So, What is an IP Address?

IP ADDRESSING

To route “packets” or information over a network an IP address is used.  The TCP/IP protocol is the most commonly used protocol to transmit and receive information over a network.  An IP address is a unique, 32-bit, logical number.  The IP Address is much like a postal address because it identifies a location, in this case, the location of a device on a network – ensuring that data is sent to the correct location.  But, computers can only process data that is represented in a binary format.  Binary digits, or bits, are ones and zeros that represent two possible states of an electric impulse.  Below is an example of an IP address converted to a 32-bit binary number.

10101100000100001000000000010001

IP addresses are usually represented in decimal format as four sets of “octets” because it’s simply easier to remember. (1 octect = 8 bits)  Each binary digit has a corresponding decimal position value.

Let’s use this binary containing 32 bits as an example:  10101100000100001000000000010001

Divide it into four octets.

Remember, 1 octet equals 8 bits.  So, the first octet would be 10101100, the second octet is 00010000, the third octet is 10000000, and the fourth octet is 00010001.

Convert each octet into a decimal.

You convert each octet into a decimal number. To learn how to do this Click Here.  Each decimal number ranges from 0 to 255.  If properly converted, you should get 172 16 128 17.

Seperate each octet by a period.

Even though an IP address is a 32-bit address.  The address is written in dotted decimal notiation by seperating each octet with a period.  In this case, you come up with 172.16.128.17

An IP address has two parts:

• Network ID
• Host ID

The Network address, or network ID, is the address of the network the device is located on.  The network ID part of the address always contains at least the first “octet”.  The host ID is the host address.  The host ID part of the address always contains the last octet of the address.

Many computers may share the same network ID, but, combining the network ID with a host ID uniquely identifies an device connected to the network, or the IP address.

If you’ve heard of IP addresses, you might have also heard of subnets.

What is a subnet?

Large networks are often broken down into divisions, or sub-networks (subnets).  Subnets are created for many reason including:

• network traffic control
• use of different physical media
• greater security
• addressing flexibility

Traffic control is a common reason for creating subnets because network performance can suffer as a result of heavy traffic.  During busy times, collisions can occur and impair the network’s performance.  Breaking the network down into subnets helps prevent this from happening.

Routers are common devices used to break networks down into subnets.  A router is assigned to a particular subnet and deals with data packets relating only to that particular subnet, passing on any other data with a different subnet address to another router on the network.

Each subnet is assigned an address based on the IP address of the network.  For example, a network with the IP address 172.16.0.0 is broken down into subnets 172.16.1.0, 172.16.2.0, 172.16.3.0, and so on.

Subnet addresses are created from the host number portion of a Class A, Class B, or Class C address.  Subnet addresses, like IP addresses, must be unique.  This leads us to subnet masks

Subnet Masks

A subnet mask is a 32-bit address divided into four 8-bit octets, much like the IP address.  Used with the IP addresses, it determines the network where the subnet is based and indentifies the subnet and the host.

The default subnet masks are:

• Class A
• Class B
• Class C

The Class A network uses the default subnet mask 255.0.0.0  This mask comprises 8 network bits and 24 host bits.

The Class B network uses the default subnet mask 255.255.0.0  This mask comprises 16 network bits and 16 host bits.

The Class C network uses the default subnet mask 255.255.255.0  This mask comprises 24 network bits and 8 host bits.

Default Gateway

Simply put , the default gateway is an IP address that specifies the entry and exit point from in a network.  It is a “border service” used by the host when an IP packet is destined for a location outside of the local subnet.  Typically, your router is the default gateway.

To function properly, some networks require additional services such as DHCP and WINS

DHCP

DHCP, or Dynamic Host Configuration Protocol, leases IP addresses from a scope that has been defined for each subnet.  This method is used with the clients, or nodes, on the network do not require a fixed IP address and administration is greatly reduced.

WINS

WINS, or Windows Internet Name Service, provides name resolution services to support what is called NetBIOS over TCP/IP networks.  Microsoft operating systems built prior to Windows 2000 use NetBIOS and requires WINS for name resolution services.  Many applications still run over NetBIOS and also need access to WINS.  In these cases a WINS server is required.

While many average users will not need to configure IP addresses, knowing how IP addresses work  can be important when attempting to set up your own network.