In CM, make sure you "add ip-interface procr" and set it to accept H248 gateways. That's how you turn on processor ethernet.
In the gateway:
show mgc list - that'll show where it's registering
clear mgc list - that'll wipe it
set mgc list 1.1.1.1,2.2.2.2,3.3.3.3 - that'll tell the G450 to register to one of those 3 IPs, in that order.
Shared IP processor ethernet means (to me) that you have a duplex pair of CMs - say, 1.1.1.2 and 1.1.1.3 and they share an active IP of 1.1.1.1. Whichever server is in control is handling IP 1.1.1.1.
So, if you had a single gateway with a single server and no survivability going on, and you had a G650 with a CLAN you were registering to before, then following the procedure I outlined above would let you point that G450 to the CM server directly rather than through a CLAN in the G650.