DNS Reservation error: The Unique Identifier you have entered may not be correct. Do you want to use this Identifier anyway?

This is more of an annoyance than an actual issue.

At the time of DNS reservation, I found this error when I am providing perfectly valid MAC address and IP address.

It turns out this is nothing but Windows telling you that it doesn’t like the colon (:) in the MAC address. Removing colons like below get things working perfectly.