Lab 03 — IPv4 Addressing and Subnetting

Mission Information

Item	Details
Lab	03
Lab Name	IPv4 Addressing and Subnetting
Track	CompTIA Network+
Difficulty	Beginner–Intermediate
Estimated Time	120–150 minutes
Primary Role	Network Technician / Network Administrator
Environment	Network+ Virtual Lab
Primary Systems	NETPLUS-ADMIN, NETPLUS-CLIENT01, NETPLUS-SERVER01
Primary Tools	Windows/Linux Networking Tools, Calculator, Wireshark
Skills	IPv4, Subnet Masks, CIDR, Binary, Network Address, Broadcast Address, Host Ranges, FLSM, VLSM, Address Planning

Mission Objective: Develop practical IPv4 subnetting skills by calculating networks manually, designing enterprise addressing plans, configuring hosts in different subnets, and troubleshooting addressing mistakes.

Mission Scenario

GHC Enterprise is expanding its network.

The existing environment uses:

10.10.10.0/24

for every system.

The networking team now wants separate networks for:

Users

Servers

Network Management

Guest Devices

Instead of assigning random IP addresses, you must create a structured IPv4 addressing plan.

You need to determine:

How many networks are required?
        ↓
How many hosts are required?
        ↓
Which subnet mask should be used?
        ↓
What is each network address?
        ↓
What is each broadcast address?
        ↓
Which addresses can hosts use?
        ↓
How should the subnets be allocated?

Mission Objectives

By completing this lab, you will be able to:

• understand IPv4 address structure

• identify network and host portions

• understand subnet masks

• convert subnet masks to CIDR notation

• understand binary IPv4 addressing

• calculate network addresses

• calculate broadcast addresses

• calculate usable host ranges

• calculate host capacity

• determine subnet boundaries

• subnet a /24 network

• understand borrowed host bits

• perform fixed-length subnetting

• understand VLSM

• create an enterprise addressing plan

• configure hosts in different subnets

• recognize when routing is required

• troubleshoot incorrect IPv4 configurations

1. Review the Existing Network

Your current environment uses:

Network:
10.10.10.0/24

Systems:

System	Address
NETPLUS-ADMIN	10.10.10.10
NETPLUS-CLIENT01	10.10.10.20
NETPLUS-SERVER01	10.10.10.30

All systems belong to:

10.10.10.0/24

Therefore they can communicate directly.

2. Understand an IPv4 Address

IPv4 addresses contain:

32 bits

divided into four octets:

10.10.10.20

Conceptually:

10        10        10        20
↓         ↓         ↓         ↓
Octet 1   Octet 2   Octet 3   Octet 4

Each octet contains:

8 bits

Therefore:

8 + 8 + 8 + 8
=
32 bits

3. Understand Binary Values

Each octet uses these binary positions:

128  64  32  16  8  4  2  1

Example:

192

becomes:

128 + 64
=
192

Binary:

11000000

4. Convert IPv4 to Binary

Take:

192.168.1.10

Binary representation:

192 = 11000000

168 = 10101000

1   = 00000001

10  = 00001010

Therefore:

11000000.10101000.00000001.00001010

5. Binary Practice

Convert these decimal values to binary:

0
1
10
32
64
128
192
224
240
248
252
254
255

Use:

128 64 32 16 8 4 2 1

as your reference.

6. Understand the Subnet Mask

A subnet mask identifies:

Network Bits

Host Bits

Example:

255.255.255.0

Binary:

11111111.11111111.11111111.00000000

Therefore:

24 Network Bits
8 Host Bits

CIDR notation:

/24

7. Understand CIDR

CIDR expresses the number of network bits.

Examples:

CIDR	Subnet Mask
/8	255.0.0.0
/16	255.255.0.0
/24	255.255.255.0
/25	255.255.255.128
/26	255.255.255.192
/27	255.255.255.224
/28	255.255.255.240
/29	255.255.255.248
/30	255.255.255.252

Memorizing this table is extremely useful for Network+.

