I've got an application running on AIX v220.127.116.11 that uses some external US Robotics 56k modems for dial out. It was relatively problem free for about 4 years, and in the past couple weeiks, the external modems have started losing dial tone. I've had the phone lines checked, and they are working. There are four external modems, and they all eventually die (one at a time, sometimes within hours of each other, sometimes days apart). The only way to recover the modems is to turn them off and back on. Resetting them programatically doesn't work, rebooting the server doesn't fix anything.
It seems unusual that all four modems would have problems at the same time, but I can't think of what would be causing this from the server end.
Any idea? Any diagnostics that can be run from the server?