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SIP Registered Fax Calls Using Only PCMU.

I have a client using a SIP Fax machine (Ricoh MFD) registered with CUCM 10.5 and the machine/extension is able to receive external calls/faxes fine. It is when he tries to make and outbound call that they fail.

If the the MFD is powered off and the extension/account registered with on a 3CX softphone, the outbound calls work fine without any issues.

I collected the debugs on GW and in the SDP noticed that for the working call, both PCMA and PCMU were being negotiated, while for the non-working call, only PCMU was being negotiated:-

---

v=0

o=CiscoSystemsCCM-SIP 179406599 1 IN IP4 10.252.128.130

s=SIP Call

c=IN IP4 10.107.228.147

b=TIAS:64000

b=AS:64

t=0 0

m=audio 40016 RTP/AVP 0 8 3 101

a=ptime:20

a=rtpmap:0 PCMU/8000

a=rtpmap:8 PCMA/8000 >>>>>>>>>> working in this case

a=rtpmap:3 GSM/8000

a=rtpmap:101 telephone-event/8000

a=fmtp:101 0-15

 

 

v=0

o=CiscoSystemsCCM-SIP 179319315 1 IN IP4 10.252.128.130

s=SIP Call

c=IN IP4 10.252.255.162

b=TIAS:64000

b=AS:64

t=0 0

m=audio 30002 RTP/AVP 0 101

a=rtpmap:0 PCMU/8000 >>>>>>>>>> not working in this case

a=rtpmap:101 telephone-event/8000

a=fmtp:101 0-15

---

 

The configurations on CUCM also appear fine and the fact that calls for the same settings via a softphone work but not for the Ricoh MFD, makes me suspect whether it is the Ricoh MFD which supports PCMA or not.

 

Am I missing something?

1 REPLY 1
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Was this working before? 
call and fax work entirely different way. If you make calls and if working you cannot assure that fax will work.

 

in my region  if I use T.38 protocol fax will not work. I need to use g711 pass through to make fax working. 

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