8. Understand Network and Host Portions

For:

10.10.10.20/24

conceptually:

10.10.10 | 20
----------+---
 Network   Host

The first 24 bits represent the network.

The remaining 8 bits represent hosts.

9. Identify the Network Address

For:

10.10.10.20/24

the network address is:

10.10.10.0

The network address identifies the subnet itself.

It is not normally assigned to a host.

10. Identify the Broadcast Address

For:

10.10.10.0/24

the broadcast address is:

10.10.10.255

The broadcast address represents all hosts on the subnet for traditional IPv4 broadcast communication.

11. Identify the Usable Host Range

For:

10.10.10.0/24

the usable range is:

10.10.10.1
      ↓
10.10.10.254

Therefore:

Network:
10.10.10.0

First Host:
10.10.10.1

Last Host:
10.10.10.254

Broadcast:
10.10.10.255

12. Calculate Host Capacity

A traditional subnet host calculation is:

2^h - 2

where:

h = host bits

For /24:

32 - 24
=
8 host bits

Therefore:

2^8 - 2
=
256 - 2
=
254 usable hosts

13. Practice Host Capacity

Calculate:

Prefix	Host Bits	Usable Hosts
/24	8	254
/25	7	126
/26	6	62
/27	5	30
/28	4	14
/29	3	6
/30	2	2

This table is worth knowing quickly.

14. Understand Why We Subnet

Imagine one /24 network:

10.10.10.0/24

containing:

Users

Servers

Administrators

Guests

Printers

Infrastructure

This creates one large broadcast domain.

A better design might be:

Users
   ↓
Subnet A

Servers
   ↓
Subnet B

Management
   ↓
Subnet C

Guests
   ↓
Subnet D

Subnetting improves:

• organization

• scalability

• broadcast control

• security segmentation

• troubleshooting

• address management

15. Subnet the /24 into Two Networks

Start with:

10.10.10.0/24

Borrow one host bit.

You now have:

/25

A /25 mask is:

255.255.255.128

The block size is:

256 - 128
=
128

Therefore the subnets are:

10.10.10.0/25

10.10.10.128/25

16. Calculate the First /25

Network:
10.10.10.0

First Host:
10.10.10.1

Last Host:
10.10.10.126

Broadcast:
10.10.10.127

17. Calculate the Second /25

Network:
10.10.10.128

First Host:
10.10.10.129

Last Host:
10.10.10.254

Broadcast:
10.10.10.255

18. Understand the Subnet Boundary

For /25:

Block Size:
128

Boundaries:

0
128

Therefore:

0–127

128–255

19. Subnet the /24 into Four Networks

Borrow two host bits:

/24
 ↓
/26

Mask:

255.255.255.192

Block size:

256 - 192
=
64

Subnet boundaries:

0
64
128
192

20. Calculate the Four /26 Networks

Subnet 1

Network:
10.10.10.0/26

Hosts:
10.10.10.1–10.10.10.62

Broadcast:
10.10.10.63

Subnet 2

Network:
10.10.10.64/26

Hosts:
10.10.10.65–10.10.10.126

Broadcast:
10.10.10.127

Subnet 3

Network:
10.10.10.128/26

Hosts:
10.10.10.129–10.10.10.190

Broadcast:
10.10.10.191

Subnet 4

Network:
10.10.10.192/26

Hosts:
10.10.10.193–10.10.10.254

Broadcast:
10.10.10.255

21. Build the Subnet Table

Subnet	Network	First Host	Last Host	Broadcast
1	10.10.10.0/26	.1	.62	.63
2	10.10.10.64/26	.65	.126	.127
3	10.10.10.128/26	.129	.190	.191
4	10.10.10.192/26	.193	.254	.255

22. Understand the Block-Size Method

For an interesting subnet octet:

Block Size
=
256 - Subnet Mask Value

Example /27:

255.255.255.224

Therefore:

256 - 224
=
32

Subnet boundaries:

0
32
64
96
128
160
192
224

23. Calculate /27 Networks

Each /27 traditionally provides:

30 usable hosts

Example:

10.10.10.64/27

Range:

Network:
10.10.10.64

First:
10.10.10.65

Last:
10.10.10.94

Broadcast:
10.10.10.95

24. Subnet Identification Challenge

Given:

10.10.10.78/27

Block size:

32

Boundaries:

0
32
64
96
...

