We have an Older MultiTech FF430 hooked into our Mitel 5000 serving as a fax server - which I have heard is common among Mitel Customers.
The problem we had was that every time we lost power (planned or unplanned) the unit would come back up without Ethernet connectivity - and would require an unplug/replug.
Working with MultiTech support, we finally narrowed it down to setting a fixed port speed of 100M Full Duplex (no auto anything) on both the server and the switch. However, to do this on the server required a Putty SSH connection to the MultiTech since the web interface offered no options on port speed. No way anyone would have known this without engaging their support.
mii-tool gives you your connections and allows you to change the settings.
# mii-tool
eth0: negotiated 100baseTx-FD, link ok
eth1: negotiated 100baseTx-FD, link ok
#
# mii-tool -F 100baseTx-FD
# mii-tool
eth0: 100 Mbit, full duplex, link ok
eth1: 100 Mbit, full duplex, link ok
#
I rebooted the server 4 times after this setting, and it connected to our switch every time. Again, you have to have these settings on both the Fax Server and the switch port that the server is connected to.
Hope this helps anyone dealing with a similar issue.