IP Address

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Contents 1 Introduction 2 Address Structure 2.1 IPv4 2.2 IPv6 3 Types of Addresses 3.1 Private IP Addresses 3.1.1 Private Address Ranges 3.1.2 Zeroconf/APIPA 3.2 Public IP Addresses 4 Assignment 5 See Also

Introduction

An IP Address is a number uniquely identifying a computer on a given IP-based network. Similar to a phone number in function, it is used by networked devices to find and communicate with other devices - both on the local network or the Internet.

Address Structure

IPv4

The current standard used for addressing on IP-based networks, these addresses are 32-bit integers (ie a real number between 0 and 4,294,967,295). To enhance readability, this is broken up into four 8-bit integers (ie real numbers between 0 and 255) seperated by decimal points. Each of these numbers is typically referred to as an 'octet'.

IPv6

An upcomming standard that expands the length of the address to 128-bits in response to potential address shortages imposed by the earlier standard. While not widely in use at this stage, it is being phased in and will eventually take the place of IPv4 addresses.

Types of Addresses

Private IP Addresses

Private IP Addresses are blocks of addresses that have been reserved for use within private networks. Akin to an extension on an internal phone system, these addresses are used to communicate with other devices connected to the same group of networks. In order to access the Internet, all traffic from devices using private IP Addresses must go through some form of address translation (eg NAT).

It is important to note that the IP Address used by a device must be unique on the network. That is, if a laptop is configured to use the address 192.168.0.100 then no other device (computer, camera, router, etc.) can use that address at the same time. When manually specifying addresses, it is often a good idea to record which addresses have been used for which device in order to avoid conflicts.

Zeroconf/APIPA

Another block of private IP Addresses has been set asside for use by automatic addressing systems where no DHCP server is present. By convention, these addresses are not typically used when manually setting up a network. The APIPA (Automatic Private IP Addressing) range is as follows:

Address Range			Subnet Mask	Example
169.254.0.1	-	169.254.255.254	255.255.255.0	169.254.238.142

Public IP Addresses

Public IP Addresses are those used by devices that are exposed to the Internet. These addresses are similar to an international phone number - they provide a unique identifier that allows any other device connected to the Internet to find and communicate with the device(s) using it.

Unlike private addresses, users must use addresses that have been uniquely assigned to them by ICANN (Internet Corporation for Assigned Names and Numbers) and its member bodies. Typically this process is handled through ISPs, who are assigned blocks of addresses and distribute them amongst their clients as needed.

Assignment

Typically, IP Addresses are automatically assigned by a DHCP server located in a router on the network. This device maintains a table of available addresses and will automatically provide all of the necessary settings to any device that is connected to the network. This greatly simplifies the process for many users, as it shields them from the underlying complexity of the system.

For networks without DHCP servers, these addresses must be entered manually. If operating on someone else's network, users should always consult the appropriate administrators for the correct settings to avoid any conflicts.

When setting up a small network without a router, however, it may be necessary to manually assign addresses. In these scenarios, here are a few simple guidelines for setting things up:

• Use addresses from one of the designated private address ranges. For small networks, using addresses in the 192.168.0.10-192.168.0.254 range is generally recommended.
• Each device on the network must be given a unique address. Assigning the same address to two devices will cause a conflict and neither will be able to communicate.
• Generally, the first three numbers in the IP Address should be kept the same and only the last number changed. See the subnet mask article for more information.

If working with devices that are directly attached to the Internet, users must talk to their ISPs to be assigned appropriate addresses. As noted above, public addresses are governed by a central body so the use of assigned addresses is necessary for proper operation.

See Also

• DHCP - Protocol used for automatic assignment of IP network settings.
• Subnet Mask - A network setting used to determine which portions of the IP Address are used for various functions.
• Router - A networking device used to interconnect various networks together in a controlled fashion.
• DNS - Protocol used to translate domain names into their respective IP Addresses.