Exam 350-801 topic 1 question 377 discussion

A. is incorrect. Wheter or not auto-reg is enabled, it does not matter. B. is incorrect. It is a application problem, it is not a layer 2 problem. D. Is incorrect. I MAC is wrong, in the CUCM just appear as "none". And if the MAC is duplicated, CUCM does not allow you to save it. So, C . is the most rational answer. The engineer did something wrong with the phone and lastly affected the ITL in the phone.

it says a new phone so don't think B is correct

https://community.cisco.com/t5/unified-communications-infrastructure/ip-phone-registration-status-shows-quot-rejected-quot-in-call/td-p/2873968 "This is expected as security by default feature will prevent a phone previously registered to one cluster from registering to another cluster without deleting the ITL certificates from the phone which factory reset does for you"

A is the correct answer. The phone cannot have a certificate since it has never register to the CUCM. It gets the cert at 1st registration. In addition the "Rejected" error message occurs when trying to register and auto registration is disable.

I think the best answer here is C: A. whether auto-registration is enabled in Cisco UCM - Auto reg isn't mentioned and is not required for a manually configured phone to register. B. whether the phone is in the correct VLAN - If the phone is rejected it was able to communicate with the CUCM and attempt to download it's configuration indicating there is not a network issue with connecting to TFTP or the CUCM. C. whether the Initial Trust List and Certificate Trust List files on the phone are correct - An expired ITL or an ITL from a different server will cause a Rejection. D. whether the phone’s MAC address is correct in Cisco UCM - If the MAC was incorrect it would not show rejected, it would show as none or unknown. The MAC has to be right for it to get rejected in the first place.