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What is the usable number of host IP addresses on a network that has a /26 mask?

What is the usable number of host IP addresses on a network that has a /26 mask?

  • 256
  • 254
  • 64
  • 62
  • 32
  • 16

The correct answer is 62.

Detailed Explanation:

In networking, the concept of IP addressing is fundamental for identifying devices on a network. The Internet Protocol (IP) is responsible for addressing and routing packets of data so they can travel across networks and arrive at the correct destination. One of the core elements of IP addressing is the subnet mask, which determines the size of the network and the number of available IP addresses within that network.

Understanding the /26 Subnet Mask

A subnet mask divides an IP address into two parts: the network portion and the host portion. The subnet mask helps identify which part of the IP address refers to the network and which part refers to the hosts (i.e., devices) within that network. In IPv4, an IP address is 32 bits long, and the subnet mask indicates how many of those bits are used for the network portion.

When we say a network has a /26 mask, we are using CIDR (Classless Inter-Domain Routing) notation, where “/26” means that the first 26 bits of the IP address are used for the network portion, and the remaining 6 bits are available for host addresses.

Binary Representation

To understand how the /26 subnet works, it’s important to look at the binary representation:

  • IPv4 Address: 32 bits
  • /26 Subnet Mask: 11111111.11111111.11111111.11000000

Breaking this down:

  • The first 26 bits are set to 1 (indicating the network portion).
  • The remaining 6 bits are set to 0 (indicating the host portion).

This means that the subnet mask in decimal is 255.255.255.192.

Calculating the Number of Hosts

The number of usable host IP addresses in a subnet is determined by the number of bits available for hosts. In the case of a /26 subnet, 6 bits are available for host addresses.

To calculate the number of hosts:

  1. Determine the total number of IP addresses:
    • Since 6 bits are available for hosts, the total number of possible IP addresses is 2^6 = 64.
  2. Account for network and broadcast addresses:
    • In any subnet, two IP addresses are reserved and cannot be assigned to hosts. These are:
      • Network Address: The first IP address in the subnet, which identifies the network itself.
      • Broadcast Address: The last IP address in the subnet, used to communicate with all devices on the network.
    • Therefore, the number of usable IP addresses is 64 – 2 = 62.

Thus, in a /26 subnet, there are 62 usable IP addresses that can be assigned to devices.

Practical Implications of a /26 Subnet

A /26 subnet provides a moderate number of IP addresses, making it suitable for small to medium-sized networks, such as a small office or department within a larger organization. With 62 usable IP addresses, you can connect a decent number of devices, including computers, printers, servers, and other networked equipment.

For example, consider a company that has several departments, each needing its own subnet to isolate traffic and manage IP address allocation more efficiently. A /26 subnet would be appropriate for a department with up to 62 devices. This setup helps to minimize broadcast traffic within the subnet, ensuring that network performance remains optimal even as the number of connected devices grows.

Example Scenario

Let’s consider a practical scenario where a /26 subnet might be used:

  • Company Network: A company with a central office and several departments.
  • Department A: The IT department has its own subnet with a /26 mask.
  • Network Configuration:
    • Network address: 192.168.1.0/26
    • Subnet mask: 255.255.255.192
    • Usable IP range: 192.168.1.1 to 192.168.1.62
    • Broadcast address: 192.168.1.63

In this scenario, the IT department can assign IP addresses to up to 62 devices. The network administrator would allocate these IP addresses based on the department’s requirements, ensuring that every device can communicate within the network and access shared resources like servers or printers.

Scalability Considerations

While a /26 subnet is sufficient for many small networks, scalability is an important consideration. If the number of devices in the network is expected to grow significantly, the organization might need to consider a different subnet mask that offers more IP addresses, such as a /25 subnet (with 126 usable IP addresses) or even a /24 subnet (with 254 usable IP addresses).

However, using a smaller subnet like /26 can also be beneficial in terms of security and network management. By limiting the number of devices in a subnet, it’s easier to control access, monitor traffic, and isolate potential security threats. This is particularly important in environments where different departments or teams require varying levels of access and security.

Conclusion

In summary, a network with a /26 subnet mask has 62 usable IP addresses. This configuration is suitable for small to medium-sized networks, providing enough IP addresses for a variety of devices while maintaining manageable levels of broadcast traffic. Understanding how subnet masks work and how to calculate the number of usable IP addresses is crucial for network design and management, ensuring that networks are both efficient and scalable.