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Computer Networks Subnetting and Supernetting

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Subnetting and Supernetting Notes

Information Needed to Solve the Problem

To solve problems involving subnetting and determining the range of IP addresses, here’s the essential information you need:

  1. IP Address:

    • This is the starting point. In this case, it is given as 205.16.37.32 or 205.16.37.39, depending on the example being worked on.

  2. Subnet Mask:

    • This tells us how many bits are allocated to the network portion versus the host portion of the IP address.
    • For example, a subnet mask of 28 means 28 bits are allocated for the network, and 4 bits are available for hosts.

  3. Number of IP Addresses:

    • The number of available IP addresses in a subnet is determined by the number of bits used for the host portion.

    • The formula for calculating the number of IP addresses is:

    • In a 28 subnet, 4 bits are available for hosts, which gives us IP addresses.

  4. Binary Conversion:

    • Understanding how to convert IP addresses into their binary form allows you to easily calculate the first and last address in a block.

    • Example: The IP address 205.16.37.32 is converted into binary, which gives:

      11001101.00010000.00100101.00100000

  5. First and Last Address Calculation:

    • To find the first address, set the host bits to all zeros (0).
    • To find the last address, set the host bits to all ones (1).

Key Concepts:

  1. Subnetting:

    • Increases the number of 1s in the subnet mask.
    • Helps divide a network into smaller sub-networks (subnets).

  2. Supernetting:

    • Increases the number of 1s in the mask.
    • Combines multiple networks into a larger one.

Problem 1:

Description:

A block of 16 addresses is granted to a small organization. The first address is given as 205.16.37.32, and the task is to find the binary representation of the first and last addresses in this block.

Given:

  • First address: 205.16.37.32 (in binary: 11001101.00010000.00100101.00100000)
  • Last address: 205.16.37.47

Solution:

  1. Addresses are contiguous.
  2. The number of addresses is a power of 2: 16 = 2^4.
  3. The first address is divisible by 16 (starting from 205.16.37.32).

Problem 2:

Description:

A block of addresses is granted to a small organization. One of the addresses given is 205.16.37.39/28. The task is to find the first address in this block.

Solution:

  • Binary representation of the given address: 11001101 00010000 00100101 00100111
  • Using the subnet mask /28, we know there are 4 position zeros for the host portion.

First Address:

  • The first address in binary: 11001101 00010000 00100101 00100000
  • Therefore, the first address is 205.16.37.32.

Last Address:

  • Set the last 4 bits of the host portion to 1s for the last address.
  • The last address is: 11001101 00010000 00100101 00101111
  • Therefore, the last address is 205.16.37.47.

Additional Method for Finding Addresses:

Given an IP address: 205.16.37.39/28, we can calculate the number of addresses in the block using the formula:

[ \text{Number of addresses} = 2^{32 - 28} = 2^4 = 16 \text{ addresses} ]

The first address is 205.16.37.32, and the last address is 205.16.37.47.

Binary Representation of IP Addresses:

For the address 205.16.37.32:

  • 205 in binary: 11001101
  • 16 in binary: 00010000
  • 37 in binary: 00100101
  • 32 in binary: 00100000

The binary representation: 11001101.00010000.00100101.00100000

Similarly, for 205.16.37.47:

  • 205 in binary: 11001101
  • 16 in binary: 00010000
  • 37 in binary: 00100101
  • 47 in binary: 00101111

The binary representation: 11001101.00010000.00100101.00101111

Formula Recap:

  • First address: Convert the IP address to binary, and set the host bits to 0.
  • Last address: Convert the IP address to binary, and set the host bits to 1.

References

Information
  • date: 2024.10.07
  • time: 07:39

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