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OSPF, 2 routers, 2 areas, one link

Hello! Please help: we have 2 routers, 2 areas (0 and 10) and only one 10G link between them. Right now this link belong to area 0, so area 10 is discontigous.

What is the right solution for this situation?

27 REPLIES 27
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Hall of Fame Guru

Re: OSPF, 2 routers, 2 areas, one link

m.sobolev wrote:

Hello! Please help: we have 2 routers, 2 areas (0 and 10) and only one 10G link between them. Right now this link belong to area 0, so area 10 is discontigous.

What is the right solution for this situation?

Sorry, it's not clear what you mean, could you draw a topology diagram to show exactly what you mean.

Jon

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Beginner

Re: OSPF, 2 routers, 2 areas, one link

Drawing1.jpg

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Hall of Fame Guru

Re: OSPF, 2 routers, 2 areas, one link

m.sobolev wrote:

Drawing1.jpg

Thanks for the diagram, makes it a lot clearer.

As to the solution, a bit difficult to say without knowing why it is like this in the first place.

why is the link in area 0 ?

why are the vlan 10/20 interfaces in area 10 ?

do you need 2 areas or could you just place vlan 10/20 in area 0 ?

How much of your network does the diagram represent ?

Jon

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Beginner

Re: OSPF, 2 routers, 2 areas, one link

Drawing1.jpg

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Beginner

Re: OSPF, 2 routers, 2 areas, one link

http://img12.imageshack.us/img12/3024/drawing1n.jpg

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Re: OSPF, 2 routers, 2 areas, one link

Hi,

I will suggests to make separate area for area 20 in Router B and it will work in ospf world without any problem.

hope this helps

Regards

Ganesh.H

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Beginner

Re: OSPF, 2 routers, 2 areas, one link

To make things little bit more interresting:

http://img12.imageshack.us/img12/9008/drawing2q.jpg

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Re: OSPF, 2 routers, 2 areas, one link

What is the subnet between Router A and Router B fo Area 0.

Regards

Ganesh.H

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Beginner

Re: OSPF, 2 routers, 2 areas, one link

Link between switches it L2 trunk, and OSPF runs on SVI, subnet /30, for example 10.32.0.0/30

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Re: OSPF, 2 routers, 2 areas, one link

It will work but you need to configure ip unnumbered for wan interfaces.

hope this will work !!

Regards

Ganesh.H

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Hall of Fame Guru

Re: OSPF, 2 routers, 2 areas, one link

m.sobolev wrote:

To make things little bit more interresting:

http://img12.imageshack.us/img12/9008/drawing2q.jpg

Actually this is valid ie. you don't have a problem with the above topology because area 10 is not discontiguous, unlike your earlier diagram.

Jon

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Beginner

Re: OSPF, 2 routers, 2 areas, one link

I dont get it

I think switch A and switch B each run its own ospf process and both of them serves area 0 and area 10, but between them there is only area 0, so area 10 seems to be discontigous?

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Hall of Fame Guru

Re: OSPF, 2 routers, 2 areas, one link

m.sobolev wrote:

I dont get it

I think switch A and switch B each run its own ospf process and both of them serves area 0 and area 10, but between them there is only area 0, so area 10 seems to be discontigous?

Don't worry, it's me not getting it For some reason i though the switches were routers and you have a L2 switch connecting the vlan 10 interfaces. Apologies for being a bit dense !!

Could you not run the link between the 2 switches as a L2 trunk ?

Jon

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Beginner

Re: OSPF, 2 routers, 2 areas, one link

L2 trunk is key design feature, you can imagine switches are datacenters connected by dark fiber and we need shared L2 domain for server farms

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