Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

FAX Error

The configuration below is for SIP Trunk, but having issues with Faxing. It dials fine, but then sender receives an error, and it doesn't even get connected.

Can someone shed some lights.


See Attached Config


Re: FAX Error

Use the following debug commands for verification.

debug fax relay t30 all

debug vtsp all

debug vtsp vofr subframe 3

Re: FAX Error

Under your sip dial-peers you don't specified a fax protocol transmission method so the voip service voip fax method is use. Nothing is specified in voice service voip and so the default is use:


cisco fa relay for all other platforms

none for the Cisco AS5350, Cisco AS5400, and Cisco AS5850

Does destination sip peer support Cisco fax relay?

If no try to use t38 standard method:

codec g711alaw

fax rate 9600

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback pass-through g711alaw

no vad

If no relay method is supported try to configure pass-through:

codec g711alaw

fax rate disable

fax protocol pass-through g711alaw

no vad

see these commands also:

"bearer-cap speech" command under each voice-port;

"network-clock-select 1 T1 0/0/0" enter this command for each interface that is to receive faxes specifying a different priority;