Addressing

Back What is an IP ADDRESS? An IP address is a number that is used to identify a device on the network. Each device on a network must have a unique IP address to communicate with other network devices. As noted earlier, a host is a device that sends or receives information on the network. Network devices are devices that move data across the network, including hubs, switches, and routers. On a LAN, each host and network device must have an IP address within the same network to be able to communicate with each other. A person's name and fingerprints usually do not change. They provide a label or address for the physical aspect of the person – the body. A person's mailing address, on the other hand, relates to where the person lives or picks up mail. This address can change. On a host, the Media Access Control (MAC) address (explained below) is assigned to the host NIC and is known as the physical address. The physical address remains the same regardless of where the host is placed on the network in the same way that fingerprints remain with the person regardless of where the person goes. The IP address is similar to the mailing address of a person. It is known as a logical address because it is logically assigned based on the host location. The IP address, or network address, is based on the local network and is assigned to each host by a network administrator. This process is similar to the local government assigning a street address based on the logical description of the city or village and neighborhood. An IP address consists of a series of 32 binary bits (ones and zeros). It is very difficult for humans to read a binary IP address. For this reason, the 32 bits are grouped into four 8-bit bytes called octets. An IP address, even in this grouped format, is hard for humans to read, write, and remember; therefore, each octet is presented as its decimal value, separated by a decimal point or period. This format is referred to as dotted-decimal notation. When a host is configured with an IP address, it is entered as a dotted decimal number, such as 192.168.1.5. Imagine if you had to enter the 32-bit binary equivalent of this: 11000000101010000000000100000101. If just one bit were mistyped, the address would be different and the host might not be able to communicate on the network.

The logical 32-bit IP address is hierarchical and is composed of two parts. The first part identifies the network, and the second part identifies a host on that network. Both parts are required in an IP address. As an example, if a host has IP address 192.168.18.57, the first three octets, 192.168.18, identify the network portion of the address, and the last octet, 57 identifies the host. This is known as hierarchical addressing, because the network portion indicates the network on which each unique host address is located. Routers only need to know how to reach each network and not the location of each individual host.  **IP addresses are divided into the following five classes: **
 * Class A – Large networks, implemented by large companies and some countries
 * <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-list: l0 level1 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; tab-stops: list .5in; text-align: justify;"><span style="font-family: 'Georgia','serif'; font-size: 12pt; line-height: 150%;">Class B – Medium-sized networks, implemented by universities
 * <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-list: l0 level1 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; tab-stops: list .5in; text-align: justify;"><span style="font-family: 'Georgia','serif'; font-size: 12pt; line-height: 150%;">Class C – Small networks, implemented by ISPs for customer subscriptions
 * <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-list: l0 level1 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; tab-stops: list .5in; text-align: justify;"><span style="font-family: 'Georgia','serif'; font-size: 12pt; line-height: 150%;">Class D – Special use for multicasting
 * <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-list: l0 level1 lfo1; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; tab-stops: list .5in; text-align: justify;"><span style="font-family: 'Georgia','serif'; font-size: 12pt; line-height: 150%;">Class E – Used for experimental testing



<span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; text-align: justify;"> Subnet Mask <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; text-align: justify;"><span style="font-family: 'Georgia','serif'; font-size: 12pt; line-height: 150%;">The subnet mask indicates the network portion of an IP address. Like the IP address, the subnet mask is a dotted decimal number. Usually all hosts within a LAN use the same subnet mask. Figure 1 shows the default subnet masks for usable IP addresses that are mapped to the first three classes of IP addresses:
 * <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-list: l1 level1 lfo2; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; tab-stops: list .5in; text-align: justify;"><span style="font-family: 'Georgia','serif'; font-size: 12pt; line-height: 150%;">255.0.0.0 – Class A, which indicates that the first octet of the IP address is the network portion
 * <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-list: l1 level1 lfo2; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; tab-stops: list .5in; text-align: justify;"><span style="font-family: 'Georgia','serif'; font-size: 12pt; line-height: 150%;">255.255.0.0 – Class B, which indicates that the first two octets of the IP address is the network portion
 * <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-list: l1 level1 lfo2; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; tab-stops: list .5in; text-align: justify;"><span style="font-family: 'Georgia','serif'; font-size: 12pt; line-height: 150%;">255.255.255.0 – Class C, which indicates that the first three octets of the IP address is the network portion

<span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; text-align: justify;"><span style="font-family: 'Georgia','serif'; font-size: 12pt; line-height: 150%;">If an organization owns one Class B network but needs to provide IP addresses for four LANs, the organization must subdivide the Class B address into four smaller parts. Subnetting is a logical division of a network. It provides the means to divide a network, and the subnet mask specifies how it is subdivided. An experienced network administrator typically performs subnetting. After the subnetting scheme has been created, the proper IP addresses and subnet masks can be configured on the hosts in the four LANs. These skills are taught in the Cisco Networking Academy courses related to CCNA-level networking skills. <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; text-align: justify;"> Manual Configuration <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; text-align: justify;"><span style="font-family: 'Georgia','serif'; font-size: 12pt; line-height: 150%;">In a network with a small number of hosts, it is easy to manually configure each device with the proper IP address. A network administrator who understands IP addressing should assign the addresses and should know how to choose a valid address for a particular network. The IP address that is entered is unique for each host within the same network or subnet. <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; text-align: justify;"><span style="font-family: 'Georgia','serif'; font-size: 12pt; line-height: 150%;">To manually enter an IP address on a host, go to the TCP/IP settings in the Properties window for the NIC. The NIC enables a computer to connect to a network using a MAC address. Whereas the IP address is a logical address that is defined by the network administrator, a MAC address is "burned-in" or permanently programmed into the NIC when it is manufactured. The IP address of a NIC can be changed, but the MAC address never changes. <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; text-align: justify;">

<span style="font-family: 'Georgia','serif'; font-size: 12pt; line-height: 150%;"> <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; text-align: justify;"><span style="font-family: 'Georgia','serif'; font-size: 12pt; line-height: 150%;">The main difference between an IP address and a MAC address is that the MAC address delivers frames on the LAN, while an IP address transports frames outside the LAN. A frame is a data packet that, along with address information, is added to the beginning and end of the packet before transmission over the network. After a frame is delivered to the destination LAN, the MAC address delivers the frame to the end host on that LAN. <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; text-align: justify;"><span style="font-family: 'Georgia','serif'; font-size: 12pt; line-height: 150%;">If more than a few computers comprise the LAN, manually configuring IP addresses for every host on the network can be time-consuming and prone to errors. In this case, the use of a Dynamic Host Configuration Protocol (DHCP) server would automatically assign IP addresses and greatly simplify the addressing process. <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; text-align: justify;"> <span style="display: block; line-height: 150%; margin: 0in 0in 10pt; mso-margin-bottom-alt: auto; mso-margin-top-alt: auto; text-align: justify;"> <span style="font-family: 'Comic Sans MS',cursive; font-size: 14pt;">Summary


 * <span style="font-family: Georgia,serif; font-size: 120%;">IP address is unique number which every network device must have. It used to connect with other devices.It contain of two parts. The first part is for the network and the second part is for the host(ex. printer). The IP address includes five categories of class: Class A, B, C, D and E.IP address is different from MAC adress. For example, IP address show the physical address of the network unlike MAC address doesn’t show the address of the network.Also, IP address can be changed but the MAC address cannot be changed.

<span style="font-family: 'Comic Sans MS',cursive; font-size: 12pt;">Resources

<span style="font-family: Georgia,serif; font-size: 120%;">Cisco Networing Academy website