127.0.0.1 is the standard IP address used for a loop back network connection.
This means that if you try to connect to 127.0.0.1 you are immediately looped back to your own machine.
127.0.0.1 is also referred to as “local host” meaning this computer 127.0.0.018 this block is assigned for use as the internet host loopback address.
A datagram sent by a higher level protocol to an address anywhere within this block should loop back inside the host.
Making connection with 127.0.0.1 loop back address is the same as making a connection with any remote computer on the network.
It is widely used by application developers and system administrators with the intension of testing software.
Next address 0.0.0.0
0.0.0.0 is used for default network.
If you use it as static router than it generates a default network.
When used with mask of 0.0.0.0 it matches any address and when used with 255.255.255.255 it matches none. So based on the mask an thing between 0.0.0.0 and 255.255.255.255.