78 falls between:

64–95

Therefore:

Network:
10.10.10.64

Broadcast:
10.10.10.95

First Host:
10.10.10.65

Last Host:
10.10.10.94

25. Practice Problem 1

Calculate:

192.168.10.140/26

Determine:

Subnet Mask:

Network Address:

First Host:

Last Host:

Broadcast:

Usable Hosts:

Solution

/26:

255.255.255.192

Block:

64

Boundaries:

0
64
128
192

140 belongs to:

128–191

Therefore:

Network:
192.168.10.128

First:
192.168.10.129

Last:
192.168.10.190

Broadcast:
192.168.10.191

Usable Hosts:
62

26. Practice Problem 2

Calculate:

172.16.5.200/27

Use:

/27
=
255.255.255.224

Block:
32

Determine the answer before continuing.

Solution

Boundaries:

0
32
64
96
128
160
192
224

Therefore:

Network:
172.16.5.192

First Host:
172.16.5.193

Last Host:
172.16.5.222

Broadcast:
172.16.5.223

Usable Hosts:
30

27. Practice Problem 3

Calculate:

192.168.50.118/28

/28:

255.255.255.240

Block:

16

Boundaries:

0
16
32
48
64
80
96
112
128
...

Therefore:

Network:
192.168.50.112

First:
192.168.50.113

Last:
192.168.50.126

Broadcast:
192.168.50.127

Usable Hosts:
14

28. Determine Whether Hosts Are on the Same Subnet

Consider:

Host A:
192.168.1.10/24

Host B:
192.168.1.200/24

Both belong to:

192.168.1.0/24

Therefore:

Same Subnet

They can communicate directly at Layer 2.

29. Different Subnet Example

Consider:

Host A:
192.168.1.10/25

Host B:
192.168.1.200/25

Host A belongs to:

192.168.1.0/25

Host B belongs to:

192.168.1.128/25

Therefore:

Different Subnets

Communication requires routing.

30. Configure the Lab into Separate Subnets

Now modify the environment.

Use:

ADMIN Network:
10.10.10.0/26

SERVER Network:
10.10.10.64/26

Configure:

NETPLUS-ADMIN:
10.10.10.10/26

NETPLUS-CLIENT01:
10.10.10.20/26

NETPLUS-SERVER01:
10.10.10.70/26

31. Test Connectivity

From NETPLUS-ADMIN:

ping 10.10.10.20

This should work because both are in:

10.10.10.0/26

Now:

ping 10.10.10.70

Without a router between the two subnets, communication should fail.

32. Explain Why the Server Is Unreachable

ADMIN:

10.10.10.10/26

belongs to:

10.10.10.0–63

SERVER:

10.10.10.70/26

belongs to:

10.10.10.64–127

Therefore:

ADMIN
10.10.10.0/26
      ↓
    Router
      ↓
SERVER
10.10.10.64/26

A Layer 3 device is required.

33. Observe the Routing Decision

On Linux:

ip route

The host knows only its directly connected subnet.

Without a route/default gateway to the server subnet:

Destination
=
Unreachable through current local path

This is an important Network+ concept:

Subnetting creates network boundaries. Routing connects those boundaries.

34. Restore the Original Lab

Restore:

NETPLUS-ADMIN:
10.10.10.10/24

NETPLUS-CLIENT01:
10.10.10.20/24

NETPLUS-SERVER01:
10.10.10.30/24

Verify:

ping 10.10.10.20
ping 10.10.10.30

35. Understand Fixed-Length Subnetting

Fixed-Length Subnet Masking uses the same prefix for every subnet.

