IP ADDRESSING AND SUBNETTING

IP addressing

IP addresses are used as the address in the relationship between hosts on the internet so it is a universal communication system because it is an addressing method that has been accepted worldwide. By determining the IP address means that we have provided a universal identity for each interadce computer. If a computer has more than one interface (eg using two ethernet) then we must give two IP addresses for each computer for each interface.

2.Format IP Address

IP addresses consist of 32-bit binary numbers separated by a dot every 8 bits. Each 8 bits are called octets. IP address form can be written as follows:

xxxxxxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx

So the IP address has a range of 00000000.00000000.00000000. 00000000 to 11111111.11111111.11111111.11111111. IP address notation with binary numbers like this difficult to use, so often written in the fourth decimal, each separated by 4 pieces point better known as "dotted decimal notation". Each decimal number represents the value of one octet IP address. 

3.Pembagian Class IP Address

The number of available IP addresses is theoretically 255x255x255x255 or about 4 billion more to be distributed to all users worldwide Internet network. The division of these classes are intended to facilitate the allocation of IP addresses, both for the host / network or for certain specific purposes.

IP addresses can be separated into two parts, namely the network (net ID) and the host (host ID). Net ID instrumental in the identification of a network from another network, while the host ID serves to identify a host within a network. Thus, all hosts are connected in the same network have the same net ID. Some of the bits of the early part of the IP Address is the network bits / network number, while the rest is for the host. The dividing line between the network and hosts are not fixed, depending on the class network. IP addresses are divided into five classes, namely class A, class B, class C, class D and class E. The differences of each class is on the size and number. For example class A IP network is used by few but the number of hosts that can be accommodated by each network is very large. Class D and E are not used in general, a class D is used for network multicast and class E for experimental keprluan. Internet Protocol software determines the division of this class by examining the first few bits of the IP Address. Determination of the class is done in the following ways:

• The first bit of class A IP address is 0, with a length of 8 bits net ID and host ID 24 bits long. So the first byte of the IP address class A has a range of 0-127. So in class A there are 127 networks with each network can accommodate about 16 million hosts (255x255x255). Class A IP address given to the network with a very large number of hosts, the IP of this class may be illustrated in the figure below:
• Two bits of a class B IP address is always set to 10 so the first byte is always a value between 128-191. Network ID is the first 16 bits and 16 bits are the host ID so that if any computer has the IP address 167.205.26.161, the network ID and host ID = 167 205 = 26 161. On. Class B IP address has IP range from 128.0.xxx.xxx to 191.155.xxx.xxx, which amounted to 65 255 network by the number of hosts per network host 255 x 255 or about 65 thousand hosts.
• Class C IP address originally used for small networks such as LANs. The first three bits of a class C IP address is always set to 111. Network ID consists of 24 bits and 8 bits of remaining host ID so it can be formed about 2 million networks with each network has 256 hosts.
• Class D IP address used for multicasting. The first four bits of a class D IP address is always set 1110 so the first byte ranges between 224-247, while the next bit is set as required using the IP multicast group address. In multicasting is not known the term network ID and host ID
• Class E IP address is not made ​​available for public use. The first four bits of the IP address of this class is set 1111 so the first byte ranges between 248-255.

In addition the term also known as Network Prefix, which is used to designate the IP address prefix is jaringan.Penulisan network with a slash "/" followed by numbers that indicate the network prefix length in bits. Eg to appoint a class B network 167.205.xxx.xxx used 167.205/16 writing. This is item 16 bits for the network prefix length of class B.

Special 4.Address

In addition to the address used for the host identifier, there are several types of addresses are used for special purposes and should not be used for the host identifier. Address is:

Network Address. Address is used to identify a network on the Internet network. Suppose for a host with a class B IP address 167.205.9.35. Without using the subnet (will be explained later), the network address of this host is 167.205.0.0. Address is obtained by making all the host bits in the two last segments to 0. The goal is to simplify the routing information on the Internet. Router enough to see the network address (167 205) to determine the router where the datagram should be sent. The analogy is similar to the process of mail delivery, the clerk at the post office sorters just look at the destination mail address (no need to read selutuh address) to determine which path should be taken of the letter.

Broadcast Address. This address is used to send / receive information that should be known by all hosts on a network. As is known, each IP datagram header has a destination address of IP addresses of hosts that will be addressed by the datagram. With this address, so only the destination host the datagram processing, while others will host it. What if a host wants to send datagram to all hosts in its network? Inefficient if he should make as much as the amount of replication datagram destination host. Bandwidth usage will increase and the host workload increases, the contents of the same datagram-datagram. Therefore, created the concept of a broadcast address. Host simply send to the broadcast address, all hosts in the network will receive the datagram. Consequently, all hosted on the same network must have the same broadcast address and the address should not be used as an IP Address to a particular host.

So, in fact each host has two addresses to receive a datagram: the first is the IP Addressnya that is unique and the second is a broadcast address on the network where the host is located.

Broadcast address is obtained by making the host bits in the IP Address to 1. So, for the host with IP address 167.205.9.35 or 167.205.240.2, its broadcast address is 167205255255 (two last segments of the IP Address 11111111.11111111 are valuable, so it is unreadable 255 255 decimal). The type of information is usually broadcast routing information.

