An IP address, or Internet Protocol address, is a unique address given to a device on a network to allow traffic to be routed to that device. Every computer, printer, server, etc on a network will have it own unique IP address. This can be compared to a real home address, everyone who receives post, like letters or deliveries, needs a home address so that the postman or delivery driver knows where to deliver. This is the same for computers, every computer needs their own IP address so the sender knows where to send their message.
You can get two computers or devices to have the same IP address, but they will be within different networks. Within any home or office, or any LAN, there will be one or more devices that are publicly accessible and the rest will be private. Within most homes, there will be a router, which is the publicly accessible device, and computers or phones that connect to the router which are private devices. This means any message that goes to or from the private devices must go through the network’s router, the public-facing device. Two private devices can have the same IP address as they cannot directly communicate and all communication must go through a public-facing device, which routes the message to the internal private device. This means in two different homes two computers can have the same IP address, but computers in the same home network cannot have the same IP address.
There are two main types of IP addresses, version 4 and version 6 or IPv4 and IPv6. An IPv4 address is 4 numbers between 0 and 255 separated by 3 dots, such as ‘192.168.0.1’ or ‘255.345.65.201’. The numbers in an IPv4 address are called octets as they’re made up of 8 bits. An IPv6 address is represented as 9 groups of 4 digits separated by colons. The difference between IPv4 and IPv6 is that IPv6 address can have numbers and letters, between A and F. An example of an IPv6 address is ‘2001:0db8:85a3:0000:0000:8a2e:0370:7334’, leading zeros in each group can be omitted and any groups of just zero values can be replaced with a double colon. There can only be one double colon in an IPv6 address. The previous address can be changed to look like this ‘2001:db8:85a3::8a2e:370:7334’ notice how the leading zeros have been removed and the groups of just zeros have been replaced with a double colon. Remember there can only be one double colon within an IPv6 address Otherwise it can impossible to tell how many groups of zeros have been replaced with the double colons.
As you can might be able to work out, using either IPv4 or IPv6 there can only be a certain number of possible unique addresses. This is why the new IPv6 was created as the number of unique IPv4 address remaining had run out. IPv4 can have about 4 billion different unique addresses, whereas the IPv6 protocol can have about 340 undecillion unique addresses (that’s the number 340 followed by 36 zeros).