Upgrading Old Versions of Communications Manager and Phones

This is a problem you'll encounter when either upgrading an old install of Communications Manager (usually versions prior to 6) or plugging in an old phone that was found in a store cupboard somewhere...


Both SCCP & SIP firmwares for 7900 series phones prior to 8.3.3 can't be directly upgraded to newer versions, it'll usually give an error message along the lines of "auth fail" when the phone tries to download the newer firmware. The solution is to upgrade the phone to 8.5.2, then you can upgrade to any newer firmware. To do this I have a UC540 configured with 8.5.2 firmware loads for most models of phone, then it's just a case of plugging the old phone into the UC540 to do the interim upgrade before connecting it to the live Communications Manager.
You can check a phone's firmware version by going to Settings > Model Information, the version is listed under Load File.