New phones on old firmware

[Apersons]

We have a customer still running an old school 3300 controller (pre MXE/CX series) on 4.0 firmware. They have mostly 5224 IP phones with 2 or 3 5324 IP phones on boot load 02.04.something.something.

The last 2 times we have been out, we have tried installing new 5324 IP phones but they are running 06.00.something.something. The attempt today results in getting an L2 DL error and the phone automatically resetting. Even when programming matched existing phones and used in an known working port, kept getting the same error. or would get TFTP svr unavailable error.

Did the latest builds on the phones knock out it's ability to register with older firmware versions? I know phones can upgrade or downgrade to match the boot load. Wasn't sure if the latest versions of phone firmware block older boot loads? or if it's a hardware compatibility problem?

Does anyone have a procedure to manually downgrade phone firmware for just such an occasion?

[acejavelin]

Try erasing the Main Load and booting... You must have option 43 or 128 setup correctly or it won't work. This will erase the main load from the device, and then write it manually from the FTP server. Note that this could brick the phone though, so try one first and be prepared to trash it if it fails.

Hard to say if it will work... I haven't had a Mitel running 4.0 software in over 8 or so years. This software was released in 2009, and support for it ended in January of 2013 when 6.0 was released. You should really get this one upgraded to 8.1 at least.