Weird "phone-model specific" behavior

[jmcornilla]

Hi Guys,

I'm having some trouble with our setup right now.  I hope you can help me out.

Our client has had a working telephony setup.  Currently, their 2921 voice gateway is having problems with its power supply.  We have provided them with a 2801 service unit and I transferred the configurations.  Now the problem is, the 6921 phones can call outside, but the 7942 phones can't.  The 7942 phones always get a busy tone whenever they try to call an outside number.  I've ruled out connectivity issues because the phones are configured for DHCP, and the IP that I assigned to the service unit is exactly the same as the old router.  I've ruled out CSS configuration as well because no reconfiguration was made to the CallManager.

Jomar

[gmgarrian]

Usually if there is phone specific behavior like this I would suspect the firmware, but if the only change has been the gateway.

Is this an h.323 or MGCP gateway?  Are both phone types using the same route group? If the gateway isn't registered correctly that could be a problem but that would affect both phone types if they're using the same router pattern/list/group.

I think some debugs are in order on the failed calls from the gateway.

[jmcornilla]

Here are the outputs that I took.  I managed to get an isolated environment to test out the two phone models.  Phones and gateway are in the same subnet, they use the same CSS as well.  I see a disconnectcause=172 on the 7942 call.  Any idea on what might cause this?

[gmgarrian]

I found an old email thread on another site mentioning the disconnect cause 172 but it was related to fax relay and 2900 series routers.  Have you opened a TAC case?

[Chad Stachowicz]

Hey guy,

  the 6921 is going out Dial-peer 90 and the 7942 out dial peer 9

Clearly a problem with your circuits... change it to

dial-peer voice 90 pots

preference 1

destination-pattern .

progress_ind setup enable 3

progress_ind alert enable 8

progress_ind progress enable 8

progress_ind disconnect enable 8

port 0/1/1:15

!

That way at least all calls will make it...

Try the 7942 going out this peer, then you can confirm its the circuit on port 0/1/0

Cheers,

Chad

[jmcornilla]

Hey Chad,

I'm a bit hesitant to say that this is a circuit problem because

1. Both ISDN lines are from the same provider
2. When I put the VWIC back to the 2921 router, there are no problems
3. 2 lines, so 60 channels total.  Average call rate of the client is about 10-15 concurrent calls.
4. All 6921 phones are working ok.  All 7942 phones are having problems. Is it possible that a phone model always gets to match a single dial-peer?

[Matt Barber · Accepted solution]

Hi!

Codec difference looks to be the cause of call failure.

3rd gen phones are selecting G.722 as default. Check out the following, you can follow this using your logs as well.

1) When we match these peers, let's see what the disconnect reason is.

------------------ show dial-peer voice ------------------

VoiceEncapPeer9

Successful Calls = 0, Failed Calls = 6, Incomplete Calls = 0

Accepted Calls = 0, Refused Calls = 0,

Last Disconnect Cause is "AC  ",

Last Disconnect Text is "dsp error (172)",

2) So then you can look at the voice call history, also in the sh tech under "show call history voice last 50":

Channel BearerChannel=0/1/0.31 had this error:

DisconnectCause=AC 

DisconnectText=Dsp programming failed

Comparing to a working call on the same platform (search "DisconnectText=normal call clearing (16)") you can see the CODECs are different on the two calls:

Failed call:

CoderTypeRate=g722-64

Working call:

CoderTypeRate=g711ulaw

Quick fix is to add a voice-class codec config, something like this could do the trick:

On the dialpeer, add

voice-class codec 9

Then the voice-class codec config

voice class codec 9

codec pre 1 g711u

codec pre 2 g729r8

You are using PVDM2 DSPs which support G.722 (look at show inventory in the sh tech). Then, look at 'show version' and you'll see there's quite an old IOS on there:

2801 Software (C2801-SPSERVICESK9-M), Version 12.4(15)T9.

Looks like G722 is supported in 12.5 and above (but I didn't look too far, however an IOS upgrade shouldn't take you long to test).

I'd recommend upgrading the IOS and see if that fixes your problem, you'll find the G722 calls go through fine and the calls sound better using the newer codec!

Hope that helps,
Matt