While detailed troubleshooting is required, yet from my past practical experience of similar problem of ISDN call getting cleared after some time , i can say that it may be an IOS problem. It is expected that with newer versions of IOS software basic things like ISDN would work flawlessly , but that is not so with some of newer releases of Cisco IOS. That means you have to check all the features you intend to use and cann't take them granted for in newer releases.
I suggest that you may try, as i did, to use some earlier version of s/w on the same platform.
- Manish Garg
New Delhi.
India
mkgarg2001@rediffmail.com
