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Faxing Question - Fax - VG224 - CUCM v11.5 - SIP Trunk - PSTN



My org has about 40 Konica Minolta MFPs with fax boards.  These attach to traditional analog lines with monthly recurring costs of about 2,000 USD.  I would like to eliminate the analog lines and attach to a VG224. I used to support multiple VGs for faxing  some 10 years ago and I'm pretty certain at that time they were MGCP configured and my org had T1 lines to the PSTN. 


Currently we have CenturyLink SIP trunks to the PSTN.  My question is - if I try this topology:

Traditional fax < - > VG224 <-> CUCM v11.5 <-> SIP Trunk <-> PSTN 


Can I do this and NOT run T.38 ? Our fax volume is approx. 125,000 in/out pages per month and I have zero time or interest in troubleshooting compatibility issues with T.38.  








You CAN but you SHOULDN’T. Check with the carrier to be sure but most SIP providers only support faxing over T.38. None of them support SuperG3 by the way, T.38v3 or otherwise. Fax relay is also FAR more stable when configured properly (eg fax nsf 000000, LS/HS redundancy, etc). Yet another difference to consider with SIP to the carrier is Cisco fax passthrough won’t actually work: the provider won’t acknowledge the proprietary NSE to complete switchover (eg disable EC, raise dejitter buffer, upspeed, etc). Without T.38 you’re running as a straight G.711 voice call. I can’t imagine a more fragile fax config.. well, short of connecting the VG using a 2.4 GHz WifFi bridge!

One compromise you could consider is an ISDN circuit instead of SIP if you are concerned about it; a PRI should be cheaper than 40 analog loops. Still, I would run T.38 internally on the VoIP portion of that design.

A plug for the excellent Cisco Press book Fax, Text and Modem Relay here; it remains the bible on this topic.


PS- 125k pages per month duty cycle?! That’s roughly 156 pages per machine per weekday! Have you considered a proper fax server? I’m a big fan of XMediusFAX.

What a blessing you are Jonathan to not just me - but the community at large.  I'm old enough to remember when I used to yearn to know what other Cisco client's are doing in their environments ( pre Cisco Community forum days ) and here we are with folks like you, Deji and so many others who share their knowledge!


Could you PM me to discuss your availability to consult on this project for my org?  We are the largest privately owned multi-specialty medical practice in Colorado.  As you probably know, med orgs are attached at the hip to fax transmissions.  We are no different.  






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