Example:

10.10.10.0/24

split into:

10.10.10.0/26
10.10.10.64/26
10.10.10.128/26
10.10.10.192/26

Every subnet provides:

62 usable addresses

This is simple but may waste addresses.

36. Enterprise Addressing Scenario

GHC Enterprise needs:

Users:
50 hosts

Servers:
25 hosts

Management:
10 hosts

Guest:
10 hosts

Using four /26 networks would provide:

62 + 62 + 62 + 62

usable capacity.

But Management only needs:

10 hosts

Giving it 62 addresses is inefficient.

This introduces:

VLSM

37. Understand VLSM

VLSM means:

Variable Length Subnet Masking

Instead of every subnet having the same size:

/26
/26
/26
/26

we can use:

/26
/27
/28
/28

based on requirements.

38. VLSM Rule — Start with the Largest Network

Requirements:

Users:
50

Servers:
25

Management:
10

Guest:
10

Order:

50
 ↓
25
 ↓
10
 ↓
10

Allocate the largest subnet first.

39. Allocate the Users Network

Need:

50 hosts

/27 provides only:

30

Not enough.

/26 provides:

62

Therefore:

Users:
10.10.10.0/26

Range:

10.10.10.1–10.10.10.62

Broadcast:

10.10.10.63

40. Allocate the Server Network

Need:

25 hosts

/27 provides:

30

Therefore:

Servers:
10.10.10.64/27

Range:

10.10.10.65–10.10.10.94

Broadcast:

10.10.10.95

41. Allocate Management

Need:

10 hosts

/28 provides:

14

Therefore:

Management:
10.10.10.96/28

Range:

10.10.10.97–10.10.10.110

Broadcast:

10.10.10.111

42. Allocate Guest

Need:

10 hosts

Use another /28:

Guest:
10.10.10.112/28

Range:

10.10.10.113–10.10.10.126

Broadcast:

10.10.10.127

43. Build the VLSM Address Plan

Department	Hosts	Network	Usable Range	Broadcast
Users	50	10.10.10.0/26	.1–.62	.63
Servers	25	10.10.10.64/27	.65–.94	.95
Management	10	10.10.10.96/28	.97–.110	.111
Guest	10	10.10.10.112/28	.113–.126	.127

Addresses from:

10.10.10.128

onward remain available for future networks.

44. Understand Why VLSM Is Better

Without VLSM:

Every Network
      ↓
Same Size

With VLSM:

Business Requirement
      ↓
Required Hosts
      ↓
Appropriate Subnet Size

This reduces address waste.

45. Design Gateway Addresses

A common convention is to use the first usable address as the gateway.

Example:

Network	Gateway
Users	10.10.10.1
Servers	10.10.10.65
Management	10.10.10.97
Guest	10.10.10.113

This is a design convention, not an IPv4 requirement.

46. Reserve Infrastructure Addresses

You may reserve predictable addresses.

Example:

Gateway:
First usable

Network devices:
Next addresses

Servers:
Reserved range

DHCP:
Remaining client range

Example Users subnet:

10.10.10.0/26

Gateway:
10.10.10.1

Infrastructure:
10.10.10.2–10.10.10.9

Clients:
10.10.10.10–10.10.10.62

47. Private IPv4 Address Ranges

Know the RFC1918 private ranges:

10.0.0.0/8

172.16.0.0/12

192.168.0.0/16

These are commonly used inside private networks.

48. Recognize APIPA

Windows may automatically assign an address from:

169.254.0.0/16

when automatic addressing is expected but DHCP is unavailable.

Example:

169.254.27.83

This can be a major troubleshooting clue.

49. Recognize Loopback

IPv4 loopback range:

127.0.0.0/8

Most commonly:

127.0.0.1

used to refer to the local host.

50. Recognize the Default Route

A default IPv4 route is commonly represented as:

0.0.0.0/0

Conceptually:

If no more specific route exists
        ↓
Use the default route

51. Understand Longest Prefix Match

Suppose a router knows:

10.0.0.0/8

10.10.0.0/16

10.10.10.0/24

Destination:

10.10.10.50

matches all three.

