Modems lose dial tone on AIX, require power cycle to restore

Posted on 2007-03-19
Last Modified: 2013-12-27
I've got an application running on AIX v4.3.3.0 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?
Question by:jjmartin
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LVL 57

Accepted Solution

giltjr earned 175 total points
ID: 18759835
Connect a phone to the phone port on the back of the modem, pick it up and see if you hear dial tone.

It could be that the modems are starting to show their age and something inside is going bad.

Author Comment

ID: 18767000
It could be the modems... and I'm gettting some new ones, but it just seems odd that all of them would start having problems at virutally the same time.
LVL 57

Assisted Solution

giltjr earned 175 total points
ID: 18768259
Are both the power cords and modem cords going through surge protectors?  How old are they?

Surge protectors wear out.  How long they last is dependent on how many power surges/lighting strikes they have had to suppress.

If they old, or you don't have any, have you had any recent power issues or lighting storms in your area?

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Author Comment

ID: 18775074
The hardware is in an extremely secure environment.  The likelyhood of any type of power event causing a problem is very very low.  There is another server in the same rack with that is setup virtually identical to the one with problems, and is under pretty much the same load, if not greater.  It's not having any problems, and it went into service at the same time.  it's just the modems connected to this one server.
LVL 62

Assisted Solution

gheist earned 75 total points
ID: 18784564
Modem hang is modem internal problem. Easiest to solve with firmware update.
If crashes persist after update - you have to trace down what commands caused them.

Author Comment

ID: 18906543
This is what finally happened.

There are three modems connected to the server.

1 directly connected to an on-board serial port. (modem 1)
2 connected to an 8 port serial port expansion card installed on the server. (modem 2 and 3).

If I enabled modem 1, it would die after a few hours (no dialtone).  Then modem 2 and 3 would follow several hours later (but not at the same time).

If I left modem 1 disabled, then modem 2 and 3 would work just fine.

Cycling the app that uses the modems, and rebooting the server wouldn't recover the modems.  The modems would have to be physically powered off and on.

I've replaced all the modems, and now all 3 are working fine, still connected to the same serial ports.

LVL 57

Expert Comment

ID: 18906683
I agree, that is weird.

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