There is no automatic way to do that..Show commands will inform the modem status but not the telephone line. So you need to plug the analog telephone on that analog telephone line to see the dialtone is there or not. Here are some other ways.
Or you can reverse telnet to modem connected to a telephone line and try to dialout using atdt to a place where you can hear the incoming ring.
If you have relatively idle linux or unix box you could easily write a script to figure out if you're getting a Username: or not and generate an SNMP trap or page you if it doesn't work. Probably less than 25 lines of shell script.
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...