From: Shibu Nair (shinair@cisco.com)
Date: Mon Jun 28 2004 - 13:48:38 GMT-3
Here are my inputs... OR my rules.
Rule 1:
Tunnel source and destination should be reachable.
So i would put the ip address Ry fas 0/1 as tunnel destination on
Rx. And Rx E0 ip add as the tunnel source on Rx. Vice versa on Ry.
Since this ethernet media is directly connected i do not see any
readability pblms.
Rule 2:
Both Tunnel ip addresses should be part of area 0.
option 1: Interface Tunnel with its own ip address and put this ip as
part of its area 0.
option 2: Interface tunnel does not have the direct ip addresses instead
using loopack ip address (unnumbered). In this case put the corresponding
loopback address as part of its (Rx / Ry) area 0.
Rule3:
Give a high cost/metrics for the tunnel path to avoid recursive loops.
or make sure the static routes does this.
Ensure that tunnel source or destinations ip addresses are not learned
through the tunnel itself.
If you have inconsistency on the above rules your tunnel might flaps.
Try these in the lab.
Regards
Shibu
At 11:12 AM 6/28/2004 -0400, ccie2be wrote:
>Hi guys,
>
>What's the advantage or disadvantage of using a virtual link to connect a
>discontinuous ospf backbone area vs using a tunnel to do the same thing?
>
>Besides the authentications available with a virtual link, are there any other
>differences?
>
>Also, let's assume I wanted to use a tunnel in the following scenario:
>
>Area0 --- s0 Rx E0 --- Area xy --- fa0/1 Ry s1 --- Area0
>
>
>Rx and Ry share a common ethernet subnet and each also has a loopback0
>interface.
>
>What should the endpoints of the tunnel be?
>
>Should any pair of endpoints work as long as they're consistent on both Rx and
>Ry? Why yes or no?
>
>Does it matter what area the physical or loopback interfaces endpoints of the
>tunnel are assigned to?
>
>I know that when the loopback interfaces are put in area 0 and the ip addr of
>the tunnel itself is assigned to area 0, this config works. But, I tried
>other which didn't work but I don't understand why.
>
>Could someone explain why that is?
>
>TIA, Tim
>
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