lost audio after 5 minutes

Unanswered Question
Feb 26th, 2010

Network topology:

[CUCM]    <=> [2811 GW Pri T1]   <=>  [PSTN  / Allstream]            (Site 1)

                <=> [1861 GW FXO]      <=>  [PSTN / Allstream]            (Site 2)

                <=> [1861 GW FXO]      <=>  [PSTN / Telus]                  (Site 3)


We setup new site (Site 3), Calling from [PSTN] to CUCM IP Phone.

IF call come from site 3 1861 FXO GW  only have audio 5 minutes.

All call if short then 5 minutes working fine.

After 5 minutes no audio in both directions,Both side IP phones still stay connected, phone time counter is incrementing.

At router debug vmp sign (see nothing when the audio lost) .

sh voice call sum (see the line still up).

I already open a TAC, no result yet.

Any suggestion ?

I have this problem too.
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gogasca Tue, 03/02/2010 - 07:29

Whcih protocol you are using H.323, SIP or MGCP?

Any firewall, security device or NAT in the middle of GW and CUCM?

steve7388 Wed, 03/03/2010 - 10:10

It is H323 GW. And there is GW between GW and CUCM

So far we find audio drop reason is:

The GW did not receive the H323 keepalives message.

After the 4 keepalive is missed timeout (about 5 minutes). Call dropped.

I sniff the CUCM port found that the CUCM send keepalive just after 5

minutes. This means when CUCM send the keepalive message the GW already

dropped the line.

So the phone show line is UP and the audio lost.

emorivera2526 Wed, 03/03/2010 - 19:48


I had a client with a similiar issue.  After approximately 5 minutes the calls would drop going across the WAN.  Local calls were fine, only LD and/or International calls would drop when traversing the WAN.  Pretty much the same set up as you.

What ended up being the issue for me was a missing command:

H323-Gateway voip interface

The previous engineers who installed it did not add this command, among others.  The funny thing is this environment had been up and running for a couple years with no issues until one day it started failing.

Anyways - verify your H323 configuration on BOTH gateways (binding and interface commands)

One other thing to check is your firewall configurations.  If you're running an ASA or PIX with an older image, there is a bug with the H323 Inspect which would cause timeouts.

Hope this helps



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