Dear all expert,
Kindly help me to answer the ISDN question.
I have a router which using the the IOS -- flash:c3825-advipservicesk9-mz.124-9.T1.bin.
I had configure the #backup interface dialer88 on the serial0/0,
dialer88 is a dialer profile to trigger ISDN.
At the same time, i configure the floating static too.
#ip route 0.0.0.0 0.0.0.0 dialer88.
As i start to test the ISDN, i shut the serial0/0.
The isdn was not triggering or kick in, and i double check the dialer88,
it directly go through disable mode and shut the interface automatic.
Once i remove the #backup interface dialer88 on the serial0/0,
the dialer88 is up and triggering soon.
My question now is .....
Is it IOS issues/bug, or new feature for the IOS to prevent administrative use double backup method -- such as #backup interface with floating static together ??
As I attempted to explain in my first post: the backup interface will activate only in the case of a "failure" of the primary interface. And doing shutdown on the serial is not interpreted as a "failure" by IOS. (the assumption is that if you shut it down you did it on purpose and that is not a failure) To get the backup interface to work you must do something that produces a "failure" of the primary (disconnect the primary, change the encapsulation of the primary, disable keepalive on the remote end of the primary - are all things that I have successfully used to test backup interface).
This behavior is common over all releases of IOS. So it is not anything about this particular router or about the version of code that you are running.