My IP Number

How do I find my IP address?

What is my IP Address?

The IP Address of this machine is:

This address can also be represented as 751998725 (32 bit decimal number) or 0x2CD29705 (32 bit hexadecimal number).

(NB - if you are part of an internal network then this is the IP address of your local server, the machine which is connected to the external internet.)

What is an IP Address?

'IP' (Internet Protocol) is the method used for sending and receiving information over the Internet. Any device that is required to communicate over the Internet is assigned a 32-bit number, its IP address, which uniquely identifies it to other devices. The IP address is usually written as a set of four numbers in the range 0-255 separated by dots, although it can also be shown as one big number in decimal or hexadecimal.

How are IP addresses used?

Whenever data is to be transmitted to a particular machine, it is broken up into chunks, or packets, each of which is tagged with the IP address of the destination machine. Each packet is transmitted separately, and will not necessarily follow the same route through the network as the other packets that make up the whole message. It is quite possible that the packets will arrive out of sequence, or with errors. Some may not even arrive at all.

On receipt the packets are automatically reassembled into the correct sequence so as to reconstruct the original data; if there are any errors or missing packets then they are requested to be sent again.

Private IP Addresses

Three ranges of IP numbers are reserved for local or private IP addresses - these are addresses which identify a device on a local network which is isolated from the internet by a router with Network Address Translation.

The three ranges are:

These addresses are never used on the public internet. Typically, behind a NAT device, a sub-range from one of these ranges will be used to identify devices on a local network.

How are IP Addresses Assigned?

IP Addresses are hierarchical in nature - that is to say, one part of the IP address will specify broadly in which region of the network the destination can be found, with subsequent parts of the address providing more specific information about the location of the target device within that region. Consequently the allocation of IP addresses needs to be carefully managed, in order to maintain this hierarchy.

The allocation is overseen by the Internet Assigned Numbers Authority (IANA) and Regional Internet Registries (RIRs), who maintain a publicly accessible database called WHOIS, relating IP Numbers to locations in the network.

What is IPv6?

An IP address as described above is made up of four bytes, in a format known as IPv4. Four bytes can be used to represent over four billion different individual addresses, which might seem sufficient to uniquely label every computer in the world - but with more and more devices being connected to the internet the number of IPv4 addresses which are free to be allocated is dwindling.

IPv6 mitigates this problem by using sixteen bytes instead of four, which allows approximately 3.4x1038 unique addresses to be represented. In addition, the standard solves various other technical problems that IPv4 suffers from.

Unfortunately IPv6 is not interoperable with IPv4, so in order to use it all the internet hardware between IPv6 nodes will need to be updated to be able to use IPv6. Until that happens an IPv6 network is effectively invisible to IPv4 systems, and vice versa, although it is technically possible to implement converter nodes that embed one protocol within the other to allow connections between the different networks.

Who owns an IP Address?

Whilst you may not be able to track an owner of an IP address, you can usually find out its location. If you know the IP address, enter it on this free tool: ip lookup - also known as IP Geolocation - GeoIP.

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