Zeroconf (Zero Configuration) is the collection protocol used for link-local IP assignment and service discovery. Zeroconf is only used if DHCP is not available, since it is located on clients machine. When DHCP is available again, the Zeroconf releases its assigned IP and uses the one provided by DHCP server.
IPv4LL (IPv4 Link Local) protocol is used for address assignment when computers are locally connected. Newly connected computers in the subnet randomly choose IP from allowed range between 169.254.1.0 and 169.254.254.255. Then they send message to other computers in the network, asking if IP is already in use. If IP is used, the computer that is already using it is broadcasting message indicating that IP cannot be assigned. That makes new coming computer renegade IP and complete procedure again. If the IP is not used by any other workstation, there would be no reply. After there is no reply for some time, newcomming computer would assign itself an IP and broadcast message informing network members that IP has been assigned.
In case if IP has been assigned statically it overwrites any configuration that zeroconf may have done.
Figure 1. Situation where Zeroconf would be applicable.
