` Easy IPv4 Subnetting and Mask Calculation Method - Interlir networks marketplace
bgunderlay bgunderlay bgunderlay

Easy IPv4 Subnetting and Mask Calculation Method

In the realm of network engineering and administration, understanding how to efficiently subdivide IP networks into smaller, manageable segments—known as subnetting—is fundamental. With the advent of IPv4’s limited address space, subnetting has become an essential skill to optimize the use of IP addresses.

Understanding the Basics of IPv4 Subnetting

IPv4 addresses consist of 32 bits, typically represented in decimal format as four octets separated by dots (e.g., 192.168.1.1). Subnetting involves dividing a network into smaller networks (subnets) to improve network management and security. This division is achieved through the subnet mask, which determines how many bits are used for the network portion and how many for the host portion of an address.

The Simple 6-Step Subnetting Method

To simplify subnetting, follow this straightforward six-step method, which can be applied to any IPv4 address:

Step 1: Find the Subnet Number

  1. Subtract the prefix number from /32: For example, for a /29 prefix, it’s 32 – 29 = 3.
  2. Calculate the Subnet Mask: Convert the remaining bits to binary and sum them up to find the subnet mask.

Step 2: Determine the Subnet Size

  1. Calculate the subnet size: Use the formula 2^n (where n is the number of host bits) to find how many addresses are in each subnet.

Step 3: Identify the Broadcast Address

  1. Subtract 1 from the subnet size: This gives you the broadcast address for the subnet.

Step 4: Locate the IP Address Subnet

  1. Identify which subnet block the IP address falls into: This determines the range of valid host addresses.

Step 5: Calculate Valid Hosts

  1. Determine the number of valid hosts per subnet: Subtract 2 from the subnet size (for the network and broadcast addresses).

Example

Following this method, the subnetting details for the IP address 10.20.4.13 with a /29 prefix are as follows:

  1. Subnet Address: 10.20.4.8/29
  2. First Valid Host Address: 10.20.4.9
  3. Last Valid Host Address: 10.20.4.14
  4. Broadcast Address: 10.20.4.15
  5. Subnet Mask: 255.255.255.248

Variable Length Subnet Mask (VLSM) Table

A Variable Length Subnet Mask (VLSM) allows for the subnet masks of variable lengths to be used within the same network, providing more flexibility and efficiency in IP address allocation. Here’s a brief overview:

Prefix sizeNetwork maskUsable hosts per subnet
/1128.0.0.02,147,483,646
/2192.0.0.01,073,741,822
/3224.0.0.0536,870,910
/4240.0.0.0268,435,454
/5248.0.0.0134,217,726
/6252.0.0.067,108,862
/7254.0.0.033,554,430
Class A
/8255.0.0.016,777,214
/9255.128.0.08,388,606
/10255.192.0.04,194,302
/11255.224.0.02,097,150
/12255.240.0.01,048,574
/13255.248.0.0524,286
/14255.252.0.0262,142
/15255.254.0.0131,070
Class B
/16255.255.0.065,534
/17255.255.128.032,766
/18255.255.192.016,382
/19255.255.224.08,190
/20255.255.240.04,094
/21255.255.248.02,046
/22255.255.252.01,022
/23255.255.254.0510
Class C
/24255.255.255.0254
/25255.255.255.128126
/26255.255.255.19262
/27255.255.255.22430
/28255.255.255.24014
/29255.255.255.2486
/30255.255.255.2522
/31255.255.255.2540 (special use)
/32255.255.255.2550 (single host)

Conclusion

Subnetting is a critical skill in network design and management, enabling the efficient use of IP addresses and enhanced network security. By mastering the easy six-step method outlined above, network administrators and engineers can simplify the subnetting process. Remember, practice is key to becoming proficient in subnetting and mask calculations. With these tools and methods, navigating the complexities of IPv4 networks becomes a more manageable and straightforward task.

Evgeny Sevastyanov

Client Support Teamleader

    Ready to get started?

    Articles
    Renting/leasing/purchasing
    Renting/leasing/purchasing

    Having a clear understanding of the different types and purposes of IP addresses

    More
    How to do IP address abuse management in 2024
    How to do IP address abuse management in 2024

    the rights to manage blocks of IP addresses are constantly faced with a dilemma.

    More
    European IPv4 addresses marketplace
    European IPv4 addresses marketplace

    In 2011, RIPE announced the depletion of IPv4 addresses. IPv4 addresses continue

    More
    Digital future and IPv4 address
    Digital future and IPv4 address

    addresses are trite. The allocation from the Primary IPv4 Registry, begun by John

    More
    What is an IPv4 address?
    What is an IPv4 address?

    unique identifier that points to each device on the internet and allows them to communicate

    More
    The great IP space redistribution
    The great IP space redistribution

    One of the possible ways to support the development of the IT sector is the effective

    More
    How to Monetize IP Network
    How to Monetize IP Network

    Even if you don’t plan to sell your IPv4 network, there are still ways to make

    More
    INTERLIR: IPv4 Address Broker and Networks Marketplace
    INTERLIR: IPv4 Address Broker and Networks Marketplace

    InterLIR GmbH is a marketplace solution that aims to solve network availability problems

    More
    Managing IPv4 Scarcity Through IP Lease
    Managing IPv4 Scarcity Through IP Lease

    l IPv4, where is possible only 4,3 billion combination of the numbers.

    More
    Sell IPv4 Addresses
    Sell IPv4 Addresses

    The increasing demand for IP blocks has driven up prices and transformed overused

    More