From: Jason Guy \(jguy\) (jguy@cisco.com)
Date: Fri Jul 13 2007 - 18:18:47 ART
If you have to connect area 0 to a remote area (ie one that does not
have a direct interface connection to area 0), then typically you use a
virtual link from an existing area 0 ABR to the ABR of the area you need
to connect to area 0.
In the case of stub or nssa being the transit area, you are not allowed
to use a virtual link. So in this case you have to create a tunnel, and
put that tunnel interface into OSPF area 0 on both ends. Now the remote
area has an interface in area 0.
As for the method of bringing up the tunnel, that can be tricky. You
have to make sure the tunnel source and destination addresses area
routable in the transit area. So if you use ip unnumbered, make sure
the address is reachable across the transit area. Also make sure the
source and destination addresses do not become reachable via the tunnel,
or you will see the tunnel interface go up and down repeatedly.
HTH
Jason
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of M
> S
> Sent: Friday, July 13, 2007 4:56 PM
> To: ccielab@groupstudy.com
> Subject: tunnelingOSPF
>
> Hello:
> This is my most dreaded topic.
> Can i get some clarrification on how to use tunnels to replace ospf
area
> virtual-links over stub and nssa areas?
> For virtual links that do not have a common area 0 on both sides one
> should place an ip address on the tunnel
>
> For virtual links that have an area 0 on both sides of the stub area,
I
> think i can use an ip unnumbered interface.
>
> Is this right.
> Thanks
>
>
------------------------------------------------------------------------
>
> See what youre getting intobefore you go there
>
>
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