What Wild Card Mask Will Match Networks 172.16.0.0 Through 172.19.0.0

What Wildcard Mask Will Match Networks 172.16.0.0 Through 172.19.0.0? A Deep Dive into Subnetting and IP Addressing

Understanding subnet masks and wildcard masks is crucial for effective network administration. This article delves into the specifics of identifying the wildcard mask that accurately matches the IP address range of 172.16.0.0 through 172.19.0.0. We'll explore the underlying principles of IP addressing, subnetting, and wildcard masks to provide a comprehensive understanding.

Understanding IP Addresses and Subnet Masks

Every device connected to a network needs a unique IP address for communication. An IPv4 address is a 32-bit number, typically represented in dotted decimal notation (e.g., 192.168.1.10). This address is divided into two parts: the network address and the host address. The subnet mask determines the boundary between these two parts.

A subnet mask is a 32-bit number that identifies the network portion of an IP address. It uses binary 1s to represent the network bits and binary 0s to represent the host bits. For example, a subnet mask of 255.255.255.0 (or /24 in CIDR notation) means the first three octets (bytes) identify the network, and the last octet identifies the host within that network.

Classful vs. Classless Addressing

Historically, IP addressing was divided into classes (A, B, C), each with a predetermined subnet mask. However, this system proved inefficient, leading to the adoption of Classless Inter-Domain Routing (CIDR). CIDR uses slash notation (/n), where 'n' represents the number of bits used for the network address. This allows for more flexible and efficient subnetting.

Subnetting and Network Segmentation

Subnetting divides a larger network into smaller, more manageable subnetworks. This improves network performance, security, and scalability. By using different subnet masks, you can create multiple subnetworks within a single larger network address space. This is essential for large organizations and complex networks.

Wildcard Masks: The Inverse of Subnet Masks

A wildcard mask is the inverse of a subnet mask. It's used in conjunction with IP addresses to define a range of addresses. While a subnet mask identifies the network portion, a wildcard mask identifies the variable portion of the IP address. A wildcard mask uses 0s where the subnet mask has 1s, and vice-versa. It essentially highlights the bits that can vary within a network range.

How Wildcard Masks Work:

A wildcard mask works by performing a bitwise AND operation between the wildcard mask and the IP address. Any bit that's a '1' in the wildcard mask will be considered variable. This allows you to match a range of addresses rather than a single address.

Determining the Wildcard Mask for 172.16.0.0 - 172.19.0.0

To determine the wildcard mask that encompasses the IP range 172.16.0.0 through 172.19.0.0, we need to first determine the appropriate subnet mask.

Let's analyze the IP range:

• Starting IP: 172.16.0.0
• Ending IP: 172.19.0.0

Notice that the first two octets (172.16 and 172.19) are changing. The third and fourth octets remain constant at 0.0. This indicates that the subnet mask must allow variation in the second octet.

The difference between 172.19 and 172.16 is 3 (19 - 16 = 3). To represent 3 in binary, we need two bits (11). We have four possibilities which are 172.16, 172.17, 172.18, and 172.19. Since we have 2^2 we know it takes 2 bits to represent this range.

Therefore, to accommodate this range, we need a subnet mask that allows for at least 3 more values that is represented by 2 bits, or a total of 10 bits for the network address. That is 2^10 = 1024. Since the first octet (172) is constant, we must ensure the mask only changes at the second octet.

To find the number of bits needed for the network address, we need to find the number of networks that we need to cover:

We have a range of 4 networks (172.16.0.0, 172.17.0.0, 172.18.0.0, 172.19.0.0). This can be expressed as 2^2 which is 4. This means that only two extra bits are needed in the network address. This will mean we have 22 bits for network and 10 bits for host address, as shown in the CIDR notation /22.

Calculating the Subnet Mask:

A /22 subnet mask is calculated as follows:

• 22 bits for the network portion
• 10 bits for the host portion (32 total bits - 22 network bits = 10 host bits)

In dotted decimal notation, this translates to 255.255.252.0.

Calculating the Wildcard Mask:

The wildcard mask is the inverse of the subnet mask. Therefore, we invert each octet:

• 255 becomes 0
• 252 becomes 3

This gives us a wildcard mask of 0.0.3.255.

Verifying the Wildcard Mask

Let's test this wildcard mask with some IP addresses within the specified range:

• 172.16.0.0: 0.0.3.255 AND 172.16.0.0 = 0.0.0.0 (This is a match)
• 172.19.0.0: 0.0.3.255 AND 172.19.0.0 = 0.0.0.0 (This is also a match)
• 172.17.0.0: 0.0.3.255 AND 172.17.0.0 = 0.0.0.0 (This is a match)
• 172.18.0.0: 0.0.3.255 AND 172.18.0.0 = 0.0.0.0 (This is a match)
• 172.15.0.0: 0.0.3.255 AND 172.15.0.0 = Will give a result that is not zero meaning it is not part of the network range.

As you can see, the wildcard mask of 0.0.3.255 accurately identifies all IP addresses within the 172.16.0.0 to 172.19.0.0 range.

Practical Applications of Wildcard Masks

Wildcard masks are particularly useful in network security and filtering. They are used in Access Control Lists (ACLs) and firewall rules to define which IP addresses should be allowed or denied access to a network. They are also valuable for network monitoring and troubleshooting, allowing network administrators to easily identify traffic patterns and potential problems.

Conclusion

Determining the appropriate wildcard mask for a given IP address range requires a thorough understanding of subnetting and IP addressing. By carefully analyzing the IP range and applying the principles of subnet mask calculation and inversion, we can effectively identify the wildcard mask that accurately reflects the desired range. In this case, the wildcard mask 0.0.3.255 correctly matches the networks 172.16.0.0 through 172.19.0.0. Understanding this concept is crucial for efficient network management and security. Remember to always double-check your calculations to avoid misconfigurations and potential network disruptions. Effective use of wildcard masks enhances network control and facilitates the management of complex network infrastructures.