Link-local addresses
IP addresses that only work within a single network segment — IPv4 169.254.0.0/16, IPv6 fe80::/10. Auto-assigned when DHCP fails.
IPv4 link-local is called APIPA (Automatic Private IP Addressing) on Windows. Symptom: you get 169.254.x.x when the DHCP server is offline. IPv6 link-local is always present (even when you have global addresses) — for Neighbor Discovery, routing protocols. mDNS/Bonjour uses link-local for "raspberrypi.local" names. Not routable — each interface might have the same address.