How does the iPad expose its host name over the network?
Solution 1:
The iPhone can be found by name using Bonjour. The name will be my-ipad.local This name is the name in theIOS device with spaces and some punctuation removes as in @TheX's answer and then local as the domain telling devices to use Bonjour lookup. this name is not held in the router, Bonjour asks devices to call out their name on the network.
Solution 2:
It goes by the phones name, dropping special characters, and spaces become hyphens. So for example my iPhone is named "Joshua's iPhone" (I know real creative).
DHCP sees it as Joshuas-iPhone"
Although I was unable to ping my phone by its name, or IP address, not sure if Apple has blocked a port to make this impossible, never really looked into really...