What is an IP address?

An Internet Protocol (IP) address is a unique logical numeric address that identifies every device - network node(single computer, printer, switch, router, etc.) that is part of a TCP/IP-based networkThe concept is similar to addresses in a town or city as the IP address gives the network node an address so that it can communicate with other nodes or networks, just like mail is sent to friends and relatives.

There are IP addresses are used by the whole Internet (external IP), and only used by locally (internal IP, (Local Area Network  - LAN IP) when you are using a router for example).

The situation is a bit easier with local addresses (for example computer, printer, smartTV connected to the router), the router/switch assigns internal - Private IPs.

As for external - Public IPs (World Area Network - WAN IP on the external interface), it is a bit more complex: the Internet Service Provider (ISP) assigns the external IPs to devices. It might be nice if every device had its own IP address, it is unfortunately not possible as network devices come and go frequently - millions are added, removed, or rearranged every day. It would be impossible for everyone in the world to keep up with the changes. Another reason that local networks use their own addresses is that the Internet ran out of "regular" IP addresses long ago.

In the above picture, there are three computers in the local network that have each been assigned their own internal IP address by the router. The ISP is connected to the router and gives the router an external IP address that allows it to communicate with the Internet. While on the Internet everyone sees your external IP address, but any information coming from the router is routed from the external IP address to the internal IP address.

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