**127.0.0.0/8:** Loopback addresses. 127.0.0.1 (localhost) is the most commonly used. - **169.254.0.0/16:** Link-local addresses (APIPA). If a host cannot obtain an address via DHCP, it will auto-assign an address in this range. Finding these addresses during a scan indicates DHCP issues. - **0.0.0.