Reading CIDR

Lesson 16 of 46 in Coddy's IP Addressing and Subnetting course.

CIDR notation is just address/prefix, and the prefix carries two numbers at once: /n means n network bits and 32 - n host bits.

So /26 is 26 network bits and 6 host bits. /12 is 12 network bits and 20 host bits. The host-bit count is the number you will use most, because it decides how many machines fit.

Whenever you see a slash, compute both numbers reflexively. It takes a second and it unlocks everything that follows.

Challenge

Beginner

For /26 and then /12, print the number of network bits and the number of host bits, each on its own line. Four lines total.

Expected output:

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 ClassesReading CIDRBlock 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 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