I've come across some strange router behaviour to do with dialer persistant...
One of our customers requires the following solution:-
A router supporting a standard ADSL connection, but with an audio modem backup - so that connectivity can be maintained via an analog dialup if ADSL fails.
The hardware setup is an 837, running the latest available IOS 12.4(13b), with a USR robotics modem sharing the ADSL line (via a splitter) and plugged into the router console port.
The configuration uses dialer persistant on two interfaces and relies on "backup interface" to switch the backup connection on & off.
a) Starting from ADSL up - all fine - can ping outside world.
b) Pull ADSL cable from router - audio modem dials out to ISP & reconnects - all fine.
c) Reconnect ADSL cable to router - audio modem disconnects - ADSL reconnects - all fine.
d) Pull ADSL cable from router 2nd time - audio modem **FAILS** to dial out -
connection stays down permanently.
This is totally repeatable upon router reboot.
Shut/no shut backup interface - no effect
Power cycle audio modem - no effect
no persistant dialer,
--> **fixes** problem temporarily ??? (At least for one DSL failure cycle)
Is this an IOS issue - or am I missing something here ?
The fact that toggling the persistant dialer command on/off fixes the problem - does suggest to me that the issue does not lie with the audio modem.
Thanks in advance,
Please find attached config & debug dialer events for more detail.