Answers: Summary Route Practice Set 2

This post lists the answers to summary route practice set 2. If you’ve not tried these problems yet, go back, check it out, and come up with the best summary route. Then come back here and check your answers.

The answer to each of the three problems uses two tables. The first table lists the original masks and subnet IDs of the routes that need to be summarized as one route, along with the calculated subnet broadcast addresses. These tables also show the low and high end of the address range in total, with bold text for the lowest subnet ID (the low end of the range) and bold text for the highest subnet broadcast address (the high end of the range). The best summary route will be the first subnet/mask combination found that includes both the low and high-end numbers.

The second table for each answer lists the calculation of potential correct answers, with the correct answer listed in bold. The table shows each successive calculation of a new subnet ID, using a new /P mask, and its broadcast address. (See this post for details about the process.) The table shows the calculations with each /P being 1 smaller than the previous, until it lists the correct answer.

Note that the second table for each problem includes a final summary route with a mask (/P) one shorter than the correct best summary route. This last route also includes the entire range of addresses, and could be used as a summary, but is not considered the best summary route, because it includes an unnecessarily broad range of addresses.

Problem 1: Answers

The following table lists the original masks and subnets, the calculated broadcast addresses for each, and notes the lowest and highest numbers in the range in bold.

Problem 1, Original Subnets and Broadcast Addresses

If you are using the literal process shown in aforementioned post about how to find summary routes, the next table shows the results of working repeatedly through step 4. If not… the table shows a calculation, using progressively smaller masks, calculating a new subnet ID and matching broadcast address, using the smallest original subnet ID.

Note that the bold route in the table is the best summary route.

Problem 1, Calculation Using 10.99.192.0, New /P

Problem 2: Answers

The following table lists the original masks and subnets, the calculated broadcast addresses for each, and notes the lowest and highest numbers in the range in bold.

Problem 2, Original Subnets and Broadcast Addresses

If you are using the literal process shown in aforementioned post about how to find summary routes, the next table shows the results of working repeatedly through step 4. If not… the table shows a calculation, using progressively smaller masks, calculating a new subnet ID and matching broadcast address, using the smallest original subnet ID.

Note that the bold route in the table is the best summary route.

Problem 2, Calculation Using 172.16.140.0, New /P

Problem 3: Answers

The following table lists the original masks and subnets, the calculated broadcast addresses for each, and notes the lowest and highest numbers in the range in bold.

Problem 3, Original Subnets and Broadcast Addresses

If you are using the literal process shown in aforementioned post about how to find summary routes, the next table shows the results of working repeatedly through step 4. If not… the table shows a calculation, using progressively smaller masks, calculating a new subnet ID and matching broadcast address, using the smallest original subnet ID.

Note that the bold route in the table is the best summary route.

Problem 3, Calculation Using 192.168.1.200, New /P