From: Rob Webber (rwebber@xxxxxxxxxxxx)
Date: Wed Jan 24 2001 - 15:39:51 GMT-3
I have been looking at dial quite a bit lately. I'm not sure how/why you
would use dial backup. I understand the basic premise - that it places a BRI
or dialer interface into standby and watches for the main interface to go
down. However even the Cisco doc's indicate that actual dialing only occurs
when there is a packet to be transmitted (via the dialer-list command).
It seems to me (short of using dial watch) the only way you can get it to
dial is by using floating static routes to point traffic to the BRI or
dialer interface. However if you use floating statics, you don't really need
the backup feature at all.
For example, in Cisco's example:
http://www.cisco.com/warp/public/793/access_dial/britobribackup.html
IGRP will not run on the BRI0 because there is no "network 192.168.10.0"
under router igrp 1. So routes will not be dynamically learned once Serial0
goes down. So the only way traffic can route between the two routers in the
example is to have a static default route pointing to the BRI0 with a high
admin distance. Yet if that's the case, why use the backup command at all?
Dial watch seems to be a better solution - it watches specific routes in the
routing table and actually dials as soon as they disappear (at which point
EIGRP or whatever can exchange routes). This also gets away from the "no
static routes" limitation we so often see.
Thoughts?
Thanks - Rob.
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