Understanding Ip Address - Networking Stuffs

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Understanding the Hierarchical IP Addressing Structure

As mentioned earlier, IP addresses are 32-bit unique identifiers. The bits of an IP address are divided into octets. The notations used to indicate IP addresses are:

    * Dotted-decimal notation
    * Binary notation
    * Hexadecimal notation

The 32-bit IP address is a hierarchical structured address. IP addresses are not flat addresses. IP addresses are considered hierarchical addresses because the address space is divided into ordered chunks. The 32 bits are not in its entirety a unique identifier. A segment of the IP address is the network address, and another segment is the host (node) address. This segregation is what makes IP addresses hierarchical structured addresses.

    * The network address or network ID uniquely identifies a network. All computers and all other devices on the same network, have the identical network address as a segment of their IP address. When using network addresses or IDs, remember the following important rules:
          o Because 127 is reserved for loopback addresses, a network address cannot have 127 as the first octet.
          o All bits of the network ID cannot be set to ones (1s). This is used for broadcast addresses.
          o All bits of the network ID cannot be set to zeroes (0s). This is used to designate the local host.
          o If you have different network segments, each network address has to be unique to the IP address.
    * Each TCP/IP host on the network, such as a server, router or workstation has a uniquely assigned host address (Host ID), or node address. The host address has to be unique so that each machine on the network can be uniquely identified. When using host addresses or host IDs, remember the following important rules:
          o You cannot set all the bits in the host address to all 1s, or to all 0s.
          o A host ID has to be unique in the network that it belongs to.

When the Internet was designed, it was decided to create classes of networks. These classes of networks are based on the size of the network.

    * Class A network: The Class A network was designed for a very small number of networks which have a large number of nodes or hosts.
    * Class B network: The Class B network was designed for networks between very small and very large.
    * Class C network: The Class C network was designed for a very large number of networks that have a small number of nodes or hosts.

The characteristics of the network address classes are listed below:

    * Class A network:
          o Leading bit pattern: 0
          o Decimal Range of first byte of the network address: 1 - 126
          o Maximum number of networks: 126
          o Maximum nodes per network: 16,777,214
    * Class B network:
          o Leading bit pattern: 10
          o Decimal Range of first byte of the network address: 128 -191
          o Maximum number of networks: 16,384
          o Maximum nodes per network: 65,534
    * Class C network:
          o Leading bit pattern: 110
          o Decimal Range of first byte of the network address: 192 -223
          o Maximum number of networks: 2,097,152
          o Maximum nodes per network: 254

Understanding Reserved IP addresses

A few IP addresses are reserved for specific special purposes. The reserved IP addresses are:

    * Network segment of the address specified to zeros/0s: Indicates this network or subnet (local network).
    * Network segment of the address specified to ones/1s: Indicates this network and all associated subnets.
    * Network address 127: The address is reserved for loopback testing.
    * Host address of all zeros/0s: The address is typically used in routing tables, and when referencing a network, but not particular hosts on the network.
    * Host address of all ones/1s: This is used as a broadcast address for all the nodes on a particular network.
    * Full IP address specified as specified as zeros/0s: The address is used by the RIP protocol to specify the default route.
    * Full IP address specified as specified as ones/1s: The address is use to broadcast to all nodes on the current network.

Converting Between the Binary Notation and Decimal Notation

In the dotted-decimal notation, the digits 0 to 9 are used. With the 32-bit IP addresses, the octets and bit places are numbered from the left to the right. Each number in the decimal system can be represented in the binary format. The binary system uses only two digits, which are 0 and 1. A binary digit is called a bit. With IP addressing, an octet is formed by 8 bits. An IP address consists of 32 bits, or four octets.

The initial octet refers to the leftmost octet. The bit places 1 to 8 signify the eight leftmost bit places. The second octet signifies the following eight bits, which is bit places 9 to16. The third octet signifies the following eight bits, which is bit places 17 to 24. The fourth octet signifies the following eight bits, which is bit places 25 to 32.

    * In the dotted-decimal notation, periods are used to divide the four octets.
    * In the binary notation, spaces are used to separate the four octets.

If you want to convert a binary number to a decimal number, add the value of each bit position set to 1. If you want to convert a decimal number to a binary number, determine the largest binary bit represented.
Understanding the Different IP Address Classes

The different IP Address classes are:

    * Class A addresses were created for tremendously large networks with many hosts. With Class A addresses, the first high-order bit is zero.

      The Class A address format is defined below:
          o Network.Node.Node.Node.

      The Class A addresses has the following characteristics:
          o The first 8 bits or octet is the network address.
          o The second octet, third octet and fourth octet defines the host address or ID.
          o The maximum number of Class A networks that can be created is 128, of which only 126 is considered possible useable network addresses. This is due to 127 being defined for loopback testing. In addition to this, all bits of the network ID cannot be set to ones (1s) nor can all bits of the network ID be set to zeroes (0s).
          o There is also a multitude of useable unique host addresses for a Class A network. The precise figure of possible host addresses is 16,777,216. Of this figure, two addresses are considered reserved IP addresses.
    * Class B addresses were created for networks that are medium of size and which have an average number of hosts. With a Class B address, the initial two high-order bits are set to 10.

The Class B address format is defined below:
          o Network.Network.Node.Node.

The Class B addresses have the following characteristics:
          o The first 2 octets define the network address
          o . A Class B network has more network IDs than a Class A network
          o A Class B network has fewer host IDs than a Class A network
          o The third octet and fourth octet defines the host address or ID.
          o The maximum number of Class B networks that can be created is 16,384.
          o Each Class B network can have 65,534 possible host addresses or IDs
    * Class C addresses were created for networks that are small and that have few hosts. With a Class C address, the initial three high-order bits are set to 110.

The Class C address format is defined below:
          o Network.Network.Network.Node.

The Class C addresses have the following characteristics:
          o The first 3 octets define the network address.
          o The fourth octet defines the host address or ID.
          o The maximum number of Class C networks that can be created is 2,097,152.
          o Each Class C network can have 254 possible host addresses or IDs
    * Class D addresses are reserved for multicasting only. The initial four high-order bits are set to 1110, and the last 28 bits are used for multicast addresses. Multicast Backbone on the Internet (MBONE) uses Class D addresses. MBONE is an extension to the Internet that enables a packet to have more than one destination. The Class D addresses utilize the address range 224.0.0.0 through to 239.255.255.255.
    * Class E addresses are reserved for future use, and not supported in Windows Server 2003. The initial five high-order bits are set to 11110. The Class E addresses use the address range 240.0.0.0 to 255.255.255.255.