Faxing and CenturyLink SIP Trunks ----- ITSP - SIP - CUBE - SIP - CUCM - SIP - VG224 - FAX

[asafayan1]

I've inherited an environment with about 30 Konica-Minolta MFPs with faxing.  Our monthly recurring telco costs for the analog lines are approx. 2,000 / month.  I'm hoping to get real customer input as to how they have eliminated their dependency upon analog lines and migrated to FoIP.  I'm not interested in RightFax or other fax server or cloud faxing solutions as we have a very high fax volume that excludes those solutions.

We have CenturyLink SIP trunks and I'm hoping to build out this fax call flow:

ITSP - SIP - CUBE - SIP - CUCM - SIP/H323/MGCP/SCCP - VG224/ATA - FAX Machine

My questions are:
1. What model Voice Gateway or ATA and what call control protocol are you using for your Voice Gateways to attach to your fax machines?

2. Have other enterprises using CenturyLink SIP trunks successfully implemented Fax Pass-Through to migrate from analog lines to FoIP?

[Chris Deren · Accepted solution]

Any Cisco analog gateways such as VG20X, VG224, VG310, VG320, VG450, etc. support both pass-through and T.38. For protocol based T.38 you can use MGCP, SIP or H323, but not SCCP. For pass-through any protocol works.

Many organizations use FoIP over SIP trunking, and if configured correctly end to end (CUBE and analog VG) it works fine. I have done it with CentryLink and it worked fine with pass-through as long as you setup end to end G711.

[asafayan1]

Thanks Chris.

From this doc - https://www.centurylink.com/business/help/voip/equipment/using-a-fax-machine-with-voip.html

It appears that CenturyLink only supports fax pass- through and only support Super G3.  

Based on your experience, have you found that you have to disable Super G3 and ECM? 

Best,

Amir

[Chris Deren · Accepted solution]

I don't think SG3 speeds are supported by pass-through on Cisco IOS, I believe only Protocol-based T.38 version 3 and passthrough (NSE based) support SG3 speeds. This is very good document on faxing over IP in cisco:

https://www.ciscolive.com/c/dam/r/ciscolive/us/docs/2018/pdf/BRKUCC-2021.pdf

Chris