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SIP to SIP transcode

I have CME 3.4 running a full SIP environment. The 7940 phones register to my 2621XM via SIP on the LAN no problem. My problem starts when I want to use G729 on the SIP trunk over the WAN my VOIP provider. It appears that for some reason CME 3.4 won't transcode between G711 used on the LAN and G729 used on the WAN. According to the sip debug it appears the CME box send a cancel for no apparent reason after it gets a 183 Session in progress from the VOIP. Any help would be appreciated.

Community Member

Re: SIP to SIP transcode

Cisco's IP-to-IP Gateway can do transcoding between G.711ulaw/alaw and various flavors of G.729r8. It uses the Skinny Server when invoking the transcoding services. Transcoding could be invoked for any call whether it originates from CCM or a voice gateway.

Even though transcoding resources is done locally on ipipgw, the transcoding resources have to be registered to a SCCP server

(Either CCM or CME).

Here is a sample config

The only way presently for the IPIPGW to be able to handle transcoding is that it needs to communicate via SCCP to a SCCP server. You can do this on the gateway by configuring the following configuration. This will configure the necessary transcoding and SCCP server.

Here is a sample config:

sccp local

sccp ccm X.X.x.x identifier 1


sccp ccm group 1

associate ccm 1 priority 1

associate profile 1 register MTP

keepalive retries 5

switchover method immediate

switchback method immediate

switchback interval 15


dspfarm profile 1 transcode

codec g711ulaw

codec g711alaw

codec g729ar8

codec g729abr8

codec gsmfr

codec g729r8

maximum sessions 5

associate application SCCP

no shut



load 7960-7940 P00303020214

max-ephones 48

max-dn 48

ip source-address port 2000

sdspfarm units 1

sdspfarm transcode sessions 50

sdspfarm tag 1 MTP

create cnf-files



Community Member

Re: SIP to SIP transcode

Yeah I tried that but my 7940 isn't registering with my CME box via SCCP. Here is my config it might help to clarify what I am attempting to do.

ip dhcp pool ITS




option 150 ip


voice service voip

allow-connections sip to sip


rel1xx disable

registrar server expires max 600 min 60


voice class codec 1

codec preference 1 g711alaw


voice register global

mode cme

source-address port 5060

max-dn 20

max-pool 10

load 7960-7940 P0S3-07-5-00

tftp-path flash:

file text

create profile sync 0003275550914141


voice register dn 1

number 2001

name Computer

preference 1



voice register pool 1

id mac xxxx.xxxx.xxxx

type 7940

number 1 dn 1

max registrations 24

voice-class codec 1

description Computer


interface FastEthernet0/0

ip address dhcp

ip nat inside

duplex auto

speed auto


interface FastEthernet0/1

ip address

duplex auto

speed auto


tftp-server P0S3-07-5-00.bin

tftp-server P0S3-07-5-00.loads

tftp-server P0S3-07-5-00.sb2

tftp-server P003-07-5-00.bin

tftp-server P003-07-5-00.sbn


dial-peer voice 1001 voip

destination-pattern 0..........

codec g729r8

session protocol sipv2

session target ipv4:*.*.*.*

session transport udp

clid restrict



authentication username ****** password *********

no remote-party-id

retry register 2

registrar ipv4:*.*.*.* expires 3600

Any further ideas would be great Thanks

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