Although the Wiznet Ethernet Featherwing, is shipped with a unique
Adafruit MAC address, there is no way to use it or enter it with
Circuit Python. As a result, the Wiznet chip makes up a random MAC
address every time it is initialized, and gets a different DHCP
assigned IP address, hopping up and down the user's network address
space.

The initialization of the wiznet.WIZNET5K() class should provide for
a parameter of the desired MAC address, to be loaded into the Wiznet
chip before the DHCP process is started. This exists in the Arduino
implementation, but not Circuit Python.

There are multiple network side effects and potential problems from
this kind of random MAC address hopping.