links causes me headache: you mean i should configure static routes between this links.

Does it meake sense if i put those links in area 0? The routing should then be fine between those location cause of the costs.

Thank you once again for your time.

Kind regards,


sdoremus33 Wed, 05/23/2007 - 16:32
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Generally you should place the summarized routes @the ABR in the network.As you know the purpose of stub areas allow Link state and router updates to the transit areas In the areas that are stub, the purpose of the ABR's is that you (point to)a DG that sends summary updates(floods)to the other areas in this diagram.When you follow this design you conserve resources by only updating link state and router information.HTH Later

syntaxmonster Wed, 05/23/2007 - 22:13
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Hi sdoremus33,

yes you?re right this is what i thought about also. Please see the attached image for a overview.

Kind regards,




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