ifconfig -a
            

You would see a minimum of two interfaces, we expect we are going to see Ethernet 0 because we have just configured an IP address on it. Additionally, we will see an Internet address called "lo" and this is the loop back interface. Every network device be it a switch, router, server or a hub, will always have a loop back device associated with it.

And this loop back device will always have the address 127.0.0.1.

Now when we were doing the IP addressing we said that the

Class A networks could range between 1 and 127.

Class B networks could range between 128 and 191.

Class C networks could range between 192 and 224.

Here we have an address 127.0.0.1 - clearly this is an Class A address.

Your loop back interface can never have any other IP address than 127.0.0.1, which means if you are setting up a network it would not make sense to allocate to Ethernet 0 a 127.0.0.1 address because on every network one must have unique IP addresses.

So allocating an IP address of 127.0.0.1 to Ethernet 0 will conflict with the loop back address, which has also got the address of 127.0.0.1.

IP address of hosts on the same network must be unique.

Having said that there is a technique called network address translation or NAT. NAT allows us to translate from one IP address to another, but now is not the time to discuss that.