Scenario: Desktop Support moves a phone to a port with the wrong VLan infomation and no option 150, and phone still registers, even on a port with a trunk config for an access point.
A phone that initially registers successfully, and then is moved to another port without option 150 for TFTP, the 8800 phone has the ability to use a pre-stored config and still Register with CUCM.
I am not sure what other model phones have this capability, but the Cons out-weigh the Pros.
P1 - The user is not impacted and has a working phone registered with CUCM.
C1 - Any CUCM phone config changes, phone resets, tries to get config and fails, but does register.
C2 - Any Firmware changes to the Phone would fail.
C3 - Any wallpaper changes to the phone would fail.
C4 - MOH, CUCM Group updates, would fail.
C5 - Phone URLs, Buttons - Messages, Directories, Services, would fail.
C6 - Trust lists and CTL port information updates would fail.
C7 - And any and all TFTP things I am not thinking of would fail.
Seems that the PHONE knows using TFTPCfgStatus
TFTPCfgStatus = 3 Phone did NOT receive a TFTP server from DHCP.
TFTPCfgStatus = 1 Phone successfull TFTP option via DHCP.
Use this Status to put a Red Bar like DND or Stop Registration with an OK button or something so that someone knows the phone is working in a pre-config state and connected to a non voice configured port.
Just because CUCM shows the phone is registered is not necessarily a good thing. Maybe is should say Partial-Register like when it doesn't have a side car and is configured for one.
Maybe its time to even allow a TFTP server option to be added to the device pool, so that if a Phone does manage to register, the Subscriber then tells the phone what TFTP information it needs to know.