Router A uses ISDN BRI to connect to Router B. Router B also has a T1 card that connects to our hub. Router A maintains a 24/7 connection. Up until last Friday I had no problems. Suddenly, Router B will receive the call from Router A and then disconnect it. Running 'debug isdn all' shows no error messages on Router B. Running 'debug isdn q931' on Router A shows no error messages. I have 5 such setups and two failed at the same time (thunderstorms?). Replaced the ISDN card, no effect. Phone company has verified that the ISDN circuits are working correctly. I REALLY need help on this.