11.6.6 Lab – Calculate IPv4 Subnets (Answers)

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.

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