We will walk through the process of subnetting a network and performing route summarization using an example.

Subnetting Example

Let’s consider the following four subnets:

• 192.168.0.0/22
• 192.168.4.0/22
• 192.168.8.0/22
• 192.168.12.0/22

Binary Representation

To better understand these subnets, let’s convert the IP addresses to their binary form:

• 192.168.0.0:    11000000.10101000.00000000.00000000
• 192.168.4.0:    11000000.10101000.00000100.00000000
• 192.168.8.0:    11000000.10101000.00001000.00000000
• 192.168.12.0:  11000000.10101000.00001100.00000000

Common Bits

With a subnet mask of /22, we need to consider the first 22 bits of each IP address. Here are the first 22 bits for each:

• 192.168.0.0:  11000000.10101000.000000
• 192.168.4.0:  11000000.10101000.000001
• 192.168.8.0:  11000000.10101000.000010
• 192.168.12.0: 11000000.10101000.000011

Route Summarization

Route summarization involves aggregating these subnets into a single, larger subnet. In our example, the first 22 bits (11000000.10101000.0000) are common across all four subnets. Therefore, we can summarize these subnets with a single route:

• Aggregated Route: 192.168.0.0/22

Distinguishing Digits

The last two digits of each IP address in the binary representation distinguish each subnet:

• 192.168.0.0:    00
• 192.168.4.0:    01
• 192.168.8.0:    10
• 192.168.12.0:  11

These last two digits indicate the specific subnets within the aggregated route.

Conclusion

Understanding the principles of subnetting and route summarization is crucial for efficient network management. By aggregating routes, we can reduce the size of routing tables and simplify network administration. Using the example above, we’ve demonstrated how to identify common bits, summarize routes, and distinguish individual subnets.