The router prefers:

10.10.10.0/24

because it is the most specific route.

This is called:

Longest Prefix Match

52. Troubleshooting Scenario — Wrong Subnet Mask

Configure:

NETPLUS-ADMIN:
10.10.10.10/24

NETPLUS-CLIENT01:
10.10.10.20/26

Both addresses may appear similar.

But their understanding of the network boundary is different.

Use:

ip addr
ip route

and:

ipconfig
route print

to investigate.

53. Why Incorrect Masks Are Dangerous

Consider:

Host A:
10.10.10.10/24

Host A believes:

10.10.10.0–255

is local.

Host B:

10.10.10.70/26

believes only:

10.10.10.64–127

is local.

Mismatched masks can create confusing or asymmetric communication behavior.

54. Troubleshooting Scenario — Network Address Assigned

Try to reason about:

10.10.10.64/26

This is:

Network Address

for:

10.10.10.64/26

It should not normally be assigned to a host.

55. Troubleshooting Scenario — Broadcast Address Assigned

For:

10.10.10.64/26

the broadcast is:

10.10.10.127

It should not be assigned as a normal host address.

56. Troubleshooting Scenario — Wrong Gateway

Suppose:

Host:
10.10.10.20/26

Gateway:
10.10.10.100

Host network:

10.10.10.0/26

usable range:

10.10.10.1–62

The configured gateway:

10.10.10.100

is not in the host’s subnet.

This is an obvious configuration problem.

57. Troubleshooting Scenario — Duplicate IP

Configure the same address on two lab systems temporarily:

10.10.10.20

Observe possible symptoms such as:

• intermittent connectivity

• ARP changes

• duplicate-address warnings

• inconsistent communication

Restore unique addresses immediately after the exercise.

58. Inspect ARP During Addressing Problems

Use:

ip neigh

or:

arp -a

A duplicate IP can result in one IP being associated with unexpected MAC addresses over time.

59. Capture ARP with Wireshark

Apply:

arp

Observe how systems attempt to resolve local addresses.

This reinforces the relationship:

Subnet Decision
      ↓
Local Destination
      ↓
ARP
      ↓
MAC Address

60. Build an IPv4 Troubleshooting Workflow

Use:

Interface Up?
      ↓
Correct IPv4 Address?
      ↓
Correct Subnet Mask?
      ↓
Correct Network?
      ↓
Valid Host Address?
      ↓
Correct Gateway?
      ↓
Duplicate IP?
      ↓
Correct Route?
      ↓
ARP Working?
      ↓
Connectivity Test

61. Subnetting Challenge 1

Given:

192.168.100.0/24

Create:

4 equal subnets

Determine:

New Prefix:

Subnet Mask:

Network Addresses:

Broadcast Addresses:

Host Ranges:

Answer

Four subnets require borrowing:

2 bits

Therefore:

/26

Networks:

192.168.100.0/26

192.168.100.64/26

192.168.100.128/26

192.168.100.192/26

62. Subnetting Challenge 2

Given:

172.16.20.0/24

create:

8 equal subnets

Borrow:

3 bits

New prefix:

/27

Block:

32

Networks:

172.16.20.0/27
172.16.20.32/27
172.16.20.64/27
172.16.20.96/27
172.16.20.128/27
172.16.20.160/27
172.16.20.192/27
172.16.20.224/27

63. Subnetting Challenge 3

Determine the network containing:

192.168.20.177/28

/28 block:

16

Boundaries:

...
144
160
176
192
...

Therefore:

Network:
192.168.20.176

First:
192.168.20.177

Last:
192.168.20.190

Broadcast:
192.168.20.191

64. VLSM Mission Challenge

You receive:

192.168.50.0/24

Requirements:

Engineering:
100 hosts

Sales:
50 hosts

Servers:
20 hosts

Management:
10 hosts

Determine an efficient VLSM plan.

