← IP Addressing & Subnetting learning pathIP Addressing & Subnetting · Module 7 of 10
VLSM
Use variable-length subnet masks to avoid waste.
📖 Key ideas
- VLSM uses different subnet sizes in one network.
- Allocate the largest requirement first.
- Example: 100, 50, 20 hosts from 192.168.1.0/24 → /25, /26, /27.
- Point-to-point router links use /30 or /31.
- Saves addresses compared to equal-size subnets.
💡 Real-life example: VLSM is cutting a cake into slices sized for each guest's appetite, biggest first.
VLSMVariable Length Subnet Masking
Largest firstAllocate biggest subnet first
/30Subnet with 2 usable hosts
Address wasteUnused addresses in subnets