Allocation Order

Lesson 35 of 46 in Coddy's IP Addressing and Subnetting course.

Why largest first? Because subnets can only start at multiples of their own block size. A /25 can only begin at .0 or .128. Hand out small subnets first and the big one may find every legal starting point blocked, even with plenty of total space left.

Allocating in descending size guarantees each new subnet lands on a legal boundary exactly where the previous one ended. The plan stays gap-free.

Let's extend the previous plan: after Sales (/25) and Engineering (/26), Operations needs 20 hosts, a /27, which slots in at .192.

Challenge

Easy

Print the complete three-team plan for 192.168.100.0/24 in allocation order: Sales (100 hosts), Engineering (50 hosts), Operations (20 hosts). CIDR notation, one per line.

Expected output:

192.168.100.0/25
192.168.100.128/26
192.168.100.192/27

Try it yourself

Terminal

All lessons in IP Addressing and Subnetting

1Bits and Binary

Numbers as Bits Binary to Decimal Powers of Two Recap - Binary Warm-up

4CIDR Notation

Goodbye Classes Reading CIDR Block Sizes Recap - CIDR Reading

7Special Addresses

Private Ranges Loopback Link-Local Zero and Broadcast

10Capstone - The Office

The Floor Plan Sizing Each Team Carving the Block The Router's View Recap - Ship the Plan

2IPv4 Anatomy

Four Octets The 32-Bit View Network and Host Valid or Not Recap - Read an Address

5Inside a Subnet

Network Address Broadcast Address Usable Hosts First and Last Host Recap - Subnet Facts

8Planning Networks

Right-Sizing VLSM Step by StepAllocation OrderChecking for Overlap Recap - Plan a Network

3The Subnet Mask

What a Mask Does Mask to Prefix Prefix to Mask ANDing It Out Recap - Mask Basics

6Subnetting Drills

The Block Size Trick Which Subnet Am I In Splitting a /24 Splitting Again Recap - Subnetting Drills

9IPv6 First Steps

Why IPv6 Reading IPv6 Prefixes in IPv6 Recap - IPv6 Basics

Practice on your own: Terminal playground