Multicast Address. Address classes A, B and C is the address used for communication between hosts, which uses unicast datagram-datagram. That is, the datagram / ​​packet has a destination address of a particular host. Only hosts that have the same IP address with the destination address in the datagram that will receive the datagram, while others will host it. If the datagram is addressed to all hosts on a network, then the field will contain the destination address is broadcast address from the network in question. From these two modes of delivery (unicast and broadcast), there are also modes to three. Required a special mode if a host wants to communicate with multiple hosts at once (host group), with only sends one datagram only. But unlike the broadcast mode, only the host - the host who are members of a group who will receive this datagram, while the other hosts will not be affected. Therefore, introduced the concept of multicast. In this concept, all the groups that run the application with a single multicast address. Class structure of multicast addresses can be seen in Figure below.

For the purposes of multicast, a number of IP addresses allocated as a multicast address.If the structure follows the shape 1110xxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx IP Address (224.0.0.0 decimal form to 239 255 255 255), then the IP address is a multicast address. The allocation is intended for group purposes, not for the host as in class A, B and C. Members of the group is the host - the host who wants to join the group. Members are also not limited to the network on one subnet, but can reach the whole world. Because it resembles a backbone, then the network is muticast also known as the Multicast Backbone (MBONE

Primary Election 5.Aturan network ID and host ID

Here are the ground rules in determining the network ID and host ID is used:

• Network ID can not be equal to 127

127 by default network ID is used as a loopback address ie the IP address used by a computer to appoint himself.

• Network ID and host ID must not be equal to 255

Network ID or host ID 255 will be interpreted as a broadcast address. This ID is the address that represents the entire network.

• Network ID and host ID must not be equal to 0

IP address with the host ID 0 is defined as a network address. Network address is used to designate a jaringn not a host.

• Host ID must be unique within a network.

In a network there should be no two hosts have the same host ID.

6.Subnetting

For some reason relating to the efficiency of the IP Address, resolve problems and organizational network topology, network administrators usually do subnetting. The essence of subnetting is to "move" the dividing line between the network and host part of an IP Address. Some bits from the host is allocated a bit extra on the network. Address of the network according to the standard structure is broken down into several subnetworks. This method creates a number of additional networks, but reduced the maximum number of hosts in each network.

Subnetting is also done to overcome hardware differences and the physical media used in a network. IP routers can integrate various networks with different physical media only if every network has a unique network address. In addition, with subnetting, Network Administrators can delegate a host address settings throughout the department of a large company to each department, for simplicity in managing the overall network.

A subnet is defined by implementing the masking bits (subnet mask) to the IP Address. Structure similar to the structure of the subnet mask IP address, which consists of 32 bits divided into 4 segments. The bits of the IP Address that "covered" (masking) by subnet mask bits corresponding active and will be interpreted as network bits. Bit 1 in the subnet mask means to enable masking (on), while bit 0 is off (off). In this case, let us take a single IP address with the number of class A 44.132.1.20.

With the standard rule, the IP address of this network number is 44 and the host number is 132.1.20. The network can accommodate a maximum of more than 16 million hosts are connected directly. Suppose at this address will be implemented as much as 16-bit subnet mask 255.255.0.0. (Hexa = FF.FF.00.00 or binary = 11111111.11111111.00000000.00000000). Note that in the first 16 bits of the subnet mask is worth 1, while the next 16 bits 0. Thus, the first 16 bits of an IP subnet mask address that subject will be considered as network bits. Network numbers will be changed to 44,132 and the number of hosts to be 1.20. Maximum capacity of directly connected hosts on the network to around 65 thousand hosts.

Subnet mask above is identical to the standard IP Address class B. By applying the subnet mask on a single class A network, network 256 can be made ​​new with each capacity equivalent network subnet class B. The application of more distant subnets such as 255.255.255.0 (24 bits) in class A will produce a larger number of networks (more than 65 thousand network) with the capacity of each subnet for 256 hosts. Class C network can also be subdivided into several subnets by applying the subnet mask of such higher for 25-bit (255 255 255 128), 26-bit (255 255 255 192), 27-bit (255 255 255 224) and so on.

Subnetting made ​​during interface configuration. Application of the subnet mask in the IP Address will define two new pieces address, ie Network Address and Broadcast Address. Network address is defined by setting all the host bits worth 0, while the broadcast address by setting the host bits worth 1. As has been dijelasakan in the previous section, the network address is the network that is useful in routing information. A host that does not need to know the address all hosts in the network to another. The information needed was the address of the network will be contacted as well as the gateway to reach the network. Illustration of subnetting, network address and broadcast address can be seen in Table below.

IP Address	Network Address Standard	Subnet Mask	Interpretasi	Broadcast Address
44.132.1.20	44.0.0.0	255.255.0.0 (16 bit)	Host 1.20 pada               subnet  44.132.0.0	44.132.255.255
81.150.2.3	81.0.0.0	255.255.255.0 (24 bit)	Host 3 pada  subnet 81.50.2.0	81.50.2.255
167.205.2.100	167.205.0.0	255.255.255.128 (25 bit)	Host 100 pada Subnet 167.205.2.0	167.205.2.127
167.205.2. 130	167.205.0.0	255.255.255.192 (26 bit)	Host 130 pada  subnet 167.205.2.128	167.205.2.191

Subnetting is only valid on the local network. For the network beyond the local network, network numbers are identified according to standard fixed network number-class IP Address.