Module 1.1 - OSI and TCP/IP Models

Module 1.2 - Devices & Protocols in Relation to OSI Model

Module 1.3

Module 1.4

Module 1.5 and 1.6

Module 1.7

Module 1.8

Module 1.9

Module 2.1

Module 2.2

Module 2.3

Module 2.4

Module 2.5

Module 2.6

Module 3.1 and 3.2

Module 3.3

Module 3.4

Module 3.5

Module 3.7

Module 3.8

Module 4.1

Module 4.2

Module 4.3

Module 4.4

Module 4.5

Module 4.6

Module 5.1

Module 5.2

Module 5.3

Module 5.4

Module 5.5

Module 5.6


Invite Friends
Facebook Twitter Google+ LinkedIn Email
Virtual Practice Lab
Practice Test

Classless Inter Domain Routing (CIDR)

This lesson discusses Classless Inter Domain Routing (CIDR). CIDR allows us to have variable-length subnet masks. Subnet masks within CIDR are not within the standard classes of A,B or C and CIDR notation is used when standard subnet masks do not work and allows us to break up subnet masks and work with IP addresses.

Watch the Course Intro Video
Learn on the go.
The app designed for the modern cyber security professional.
Get it on Google PlayGet it on the App Store
Practice Labs and Exam Vouchers

Congratulations! You're taking the first step to getting certified. Get some hands on experience with available practice labs OR save some money, support Cybrary, and purchase discounted exam vouchers. Ready to earn your next industry certification? Join cyber security's largest community and start learning today.


Upcoming Industry Events

Get more out of Cybrary
Reach an audience of 1,500,000+ IT and cyber professionals, including the world's top companies
Create impact at a scale by reaching a global audience
Build your personal brand
Supplement or replace your income (average instructor makes ~$1,000 - $2,000/month)
Access the world's largest talent pool of cyber security professionals, and receive candidates with pre-assessed technical skills
Eliminate the pain and costs of technical vetting
Receive candidate skill profiles highlighting knowledge and technical proficiency
Reach active and passive candidates; and, fill your pipeline with pre-vetted, qualified cyber professionals
Get a Job
Work with a dedicated mentor to help you select the career that's right for you, and get a job at one of the world's top companies.
Receive all the training and assessments you need to prepare for the job
Work with a dedicated Mentor
Get placed through Cybrary for jobs earning average salaries of $116,000/yr

Our Revolution

We believe Cyber Security training should be free, for everyone, FOREVER. Everyone, everywhere, deserves the OPPORTUNITY to learn, begin and grow a career in this fascinating field. Therefore, Cybrary is a free community where people, companies and training come together to give everyone the ability to collaborate in an open source way that is revolutionizing the cyber security educational experience.

Cybrary On The Go

Get the Cybrary app for Android for online and offline viewing of our lessons.

Get it on Google Play

Support Cybrary

Donate Here to Get This Month's Donor Badge

Skip to toolbar

We recommend always using caution when following any link

Are you sure you want to continue?