[cisco-voip] NM-HDA FXO ports ground line during reboot

[Ryan Ratliff]

You should definitely open a TAC SR to find out if this is expected behavior
or not. 


-Ryan 
-----Original Message-----
From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Dan Lanciani
Sent: Wednesday, November 26, 2008 4:03 AM
To: cisco-voip at puck.nether.net
Subject: [cisco-voip] NM-HDA FXO ports ground line during reboot

I noticed that when I reload the router phone lines connected to FXO ports
on NM-HDA cards go busy until the router comes back up.  Closer
investigation revealed that one side of the line is being grounded as if the
port were trying to busyout a ground-start trunk.  (These are regular
loop-start lines and the FXO ports work fine with them when the router is
up.)  I tried two different NM-HDA cards in two different routers (3640,
3660) with 12.4 and 12.4T IOS releases; all behave the same.

This effect is disturbing because it means my lines would be out of service
if the router ever fails to come back up.  I played with various
configuration options but I couldn't find any way to disable this
feature(?).  Getting a little frustrated I physically modified the NM-HDA
FXO card by unsoldering and lifting the pins of the solid state relays that
are used to apply ground to the lines.  This "solves" the problem but of
course the cards will no longer support ground-start lines and my SMD
soldering capabilities aren't that great, so I'd prefer a software solution.
Also, should the code get clever and (assuming this is indeed a feature) try
to busyout the line correctly for a loop-start I'll be back where I started.

Has anyone encountered this on NM-HDA cards or any other FXO interface?

				Dan Lanciani
				ddl at danlan.*com
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