Spoofing is what you want your backup line to be doing while your leased line is down - until traffic of interest is presented to the DDR interface. That is, unless you just want the ISDN up 24X7 when the leased line is down.
You would need to list more of your config to find the problem. Remeber that there are several ways to go about it. The easiest way is to define a dialer-group on your DDR interface and have a matching access-list that defines your traffic of interest.
Don't forget your static routes (of higher cost than your routing protocol)!
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...