Linux networking - ip address and subnet mask

Networking is essential when talking Linux into subject. As you already know, Linux derived from Unix which serve network as servers. So Linux user must have a basic knowledge about networking, especially the IP protocols and ethernet.

IP protocol is one of the protocols that make a networking possible. What is a protocol? In a computer networking jargon, a protocol is a rules that govern communication between two systems. Like a language in human world which allows human to communicate with each other. So, ip protocol is a standard communication rules in computer networking. In order to understand each other, all operating system, Linux, windows, Unix, Mac OS must follow one rules or protocol. That's the brief desciption of ip protocol. Now you know that Internet uses the ip protocol :-)

When talking about ip protocol, you should know the next subject which is ip address. Ip address is a unique address assigned to one network computer. This is important because a network computer must know which computer it is communicating with such as in client talking to a server situation. Ip address is divided into three classes which are class A, class B and class C.

Next is subnet mask. Every time we assign an ip address to a network computer, we must also assign a subnet mask. Ip address comes with different subnet mask depending on it's class. In each ip classes, the subnet mask defines network segment of that system. It says how much of the address is used for the network is defined by the subnet mask.

Ip address classes and subnet mask:

  • Class A The decimal value of the first octet must be between 1 and 126.
    In a Class A address, the first octet is the network address and the last three
    octets are the node address. Therefore, the default subnet mask is 255.0.0.0.
  • Class B The decimal value of the first octet must be between 128 and 191.
    In a Class B address, the first two octets are the network address and the
    last two octets are the node address. Therefore, the default subnet mask is
    255.255.0.0.
  • Class C The decimal value of the first octet must be between 192 and
    223. In a Class C address, the first three octets are the network address while
    the last octet is the node address. Therefore, the default subnet mask is
    255.255.255.0.

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