What You Should Know about MAC and IP Addresses

August 1, 2016 | Views: 12617

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MAC and IP addresses are two important topics that a person involved in the Computer Networking  and Computer Security fields should know about.

These topics are discussed below.

 

1.MAC Address

A MAC address is a address that is burned into the hardware itself during the manufacturing period and it cannot be changed. MAC addresses are 48 bits. Ex: 01:23:45:67:89:ab.

Here, each byte is represented by its hexadecimal value. The first 3 bytes (in this case “01:23:45”) are known as Organizational Unique Identifier, which gives the identity of the organization that the MAC address/device belongs to. For Ex: the OUI “01:23:45” may belong to a company called X. The IEEE assigns OUI to vendors. The remaining 3 bytes will uniquely identify the device itself. No two devices will have the same MAC address. MAC addresses are also known as physical addresses/Ethernet Hardware Address (EHA)/Burned In Address (BIA).

 

2. IP Address

While MAC addresses are physical, IP addresses are logical. Devices on a different network can, and most likely will, have the same IP address. IP address are of 32 bits. Ex 192.168.5.1. There are different classes of IP’s.

Class A = 1 – 126

Class B = 128 – 191  # 127 is used as loopback address

Class C = 192 – 223

Class D = 224 – 239

Class E = 240 – 254

The IP address contains network and host bits which are separated using subnet masks. For Ex: an IP address 192.168.5.1 has subnet mask of 255.255.255.0. For basic understanding, the octet whose value is 255 can be considered as network bits. Here, 192.168.5, is the network bit, which identifies a network where as .1 is the host bit that identifies a host.

 

A Technique To Remember

Consider a school, which has many classrooms. Each classroom has many students with their own Roll numbers. OH! And, also none of the students have same name.

Each class can have Roll numbers which another class may also have.

Consider the school as internet, each classroom as a network, the roll number as an IP address and the individual student’s name as a MAC address.

Note: A MAC address is used only on a LAN and operates on layer 2 of the of  the OSI model. IP address is used for routing and operates on layer 3 of OSI model.

 

More information:

OSI: https://en.wikipedia.org/wiki/OSI_model

IP: https://tools.ietf.org/html/rfc791

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30 Comments
  1. I don’t agree that the MAC address cannot be changed. It’s fair to say that the MAC is reset to a factory-assigned value every time that the host is powered on, but not that it’s immutable.

    There are various methods for changing a NIC’s MAC. On Linux, as root:

    # ifconfig eth0 down
    # ifconfig eth0 hw ether 00:80:48:BA:d1:30
    # ifconfig eth0 up

    And on Windows, googling ‘Windows change MAC address’ will return many articles on how to do it.

  2. what actually loop address means??And What IP class A does?Is it a network bits?

    • Loop address means your own computer IP address, Every PC in the world has same loop back address i.e. 127.0.0.1 and it usually used to check if there is a network related problem in you computer. Class A IP is just a address range of IP, It is not network bits. Class A IP has range from 1.0.0.1 to 126.255.255.254, it’s default subnet mask is 255.0.0.0, meaning only the firs part are network bits i.e 1.0.0.2,1.0.0.3 the 1 in these IP are network bits and rest are host bits

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