Master subnetting with hands-on exercises from basic to advanced
Subnetting is one of the highest-value skills on the CCNA 200-301 exam. This tool generates problems and walks you through solutions step by step. The CCNA exam requires you to calculate subnet addresses, broadcast addresses, usable host ranges, and the number of hosts per subnet quickly and accurately.
Key concepts to master: CIDR notation (/24, /25, /26...), subnet mask in dotted-decimal, network address (all host bits = 0), broadcast address (all host bits = 1), usable host range (network+1 to broadcast-1), number of subnets (2^borrowed bits), and hosts per subnet (2^host bits - 2). VLSM allows different-sized subnets for different networks.
Practice tip: Aim to calculate any /24 through /30 subnet in under 30 seconds using the block size method: subtract the last non-zero subnet mask octet from 256 to find block size, then count up in multiples.
Learn to subnet a Class C network into smaller subnets
Practice converting between decimal and CIDR notation
Subnet a Class B network for multiple departments
Use Variable Length Subnet Masking for efficient addressing
Design subnets based on specific host requirements
Summarize multiple networks into a single route
Design a complete network using VLSM for multiple sites
Practice subnetting with IPv6 addresses
Master binary to decimal conversion for subnetting
Identify and fix subnet configuration errors
Calculate subnet details instantly
| CIDR | Subnet Mask | Hosts |
|---|---|---|
| /24 | 255.255.255.0 | 254 |
| /25 | 255.255.255.128 | 126 |
| /26 | 255.255.255.192 | 62 |
| /27 | 255.255.255.224 | 30 |
| /28 | 255.255.255.240 | 14 |
| /29 | 255.255.255.248 | 6 |
| /30 | 255.255.255.252 | 2 |