From: Chuck Larrieu (chuck@xxxxxxxxxxxxx)
Date: Wed Jan 03 2001 - 05:18:10 GMT-3
For lack of a better term.
Got to fool around with a few more routers than normal. So I set up a
contrived OSPF topology for the sole purpose of seeing if virtual links can
be dynamic.
The short answer - yes they can
The long answer - in a situation where the transit area terminates to the
same ABR via more than one path, the virtual link can be dynamic, in that if
one path to the ABR goes down then the link reestablishes itself via the
other path.
Router---area_1-----router-------area1
| | \
area_3 area_1 \
| --------router_ABR----area_0
pretty neet, albeit a bit impractical. But it is a question I've not been
able to test empirically until now. The area 0 ABR router will apparently
reestablish the virtual link within just a couple of seconds ( in this lab,
anyway ) The cost of the virtual link was adjusted to reflect the cost of
the underlying OSPF path. By issuing shut and no shut commands on an
appropriate interface I was able to look at the results. The original
virtual link path would not reassert itself when the blocked interface came
up. I would have to issue a shut on the interface of the replacement path.
So I conclude that a virtual link is about as permanent as it gets. The path
remains static, until such time as it disappears, at which point the link
will reestablish itself using the alternative path.
Whelp, back to the books.
Chuck
----------------------
I am Locutus, a CCIE Lab Proctor. Xx_Brain_dumps_xX are futile. Your life as
it has been is over ( if you hope to pass ) From this time forward, you will
study US!
( apologies to the folks at Star Trek TNG )
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