65. VLSM Challenge — Engineering

Need:

100

/25 provides:

126

Assign:

192.168.50.0/25

Range:

192.168.50.1–126

Broadcast:

192.168.50.127

66. VLSM Challenge — Sales

Need:

50

Use:

/26

Assign:

192.168.50.128/26

Range:

192.168.50.129–190

Broadcast:

192.168.50.191

67. VLSM Challenge — Servers

Need:

20

Use:

/27

Assign:

192.168.50.192/27

Range:

192.168.50.193–222

Broadcast:

192.168.50.223

68. VLSM Challenge — Management

Need:

10

Use:

/28

Assign:

192.168.50.224/28

Range:

192.168.50.225–238

Broadcast:

192.168.50.239

69. Final VLSM Plan

Network	Hosts Needed	Prefix	Address Range
Engineering	100	/25	192.168.50.0–127
Sales	50	/26	192.168.50.128–191
Servers	20	/27	192.168.50.192–223
Management	10	/28	192.168.50.224–239

Remaining:

192.168.50.240–255

can be reserved for future subnetting.

70. Build an Enterprise Addressing Document

Use:

# IPv4 Addressing Plan

## Parent Network

Network:

Prefix:

Subnet Mask:

## Subnet 1

Purpose:

Network:

Prefix:

Subnet Mask:

Gateway:

First Host:

Last Host:

Broadcast:

Host Capacity:

## Subnet 2

Purpose:

Network:

Prefix:

Subnet Mask:

Gateway:

First Host:

Last Host:

Broadcast:

Host Capacity:

## Reserved Addresses

Document infrastructure reservations.

## DHCP Range

Document planned dynamic addresses.

## Static Addresses

Document servers and network infrastructure.

71. Create the Lab Workspace

On NETPLUS-ADMIN:

mkdir -p ~/NetworkPlus-Labs/LAB03/{Screenshots,Configs,Calculations,Notes}

Create:

touch ~/NetworkPlus-Labs/LAB03/Notes/lab03-notes.md

and:

touch ~/NetworkPlus-Labs/LAB03/Calculations/subnetting-practice.md

72. Document Your Calculations

Use:

# LAB03 — IPv4 Subnetting Calculations

## Exercise 1

IP:

Prefix:

Subnet Mask:

Block Size:

Network:

First Host:

Last Host:

Broadcast:

Host Capacity:

## Exercise 2

IP:

Prefix:

Subnet Mask:

Block Size:

Network:

First Host:

Last Host:

Broadcast:

Host Capacity:

## VLSM Exercise

Parent Network:

### Requirements

Department:
Hosts:

### Allocation

Network:

Prefix:

Gateway:

Host Range:

Broadcast:

73. Evidence to Capture

Capture:

01-original-ip-configuration.png

02-ipv4-binary-calculation.png

03-cidr-mask-table.png

04-24-subnet-calculation.png

05-25-subnet-calculation.png

06-26-subnet-calculation.png

07-27-subnet-calculation.png

08-subnet-boundaries.png

09-admin-26-configuration.png

10-client-26-configuration.png

11-server-second-subnet.png

12-same-subnet-ping.png

13-different-subnet-failure.png

14-routing-table.png

15-restored-24-network.png

16-vlsm-calculation.png

17-enterprise-address-plan.png

18-wrong-subnet-mask.png

19-wrong-gateway.png

20-arp-investigation.png

21-final-subnet-table.png

74. Mission Challenge Questions

Answer without using a subnet calculator:

