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Subnetting Practice Lab

Calculate network addresses, broadcast addresses, host ranges, and usable hosts from CIDR notation

60 minutes Beginner to Intermediate 7 Tasks
R

Quick Reference: Subnet Cheat Sheet

Keep this open as you work
CIDRSubnet MaskWildcardTotal IPsUsable Hosts
/24255.255.255.00.0.0.255256254
/25255.255.255.1280.0.0.127128126
/26255.255.255.1920.0.0.636462
/27255.255.255.2240.0.0.313230
/28255.255.255.2400.0.0.151614
/29255.255.255.2480.0.0.786
/30255.255.255.2520.0.0.342
Method: Network address = IP AND subnet mask. Broadcast = Network OR wildcard mask. First host = Network + 1. Last host = Broadcast - 1. Usable hosts = 2^(32-prefix) - 2.
1

/24 Network Calculation

Beginner
Given: A host with IP address 192.168.10.47/24. Calculate the network properties.
Host IP: 192.168.10.47 CIDR: /24 Mask: 255.255.255.0
2

/26 Network Calculation

Beginner
Given: A host with IP address 10.0.5.130/26. Calculate the network properties.
Host IP: 10.0.5.130 CIDR: /26 Mask: 255.255.255.192 Block size: 64 (256 - 192)
3

/28 Network Calculation

Intermediate
Given: A host with IP address 172.16.20.100/28. Calculate the network properties.
Host IP: 172.16.20.100 CIDR: /28 Mask: 255.255.255.240 Block size: 16 (256 - 240)
4

/30 Point-to-Point Link

Intermediate
Given: A router interface with IP address 10.0.0.9/30. This is a point-to-point WAN link.
Host IP: 10.0.0.9 CIDR: /30 Mask: 255.255.255.252 Block size: 4 (256 - 252) Note: /30 subnets provide exactly 2 usable IPs — perfect for router-to-router links.
5

/27 Server Subnet

Intermediate
Given: A server with IP address 192.168.1.200/27. Calculate all subnet details.
Host IP: 192.168.1.200 CIDR: /27 Mask: 255.255.255.224 Block size: 32 (256 - 224)
6

Subnet Design Challenge

Advanced
Scenario: You have been given the network 172.16.0.0/16. Design subnets for 3 departments: Sales (50 hosts), Engineering (200 hosts), and Management (12 hosts). What is the smallest CIDR prefix for each?
Available network: 172.16.0.0/16 Department needs: Sales: 50 hosts => need at least 52 IPs Engineering: 200 hosts => need at least 202 IPs Management: 12 hosts => need at least 14 IPs Remember: choose the smallest subnet that fits (most specific prefix).
Design Tip: Sales needs 50 hosts: 2^6 = 64 IPs (62 usable) => /26. Engineering needs 200 hosts: 2^8 = 256 IPs (254 usable) => /24. Management needs 12 hosts: 2^4 = 16 IPs (14 usable) => /28.
7

VLSM Supernet Challenge

Advanced
Given: Two adjacent /24 networks: 10.10.0.0/24 and 10.10.1.0/24. Can they be summarized into a single route? What would the summary be?
Network 1: 10.10.0.0/24 (10.10.0.0 - 10.10.0.255) Network 2: 10.10.1.0/24 (10.10.1.0 - 10.10.1.255) Question: What single CIDR block covers both networks exactly? Binary of the 3rd octet: 0 = 00000000 1 = 00000001 They differ only in the last bit of octet 3.