RE: OSPF Virtual Link across Non-OSPF area?

From: Sam.MicroGate@xxxxxxxxxxxxxx
Date: Fri May 10 2002 - 17:02:47 GMT-3


   
Howard,

If the solution require a Virtual link, can I add both ends of the tunnel to
a new area 2.2.2.2, then create a virtual link across this area?

Sam

-----Original Message-----
From: Howard C. Berkowitz [mailto:hcb@gettcomm.com]
Sent: Friday, May 10, 2002 3:38 PM
To: ccielab@groupstudy.com
Subject: Re: OSPF Virtual Link across Non-OSPF area?

At 2:57 PM -0400 5/10/02, Warner, Thomas S wrote:
>Greetings
>
>I have a quick question regarding OSPF and virtual links. I don't think
>this is possible but here goes anyway - Is it possible to create an OSPF
>virtual link across a non OSPF routing domain (where the routing domain has
>full routing information to get between the two ASBRs)? Normally, if I had
>to connect two areas such as this, I would use another approach such as
>redistribution or migrating the non OSPF routing domain to OSPF, but these
>are not options at the present time.
>
>Area 1 Area 0
> --- R1 --- R2 --- R3 ----
>
>R1 and R3 are running OSPF and R2 is not running OSPF but has static routes
>configured to allow R1 and R3 to communicate. So in this scenario, would I
>be able to connect Area 1 to Area 0 via a virtual link?
>

You certainly can get OSPF connectivity if you set up a GRE tunnel
between OSPF interfaces on R1 and R3, and put both ends of it in area
0.0.0.0. R1 then becomes an ABR and R3 a backbone router; OSPF
doesn't know R2 is there.

In other words, you do need the static routes for R1, 2, and 3 to
communicate, but OSPF won't (and shouldn't) know about them. No
virtual link required.

--
"What Problem are you trying to solve?"
***send Cisco questions to the list, so all can benefit -- not
directly to me***
****************************************************************************
****
Howard C. Berkowitz      hcb@gettcomm.com
Chief Technology Officer, GettLab/Gett Communications
http://www.gettlabs.com
Technical Director, CertificationZone.com http://www.certificationzone.com
"retired" Certified Cisco Systems Instructor (CID) #93005


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