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iLBC and MGCP/2811/IOS15.1/PVDM2-48

We have CUCM 9.1(1)/Unity Connection 9.1(1) integrated with iLBC codec via SIP trunk from CUCM. Works fine internally.


User's 7965 rings but PSTN hears fast busy upon CFB/CFNA to voicemail.  CCM traces show transcoder being invoked (we don't have one setup, I was wanting MGCP gateway to Unity Connection to be iLBC no xcoder by design)


Doesn’t appear that my IOS15-1/2811/MGCP/PVDM2-48 can do iLBC….or do I have something wrong with my mgcp config? Everything else works great but this SIP/iLBC setup.


voice-card 0

dsp service dspfarm

codec complexity flex


controller t1 0/0/0

pri-group timeslots 1-4 service mgcp


interface Serial0/0/0:23

isdn bind-l3 ccm-manager


mgcp codec ilbc

ccm-manager mgcp codec-all

no mgcp



debug mgcp packet at gateway I see G711

*May 24 21:50:34.933: MGCP Packet sent to>

200 526 OK

I: 3


c=IN IP4  <<<Gateway IP

m=audio 16948 RTP/AVP 0 100  <<<<shows g711, and no iLBC capability

a=rtpmap:100 X-NSE/8000

a=fmtp:100 192-194



Everyone's tags (1)
Cisco Employee

Hi Jason,You might want to

Hi Jason,

You might want to try one of the fixed versions of the following bug

iLBC codec on MGCP GW not supported with IOS 15.2(1)T

MGCP GW configuration:
ccm-manager mgcp codec-all
mgcp codec ilbc mode 20 packetization-period 60

CUCM configuration:
region with iLBC settings created

it works with earlier IOS (15.1(3)T2)




I am running c2800nm

I am running c2800nm-advipservicesk9-mz.151-4.M7.bin

The bug ID indicates it is only for 15.2T.  But it would imply that this should work.

However I can change from 15.1.4M7 to 15.1.4M8 or down to a lower version to see if that fixes it.




I changed to 15.1.4M8 (March

I changed to 15.1.4M8 (March 2014) the most recent IOS.

I took CUC out of the equation and am just trying to get MGCP/Gateway to 7965/SCCP/8.5.4S to be iLBC and that is failing.

clear log

debug mgcp packet  <<<< make test call and view log file

2811#show ver | inc System image
System image file is "flash:c2800nm-advipservicesk9-mz.151-4.M8.bin"
2811#show log | inc L:
L: p:20, a:G.729b, s:off, t:b8
L: p:20, a:G.729b, s:off, t:b8


Hi Jason,

Hi Jason,

Did you find a solution? I'm getting same issue. CUCM is only negotiating G.729 or G.711 not iLBC

These two command are already applied on MGCP GW:

ccm-manager mgcp codec-all
mgcp codec ilbc

Running version Version 15.1(4)M10 and CUCM 9.1.2.

Thanks in advance

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