Lan IP

In XP when changing between admin and user accounts with the "switch
user" option, I am assigned a different local IP depending on what user
or admin account I am logged into. How does the hardware recognize the
difference between user A and user B to do this? Is this done at the AP
router or within windows itself?

In Win XP if you change between administrator and user accounts with the
switch_user option, you see a different local IP assigned dependent on
what user or admin account is logged in. How does the hardware/system
identify the difference between user A and user B to do this? Does the
AP router assign the local IP or is this done within windows itself?