Re: OSPF demand circuits (Lab 8a)

From: Jimmy Dotson (dotsonjl@xxxxxxx)
Date: Fri Jan 19 2001 - 15:52:30 GMT-3


   
You are right. This is what I was getting at in response to an earlier questio
n that had to do with OSPF on dialer interfaces w/on-demand and backup int. In
 this case I would use a backup interface statement on my ethernet interface.
 This puts my BRI in standby state, until the ether fails or drops (I've had pr
oblems forcing this with an admin down - I had to actually pull the ether cable
). This is how I would back up the ethernet in this case. So the only way BRI
 comes up is if the ether is broken.

Jimmy

>>> "R. Benjamin Kessler" <ben@kesslerconsulting.com> 01/19/01 12:27PM >>>
Hi all,

Just a quick question about OSPF demand circuits. I've setup a sub-lab to
test OSPF demand circuits; I've used the doc CD as a reference and have
things working nicely - BRI only dials when a topo change occurs, etc.

The main difference between the CD and the R5/R6 configs for Lab8a is that
in the lab only R6 is configured to dial R5; on the CD both routers dial
both ways.

I modified my lab to emulate that of Lab8 - e.g. two routers connected via
e-net link as primary with BRI as backup and removed the phone number from
R5 so it only accepts calls.

This seems to work also, albeit a bit slower - waiting for the dead interval
and all...my question is as follows:

OSPF topo changes will cause the BRI to dial even if the main interface is
up - if my understanding of OSPF is accurate, I would believe this to be the
desired behavior.

I guess I'm a bit confused by the statement in the lab that "The ISDN
connection should only come up if the ethernet connection is broken;" Given
the above logic, this statement doesn't seem too accurate.

Any insight here?

Thanks,

Ben



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