Has anyone successfully upgraded to CUCM 15 with older equipment

[HillyardK]

We have older voice gateways and endpoints that work on 12.5 but Cisco wants us to upgrade to 15.  However 7 days before, someone asked if the iOS on our gateways were updated to the version it needed. 

In all the months of planning, no one made any mention of this.  Has anyone else upgraded their CUCM to 15 with 2900 and 3900 voice routers and 7940/7960s and 7941/7961 phones at a minimum?

If so, what did you have to do to prep and what issues did you end up experiencing?

[Roger Kallberg]

Have you checked the CSR Compatibility matrix?

[Jonathan Schulenberg]

Good grief, that gear is ancient! Cisco has not deprecated additional phone models since 12.0; however, there was mention at Webex One in 2024 that the 7940/7960 are coming precariously close to forcing Cisco's hand. It hasn't happened yet but you'll want to review release notes carefully from here on out.

Generally speaking, it all still works though - especially since the MGCP/SCCP code in CUCM hasn't been touched in quite some time. None of that equipment will have been tested with a current CUCM build though. TAC won't support issues either. It's basically a ship adrift at sea - that hasn't run aground yet. This was equally true with CUCM 12.5 so this shouldn't be a surprise.