With DNS, what does 0.0.0.0 stand for?
I have it set (Network and sharing settings → change adapter settings → Wireless network connection → Internet protocol v4 → Use the following DNS settings) to 0.0.0.0 but what do those numbers represent?
62 Answers
Because 0.0.0.0 is not a valid destination address, this is simply an invalid configuration.
DNS servers, like other regular IP services, need to be addressed by a valid destination IP address, ie. anything but 0.0.0.0 and 255.255.255.255 minus a few reserved ranges. Depending on the actual network configuration, other addresses might be invalid, too, like 192.168.2.0 and 192.168.2.255 on the 192.168.2.0/24 network.
Additionally, for name resolution to work, the server has to be reachable.
There is one valid use for the 0.0.0.0 address though: When listening for connections, it means “listen on all interfaces on this computer”.
Some programs may erroneously display 0.0.0.0 where a value is not set.
Windows (8.1 in my case) will also prevent you from entering a 0 octet in the first group of an IP address.
The IPv4 address 0.0.0.0 usually represents an unknown address, in instances where an address must be specified.
It makes a good placeholder in cases where an IP address must be specified but none is yet known. It is not supposed to be seen on the wire (or on the air) after DHCP IP autoconfiguration completes. The reason why you see it is likely that you have explicitly said that you will specify the DNS server IP addresses yourself, but have not yet specified the addresses to any DNS servers.
