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Cisco Bug: CSCuq44635 - CUCM sends Maxbitrate=0 causing fax failure

Last Modified

Feb 02, 2017

Products (1)

  • Cisco Unified Communications Manager (CallManager)

Known Affected Releases


Description (partial)

IMS (PSTN)-------ASR------SIP-------CUCM 9.1(2)------SIP--------VG204---------FAX
T.38 fax call fails. 
Incoming call from PSTN  to loca fax connected to VG2xx
Voice call is established OK 
Then when the T.38 fax tone is detected, the VG will send a RE-INVITE with T.38 capabilities 
As soon as this dialog is confirmed with 200 OK from CUCM , the VG204 disconnects the call. (immediately after receiving the 200 OK from CUCM)
The reason why the VG disconnects is b/c of this: 
VG sends a RE-INVITE towards CUCM (when it detects the fax tone) containing the maxbitrate=14400 parameter. 
CUCM sends this on to the aggregation. 
In this case, the aggregation responds without this parameter in its 200 OK response.   CUCM in turn sends maxbitrate=0 parameter to the VG. 
The VG does not like this and fails the call.

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