Learning Objectives

• Apply all subnetting concepts to mixed problems
• Practice speed calculations for exam conditions
• Solve real-world subnet design scenarios

Mixed Practice Questions

Try these questions to test everything you've learned. The CCNA target is 30-60 seconds per question.

Real-World Scenario

Problem: Your company has the block 192.168.0.0/22. You need:

• One subnet for servers: minimum 400 addresses
• One subnet for employees: minimum 200 addresses
• One subnet for guests: minimum 50 addresses
• Future growth: 20% headroom

Step 1: Calculate required sizes with headroom

| Segment | Current Need | With 20% Headroom | |---------|-------------|------------------| | Servers | 400 | 480 → need 512 (/23) | | Employees | 200 | 240 → need 256 (/24) | | Guests | 50 | 60 → need 64 (/26) |

Step 2: Allocate from largest to smallest

Starting from 192.168.0.0/22 (1024 addresses):

1. Servers: 192.168.0.0/23 (512 addresses: 192.168.0.0 - 192.168.1.255)
2. Employees: 192.168.2.0/24 (256 addresses: 192.168.2.0 - 192.168.2.255)
3. Guests: 192.168.3.0/26 (64 addresses: 192.168.3.0 - 192.168.3.63)

Step 3: Remaining space: 192.168.3.64/26 through 192.168.3.255/24 — 192 addresses for future use.

Tips for Exam Success

1. Know your block sizes — /24 = 256, /25 = 128, /26 = 64, /27 = 32, /28 = 16, /29 = 8, /30 = 4
2. The −2 rule — Never forget to subtract 2 for network and broadcast
3. Interesting octet — Identify which octet the subnet boundary falls in
4. Multiples of block size — Network boundaries are always multiples
5. Practice daily — Even 5 minutes of subnetting practice keeps your speed sharp

Use the Subnet Calculator with "Show Steps" enabled to check your work and see the full breakdown of any CIDR.

Course Complete

Congratulations! You've completed the Subnetting Mastery course. You now understand:

• Why subnetting exists and how CIDR works
• How to read prefix lengths and subnet masks
• How to calculate network/broadcast/host addresses
• How to work with any prefix from /8 to /32
• How to design real-world subnet plans

Continue practicing with the Subnetting Quiz and Subnet Randomizer tools to keep your skills sharp.