PCs and other client devices normally show an address of 0.0.0.0 when they are not connected to a TCP/IP network.
A device may give itself this address by default whenever they are offline. It may also be automatically assigned by DHCP in case of address assignment failures. When set with this address, a device cannot communicate with any other devices on that network over IP.
0.0.0.0 can also theoretically set as a device's network (subnet) mask rather than its IP address. However, a subnet mask with this value has no practical purpose. Both the IP address and network maskare typically assigned as 0.0.0.0 on a client together.
more info https://en.wikipedia.org/wiki/0.0.0.0