All IP addresses on a network must be unique. This includes network cards, routers and access points. If a network device is on the LAN, then its IP address must be unique on the LAN. If it is connected to the internet, then it must be unique on the internet. Problems with duplicate IP addresses can range from receiving error messages informing you of the existence of duplicate IP addresses to not being able to connect to the network from the device with duplicate address.
Obviously, the use of DHCP, in which assignment of IP addresses is managed by the DHCP server, and IPv6, which has a greater number of private addresses to assign, greatly cuts down on the possibility of duplicate IP addresses. Duplicate addresses ...
