How to on IPv4?



  • IPv4 uses binary numbering, which means 0 or 1, The 0 and 1 are called bits

    Servers & Network devices are given numbers to uniquely identify them in a network, this is called addressing.

    A server or laptop is given a network address which consists of number that is 32 bits long.
    The 32 bits is divided into 4 groups of 8 binary numbers called octets.

    For example:

    The full binary address
    00001010000000010011001000000010

    The full binary address broken up into 4 groups of 8 binary numbers, there is a dot after every 8 bits
    00001010.00000001.00110010.00000010

    As these numbers are not practical for people to use, they are converted to the decimal equivalent. The computer will however carry on using the 32 bit binary numbers.

    Here's an example of a conversion from binary to decimal
    00001010.00000001.00110010.00000010 = 10.1.50.2

    To explain you how that gets converted

    The decimal numbering works of the number 10, binary works of the number 2.

    For decimal numbers 0 - 9 the total amount of numbers is 10
    For binary numbers 0 - 1 the total amount of numbers is 2

    Let's work out the numbers in the position notation, to provide and example for a decimal number 2468

    Read out that says two thousand, four hundred, and sixty eight.

    Description Thousands Hundreds Tens Ones
    Positional Value 1000 100 10 1
    Decimal number 2 4 6 8
    Calculate 2 x 1000 4 x 100 6 x 10 8 x 1
    Add up 2000 400 60 8

    And that makes 2468

    Now let's do a binary number, the base number is 2, position starts from right to left, begins with zero

    Description Position seven Position six Position five Position four Position three Position two Position one Position zero
    Base Number 2 2 2 2 2 2 2 2
    Position of number 7 6 5 4 3 2 1 0
    Calculate 2^7 2^6 2^5 2^4 2^3 2^2 2^1 2^0
    Add up 128 64 32 16 8 4 2 1

    Keep that table in mind and recall our binary number
    00001010.00000001.00110010.00000010 = 10.1.50.2

    The first number in our IP address is 10 which in binary format is 00001010, let's see how.

    Description Position seven Position six Position five Position four Position three Position two Position one Position zero
    Positional value 128 64 32 16 8 4 2 1
    Our binary number 0 0 0 0 1 0 1 0
    Calculate 0 x 128 0 x 64 0 x 32 0 x 16 1 x 8 0 x 4 1 x 2 0 x 0
    Add up 0 0 0 0 8 0 2 0

    The result is 8 + 2 = 10
    We have our first number converted, if you do the same for the other numbers you get the IP address 10.1.50.2


    The IP address structure

    The 32 bit binary number IP address is split into two, a host part and a network part.

    The network part and the host part is determined by something called a Subnet Mask "1's" are the network part of the address and "0's" are the host/device part.

    The process of determining what the network address is a comparison of the binary numbers of the IPv4 IP and the binary number of the subnet mask. The process uses digital logic, called ANDing

    1 AND 1 = 1
    0 AND 1 = 0
    0 AND 0 = 0
    1 AND 0 = 0

    Description Octet 1 Octet 2 Octet 3 Octet 4
    IPv4 IP 10 1 50 2
    IPv4 Binary 00001010 00000001 00110010 00000010
    Subnet Mask 255 255 255 0
    Subnet Mask Binary 11111111 11111111 11111111 00000000
    ANDing 00001010 00000001 00110000 00000000
    Resulting Network Address 10 1 50 0

    The resulting network address is from converting ANDing to the decimal equivalent using the binary positional values we discussed earlier.

    Specifying decimal network address and host address with subnet mask is a bit long winded.

    To make this easier a short version is just to count the number of "1's" in the subnet mask and put that in a slash "/" notation.

    A commonly used one is

    255.255.255.0 11111111.11111111.11111111.00000000 /24

    Another one is:

    255.255.255.252 11111111.11111111.11111111.11111100 /30

    A network identity has the following address associated with it.
    Network Address
    Host Addresses
    First Host Address
    Last Host Address
    Broadcast Address

    Staying with our example IP: 10.1.50.2

    Network Address = 10.1.50.0/24
    Host Addresses, Range from = 10.1.50.1/24 - 10.1.50.254/24
    Broadcast Address = 10.1.50.255/24


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