[cisco-voip] SIP trunk fax troubleshooting

[Robert Kulagowski]

Outbound faxes aren't working.

Fax machine is connected to a VGC -> CUCM -> SIP trunk -> CUBE -> bandwidth.com

Cisco IOS Software, C2900 Software (C2900-UNIVERSALK9-M), Version
15.1(4)M2, RELEASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2011 by Cisco Systems, Inc.
Compiled Mon 26-Sep-11 17:37 by prod_rel_team

ROM: System Bootstrap, Version 15.0(1r)M12, RELEASE SOFTWARE (fc1)

voice service voip
 ip address trusted list
  ipv4 216.82.224.202
  ipv4 216.82.225.202
  ipv4 10.255.23.7
  ipv4 10.255.1.21
  ipv4 10.255.29.20
 address-hiding
 mode border-element
 allow-connections sip to sip
 no supplementary-service sip moved-temporarily
 no supplementary-service sip refer
 fax protocol pass-through g711ulaw
 sip
  header-passing
  error-passthru
  no update-callerid
  early-offer forced
  midcall-signaling passthru
  privacy-policy passthru
  g729 annexb-all

dial-peer voice 10000 voip
 description Outbound SIP to Bandwidth.com
 translation-profile outgoing SIP-OUT
 destination-pattern 8T
 session protocol sipv2
 session target ipv4:216.82.224.202
 voice-class sip dtmf-relay force rtp-nte
 dtmf-relay rtp-nte
 codec g711ulaw
 fax-relay ecm disable
 ip qos dscp cs5 media
 ip qos dscp cs4 signaling
 clid restrict
 no vad

The CUBE book makes it seem like it should "just work".

I've also tried:

dial-peer voice 10000 voip
 description Outbound SIP to Bandwidth.com
 translation-profile outgoing SIP-OUT
 preference 1
 destination-pattern 8T
 session protocol sipv2
 session target ipv4:216.82.224.202
 voice-class sip dtmf-relay force rtp-nte
 dtmf-relay rtp-nte
 codec g711ulaw
 fax-relay ecm disable
 fax rate 9600
 fax protocol pass-through g711ulaw
 ip qos dscp cs5 media
 ip qos dscp cs4 signaling
 clid restrict
 no vad

No joy there either.

Seems like fax and modem are perpetual issues with SIP trunking from
what I can see in the archives? The easiest would be to just continue
to send fax to PRI / analogs, but where's the fun in that?