My situation is a little bit complex, but I’ll give you a simplified, more typical version of it:
my ISP assigns one public IP to my router, which then uses NAT to provide connectivity to the various devices in my home. I have set up port-forwarding on the router to make TCP 4001 and UDP 4001 forward to the same ports on my Mac, which the IPFS daemon uses for communication.
the daemon will announce my public IP along with the TCP and UDP ports, which is what other nodes will use to establish a connection.
on occasion, the IP address changes, but the daemon is able to notice and announce my new address when it happens.