CUCM 4.2 Random one way audio/dropped calls

Unanswered Question
Nov 25th, 2009

I have a client with a CUCM 4.2 using two separate 2811 as MGCP gateways, each with a PRI T1 for inbound/outbound calls.

We're having a problem with seemingly random inbound calls that will have one way audio.  The receptionist will answer an inbound call and she will be able to hear the caller but the caller will not be able to hear her.  The caller will hang up and call back and this time everything works fine.  The inbound calls this happens to have been long distance (from a different area code) but other than that they're pretty ramdom.  Over eight different area codes.

Also, this may be a separate isssue, but randomly an outbound call will drop once the called party answers.  Calling back will be successful.

This site is pretty static and no changes have been made to the gateways for months (if not years) prior to this problem starting.

We have our telco looking into things on their end but I wanted to see if anyone here has any thoughts as to what I can check.

Thanks in advance!

G

I have this problem too.
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vivkalra Sat, 11/28/2009 - 18:45

One way audio intermittent smells like could be an issue with the DSP,s on the router.

If we are using the complex codec say(G729) in our voice system and call coming through the

gateway is g711 call so would require the trancoders to communicate.

So in case DSP are not allocated properly or DSP channel does not respond properly can give one way audio

A shot you can try is upgrading the call manager and IOS of the gateway to the latest release

Else you need the packet captures and traces to go deep in cause.

gmgarrian Tue, 12/01/2009 - 08:40

This is a single site with inbound calls from a T1 PRI and G711 is the only codec in play.  That being said, the DSPs on the router are not showing any errors.  Is there a better way to check them?

vivkalra Tue, 12/01/2009 - 11:17

You can check the state of dsp's by command

# Show voice dsp voice

gmgarrian Tue, 12/01/2009 - 11:25

I've attached a bunch of outputs.  It seems like one of the dsp slots isnt' showing up, but I'm not sure if that's normal or not.

In the show diag there are two PVDM slots with a dsp daughter card (0 and 1) but in the test voice driver app is doesn't see anything in slot 1.

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