11.6.6 Lab – Calculate IPv4 Subnets
Objectives
- Part 1: Determine IPv4 Address Subnetting
- Part 2: Calculate IPv4 Address Subnetting
Background / Scenario
The ability to work with IPv4 subnets and determine network and host information based on a given IP address and subnet mask is critical to understanding how IPv4 networks operate. The first part is designed to reinforce how to compute network IP address information from a given IP address and subnet mask. When given an IP address and subnet mask, you will be able to determine other information about the subnet.
Instructor Note: This activity can be done in class or assigned as homework. If the assignment is done in class, you may wish to have students work alone or in teams of 2 students each. It is suggested that the first problem is done together in class to give students guidance as to how to proceed for the rest of the assignment.
The public IP addresses used in this lab are owned by Cisco.
Required Resources
- 1 PC (Windows with Internet access)
- Optional: IPv4 address calculator
Instructions
Fill out the tables below with appropriate answers given the IPv4 address, original subnet mask, and new subnet mask.
Problem 1:
| Given: | |
|---|---|
| Host IP Address: | 192.168.200.139 |
| Original Subnet Mask | 255.255.255.0 |
| New Subnet Mask: | 255.255.255.224 |
| Find: | |
|---|---|
| Number of Subnet Bits | 3 |
| Number of Subnets Created | 8 |
| Number of Host Bits per Subnet | 5 |
| Number of Hosts per Subnet | 30 |
| Network Address of this Subnet | 192.168.200.128 |
| IPv4 Address of First Host on this Subnet | 192.168.200.129 |
| IPv4 Address of Last Host on this Subnet | 192.168.200.158 |
| IPv4 Broadcast Address on this Subnet | 192.168.200.159 |
Problem 2:
| Given: | |
|---|---|
| Host IP Address: | 10.101.99.228 |
| Original Subnet Mask | 255.0.0.0 |
| New Subnet Mask: | 255.255.128.0 |
| Find: | |
|---|---|
| Number of Subnet Bits | 9 |
| Number of Subnets Created | 512 |
| Number of Host Bits per Subnet | 15 |
| Number of Hosts per Subnet | 32,766 |
| Network Address of this Subnet | 10.101.0.0 |
| IPv4 Address of First Host on this Subnet | 10.101.0.1 |
| IPv4 Address of Last Host on this Subnet | 10.101.127.254 |
| IPv4 Broadcast Address on this Subnet | 10.101.127.255 |
Problem 3:
| Given: | |
|---|---|
| Host IP Address: | 172.22.32.12 |
| Original Subnet Mask | 255.255.0.0 |
| New Subnet Mask: | 255.255.224.0 |
| Find: | |
|---|---|
| Number of Subnet Bits | 3 |
| Number of Subnets Created | 8 |
| Number of Host Bits per Subnet | 13 |
| Number of Hosts per Subnet | 8,190 |
| Network Address of this Subnet | 172.22.32.0 |
| IPv4 Address of First Host on this Subnet | 172.22.32.1 |
| IPv4 Address of Last Host on this Subnet | 172.22.63.254 |
| IPv4 Broadcast Address on this Subnet | 172.22.63.255 |
Problem 4:
| Given: | |
|---|---|
| Host IP Address: | 192.1681.245 |
| Original Subnet Mask | 255.255.255.0 |
| New Subnet Mask: | 255.255.255.252 |
| Find: | |
|---|---|
| Number of Subnet Bits | 6 |
| Number of Subnets Created | 64 |
| Number of Host Bits per Subnet | 2 |
| Number of Hosts per Subnet | 2 |
| Network Address of this Subnet | 192.168.1.244 |
| IPv4 Address of First Host on this Subnet | 192.168.1.245 |
| IPv4 Address of Last Host on this Subnet | 192.168.1.246 |
| IPv4 Broadcast Address on this Subnet | 195.168.1.247 |
Problem 5:
| Given: | |
|---|---|
| Host IP Address: | 128.107.0.55 |
| Original Subnet Mask | 255.255.0.0 |
| New Subnet Mask: | 255.255.255.0 |
| Find: | |
|---|---|
| Number of Subnet Bits | 8 |
| Number of Subnets Created | 256 |
| Number of Host Bits per Subnet | 8 |
| Number of Hosts per Subnet | 254 |
| Network Address of this Subnet | 128.107.0.0 |
| IPv4 Address of First Host on this Subnet | 128.107.0.1 |
| IPv4 Address of Last Host on this Subnet | 128.107.0.254 |
| IPv4 Broadcast Address on this Subnet | 128.107.0.255 |
Problem 6:
| Given: | |
|---|---|
| Host IP Address: | 192.135.250.180 |
| Original Subnet Mask | 255.255.255.0 |
| New Subnet Mask: | 255.255.255.248 |
| Find: | |
|---|---|
| Number of Subnet Bits | 5 |
| Number of Subnets Created | 32 |
| Number of Host Bits per Subnet | 3 |
| Number of Hosts per Subnet | 6 |
| Network Address of this Subnet | 192.135.250.176 |
| IPv4 Address of First Host on this Subnet | 192.135.250.177 |
| IPv4 Address of Last Host on this Subnet | 192.135.250.182 |
| IPv4 Broadcast Address on this Subnet | 192.135.250.183 |
Reflection Question
Why is the subnet mask so important when analyzing an IPv4 address?
The subnet mask determines everything about the address: the network, number of host bits, number of hosts and the broadcast address. Merely looking at an IPv4 address tells you nothing. You need the subnet mask to fill in all the important pieces of information.
