What Wild Card Mask Will Match Networks 172.16.0.0 Through 172.19.0.0

When it comes to networking, understanding IP addressing and subnetting is crucial. One important aspect of subnetting is determining the appropriate wild card mask to match a specific range of IP addresses. In this article, we will explore the wild card mask that matches networks ranging from 172.16.0.0 to 172.19.0.0. We will delve into the concept of wild card masks, explain how they work, and provide examples to illustrate their application.

Understanding Wild Card Masks

A wild card mask, also known as an inverse mask, is used in conjunction with an IP address to define a range of addresses. It is the inverse of a subnet mask, where each bit represents whether a corresponding bit in the IP address should be considered or ignored. A wild card mask allows for more flexibility in defining address ranges compared to a subnet mask.

Wild card masks are commonly used in access control lists (ACLs) to permit or deny traffic based on specific IP address ranges. By specifying a wild card mask, network administrators can define a range of IP addresses that should be matched or excluded from a particular rule or policy.

Determining the Wild Card Mask

To determine the wild card mask that matches networks ranging from 172.16.0.0 to 172.19.0.0, we need to examine the binary representation of the IP addresses involved.

The IP address range 172.16.0.0 to 172.19.0.0 can be represented in binary as follows:

• 172.16.0.0: 10101100.00010000.00000000.00000000
• 172.19.0.0: 10101100.00010011.00000000.00000000

By comparing the binary representation of the two IP addresses, we can identify the bits that are different. In this case, the third octet (00010000 and 00010011) is the only octet that differs between the two addresses.

To determine the wild card mask, we need to find the binary representation of the bits that differ. In this case, the third octet differs by two bits: the fourth and fifth bits (00010000 and 00010011).

Converting these differing bits to a wild card mask, we get:

• Fourth bit: 1 -> 0
• Fifth bit: 0 -> 1

Combining these bits, the wild card mask for the given IP address range is 0.0.3.255.

Applying the Wild Card Mask

Now that we have determined the wild card mask (0.0.3.255) for the IP address range 172.16.0.0 to 172.19.0.0, let’s see how it can be applied in practice.

Suppose we have an ACL rule that needs to match all IP addresses within this range. We can use the wild card mask to define the range in the ACL configuration. For example:

access-list 1 permit ip any 172.16.0.0 0.0.3.255

In this configuration, the wild card mask (0.0.3.255) is applied to the IP address 172.16.0.0, indicating that any IP address within the range 172.16.0.0 to 172.19.0.0 should be permitted by the ACL rule.

Examples and Case Studies

Let’s explore a few examples and case studies to further illustrate the application of wild card masks in matching IP address ranges.

Example 1:

Suppose we have an ACL rule that needs to match all IP addresses within the range 172.16.0.0 to 172.16.255.255. To determine the wild card mask, we compare the binary representation of the two IP addresses:

• 172.16.0.0: 10101100.00010000.00000000.00000000
• 172.16.255.255: 10101100.00010000.11111111.11111111

The differing bits are in the third and fourth octets (00000000 and 11111111). Converting these differing bits to a wild card mask, we get 0.0.255.255.

The ACL configuration to match this range would be:

access-list 1 permit ip any 172.16.0.0 0.0.255.255

Example 2:

Suppose we have an ACL rule that needs to match all IP addresses within the range 172.17.0.0 to 172.17.255.255. Following the same process as before, we compare the binary representation of the two IP addresses:

• 172.17.0.0: 10101100.00010001.00000000.00000000
• 172.17.255.255: 10101100.00010001.11111111.11111111

The differing bits are in the third and fourth octets (00000000 and 11111111). The wild card mask for this range is 0.0.255.255.

The ACL configuration to match this range would be:

access-list 1 permit ip any 172.17.0.0 0.0.255.255

Frequently Asked Questions (FAQ)

Q1: What is the purpose of a wild card mask?

A1: A wild card mask is used to define a range of IP addresses in access control lists (ACLs) or other network configurations. It allows network administrators to specify which IP addresses should be matched or excluded based on their binary representation.

Q2: How does a wild card mask differ from a subnet mask?

A2: A wild card mask is the inverse of a subnet mask. While a subnet mask determines the network and host portions of an IP address, a wild card mask determines which bits should be considered or ignored when matching IP addresses.

Q3: Can a wild card mask be used with IPv6 addresses?

A3: No, wild card masks are specific to IPv4 addresses. IPv6 uses a different