1. How many bits are in an IPv4 address?

2. How many bits are in one octet?

3. What does /24 mean?

4. What mask corresponds to /26?

5. How many usable hosts does /26 traditionally provide?

6. What mask corresponds to /27?

7. What is the block size of /27?

8. What is the network address of 192.168.1.75/26?

9. What is its broadcast address?

10. What is its usable host range?

11. Are 192.168.1.10/25 and 192.168.1.150/25 in the same subnet?

12. What is VLSM?

13. Why allocate the largest VLSM subnet first?

14. What are the RFC1918 private ranges?

15. What does 169.254.x.x commonly indicate?

16. What is 127.0.0.1?

17. What does 0.0.0.0/0 represent in routing?

18. Can two different subnets communicate without Layer 3 routing?

19. Why is an incorrect subnet mask dangerous?

20. Why should network and broadcast addresses not normally be assigned to hosts?

75. Validation Checklist

IPv4 Fundamentals

• 32-bit IPv4 structure understood

• Octets understood

• Binary values reviewed

• Network and host portions understood

• Subnet masks understood

• CIDR notation understood

Subnet Calculations

• Network address calculated

• Broadcast address calculated

• First usable host calculated

• Last usable host calculated

• Host capacity calculated

• Block-size method understood

• /25 calculated

• /26 calculated

• /27 calculated

• /28 calculated

Practical Configuration

• Hosts configured in same subnet

• Same-subnet connectivity verified

• Server moved into different subnet

• Cross-subnet failure observed without routing

• Routing requirement understood

• Original lab addressing restored

VLSM

• FLSM understood

• VLSM understood

• Requirements ordered largest to smallest

• Appropriate prefix selected for each requirement

• VLSM address plan completed

• Address waste considered

Troubleshooting

• Wrong IP investigated

• Wrong subnet mask investigated

• Invalid gateway recognized

• Network address recognized

• Broadcast address recognized

• Duplicate IP behavior understood

• ARP reviewed

• Routing table reviewed

Documentation

• Subnet calculations documented

• Enterprise addressing plan created

• Evidence captured

• Final subnet table completed

76. Mission Review

In this mission, you moved from:

IP Address

to understanding:

IP Address
     ↓
Subnet Mask
     ↓
CIDR Prefix
     ↓
Network Address
     ↓
Subnet Boundary
     ↓
Usable Host Range
     ↓
Broadcast Address

You then moved from a single network:

10.10.10.0/24

to multiple logical networks:

Users
   ↓
10.10.10.0/26

Servers
   ↓
10.10.10.64/27

Management
   ↓
10.10.10.96/28

Guest
   ↓
10.10.10.112/28

The key networking relationship is:

Same Subnet
     ↓
Direct Layer 2 Communication

while:

Different Subnet
      ↓
Layer 3 Routing Required

Subnetting is not simply an exam calculation. It defines network boundaries and directly influences routing, segmentation, security, scalability, and troubleshooting.

Skills Developed

After completing this mission, you should be able to:

• interpret IPv4 addresses

• convert common decimal and binary values

• interpret subnet masks

• convert subnet masks to CIDR

• calculate network addresses

• calculate broadcast addresses

• calculate usable host ranges

• determine subnet boundaries

• calculate host capacity

• perform /25, /26, /27, and /28 subnetting

• determine whether two hosts share a subnet

• perform fixed-length subnetting

• design basic VLSM networks

• recognize private IPv4 ranges

• recognize APIPA and loopback addressing

• understand default routes

• understand longest-prefix matching

• identify common IPv4 configuration errors

• create an enterprise IPv4 addressing plan

What’s Next?

Lab 04 — IPv6 Addressing and Connectivity

IPv4 subnetting gives you the foundation for understanding logical network boundaries.

The next mission introduces IPv6 and how modern networks operate with a 128-bit address space.

You will work with:

• IPv6 address structure

• hexadecimal notation

• IPv6 address compression

• prefix lengths

• global unicast addresses

• link-local addresses

• multicast

• loopback

• unspecified addresses

• IPv6 interface configuration

• Neighbor Discovery

• ICMPv6

• Router Advertisement concepts

• SLAAC concepts

• dual-stack networking

• IPv6 routing

• IPv6 packet capture

• IPv6 troubleshooting

The progression becomes:

IPv4
   ↓
32-Bit Addressing
   ↓
Subnetting
   ↓
Network Boundaries
   ↓
IPv6
   ↓
128-Bit Addressing
   ↓
Modern IP Connectivity

➡️ Next: Lab 04 — IPv6 Addressing and Connectivity