Right-Sizing

Lesson 33 of 46 in Coddy's IP Addressing and Subnetting course.

Network design starts with one question per team: what is the smallest subnet that fits N machines? Find the smallest number of host bits where 2^h - 2 is at least N, then the prefix is 32 - h.

For 50 hosts: 5 bits give 30 (too small), 6 bits give 62 (fits), so a /26. For 200 hosts: 7 bits give 126, 8 give 254, so a /24.

Always leave the minus two in the math. Forgetting it is how someone orders a /26 for exactly 63 machines and discovers the last one has no address.

Challenge

Easy

Print the smallest prefix (with slash) that fits each requirement, one per line, in this order:

50 hosts
200 hosts
2 hosts

Expected output:

/26
/24
/30

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-SizingVLSM Step by Step Allocation Order Checking 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