How are IP addresses assigned? What if someone from USA and someone from Australia connected to the internet at the same time - how would they not have the same IP address?
Because public IP addresses are not picked at random, they are allocated by your Internet Service Provider; who in-turn gets a block assigned to them from the next level, and so on to IANA/ICANN.
You might think of this private IP address as a local reference (like, take that left on the next block to reach the cake shop?) for your home router to find your machine in the home network.
If you tried to use a 'public' IP address at random, the ISP will not accept it and you will see no network connectivity.
The assignment of addresses is managed in a hierarchal fashion. At the top of the chain is
They are responsible for the global pool from which they allocate blocks to the
who are responsible for specific regions of the world. They in turn, allocate from their blocks, to the
or if you prefer Internet Service providers.
Because of the way the address blocks are allocated every global Internet address is unique.
IP addresses are assigned by ICANN, so that won't happen. But there's also a more fundamental reason. IP addresses are used for routing. When a packet comes into a router, it compares the IP address against entries in its routing table, and sends the packet on through the appropriate outgoing line. So IP addresses aren't just arbitrary numbers that are assigned - they are meaningful addresses.
protected by Community♦ Feb 3 '15 at 9:38
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