How does Cisco NAC change your DHCP IP

When implementing NAC you may wonder how it changes your IP when you move back and forth betwen the untrusted and trusted VLANs. Back in the olden days, the only way to do this was to bounce the switch port. This caused the link to go down on the connected computer which kicked off a new DHCP request. Nowadays there's a method that works better when the switch port has an IP phone and a computer on the same