Exam Essentials

Identify the advantages of subnetting. Benefits of subnetting a physical network include reduced network traffic, optimized network performance, simplified management, and facilitated spanning of large geographical distances.

Describe the effect of the ip subnet-zero command. This command allows you to use the first and last subnet in your network design.

Identify the steps to subnet a classful network. Understand how IP addressing and subnetting work. First, determine your block

size by using the 256-subnet mask math. Then count your subnets and determine the broadcast address of each subnet—it is always the number right before the next subnet. Your valid hosts are the numbers between the subnet address and the broadcast address.

Determine possible block sizes. This is an impor tant part of understanding IP addressing and subnetting. The valid block sizes are always 2, 4, 8, 16, 32, 64, 128, etc. You can determine your block size by using the 256-subnet mask math.

Describe the role of a subnet mask in IP addressing. A subnet mask is a 32-bit value that allows the recipient of IP packets to distinguish the network ID portion of the IP address from the host ID portion of the IP address.

Understand and apply the 2 – 2 formula. Use this formula to determine the proper subnet mask for a particular size network given the application of that subnet mask to a particular classful network.

Explain the impact of Classless Inter-Domain Routing (CIDR). CIDR allows the creation of networks of a size other than those allowed with the classful subnetting by allowing more than the three classful subnet masks.

Written Labs

In this section, you’ll complete the following labs to make sure you’ve got the information and concepts contained within them fully dialed in:

Lab 4.1: Written Subnet Practice #1

Lab 4.2: Written Subnet Practice #2

Lab 4.3: Written Subnet Practice #3

You can find the answers to these labs in Appendix A, “Answers to Written Labs.”

Written Lab 4.1: Written Subnet Practice #1

Write the subnet, broadcast address, and a valid host range for question 1 through question 6. Then answer the remaining questions.

1. 192.168.100.25/30

2. 192.168.100.37/28

3. 192.168.100.66/27

4. 192.168.100.17/29