Cisco 7931 IP phone Codec ILBC not working

[network_user]

Hello,

I have a cisco 7931 IP phone connected/registered to a CME. CME has a SIP trunk to a third party voice provider and the negotiated codec on the SIP trunk is configured to be ILBC. The SIP trunk seems to be working fine with the ilbc codec, however when a call is placed to the Cisco 7931 IP phone, it rings, but when someone picks it up it gets disconnected with disconnect cause: 172. Below is the debug output of debug ccsip calls. Is this because the phone is not configured to use ilbc codec? how can I resolve this issue? I have removed the real IP addresses/phone numbers for security.

I cannot configure the "ephone" with the codec ilbc on the CME. It gives only option for G711/G729.

The Call Setup Information is:

Call Control Block (CCB) : 0x4887DB08

State of The Call        : STATE_DEAD

TCP Sockets Used         : NO

Calling Number           :<PSTN PHONE>

Called Number            : <7931-PHONE>

Source IP Address (Sig  ): <cme_ip_address>

Destn SIP Req Addr:Port  : <SIP-SERVER>:5060

Destn SIP Resp Addr:Port : <SIP-SERVER>:5060

Destination Name         : <SIP-SERVER>

*Mar 31 09:12:46.855: //219456/8BC9E1509A28/SIP/Call/sipSPIMediaCallInfo:

Number of Media Streams: 1

Media Stream             : 1

Negotiated Codec         : ilbc

Negotiated Codec Bytes   : 50

Nego. Codec payload      : 97 (tx), 97 (rx)

Negotiated Dtmf-relay    : 0

Dtmf-relay Payload       : 0 (tx), 0 (rx)

Source IP Address (Media): <cme_ip_address>

Source IP Port    (Media): 17256

Destn  IP Address (Media): <SIP-SERVER>

Destn  IP Port    (Media): 25832

Orig Destn IP Address:Port (Media): 0.0.0.0:0

*Mar 31 09:12:46.855: //219456/8BC9E1509A28/SIP/Call/sipSPICallInfo:

Disconnect Cause (CC)    : 172

Disconnect Cause (SIP)   : 200

Thanks!

[Nadeem Ahmed]

Hello,

what is your IOS version running the VGW? I am running IOS version (C2900-UNIVERSALK9-M), Version 15.6(2)T and able to configure iLBC under the ephone

(config)#ephone 7
(config-ephone)#cod
(config-ephone)#codec ?
  G722-64K  Use G.722 64k bps voice codec
  g711ulaw  Use G.711 u Law 64000 bps voice codec (default)
  g729r8    Use G.729 8000 bps voice codec to save network bandwidth
  ilbc      Use iLBC 20ms voice codec

Br,

Nadeem

[network_user]

Hello Nadeem,

I am running Cisco IOS Software, 2800 Software (C2800NM-ADVIPSERVICESK9-M), Version 12.4(15)T 7, RELEASE SOFTWARE (fc3) on this router. 

Do you think that could be the issue?

Thanks!

[Nadeem Ahmed]

it could be one of the reason but you can validate the same by checking the release of this IOS version.