From the course: VPC Networking on AWS: Configuration, Security, and Connectivity

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CIDR blocks

CIDR blocks - Amazon Web Services (AWS) Tutorial

From the course: VPC Networking on AWS: Configuration, Security, and Connectivity

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CIDR blocks

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- [Instructor] In this lesson, we're going to talk about your favorite topic, CIDR blocks. Okay, it's not your favorite topic, but it's necessary to understand what a CIDR block actually is. At AWS, when you create a virtual private cloud, you have to define the range of addresses that are going to be used. For this VPC, the address of 10.4.16.0/20, the slash 20 is the important part. Think of this slash 20 as defining the total number of addresses that can be used in this network, 4,094. For the public subnet, a different scheme following the 10.4.16.0, but then the slash says, oh, I want this many addresses out of the total number of 4,000 and change. I want 30. That's the maximum I can have with that slash 27. So the slash is important. It does the work. Slash 24 says, oh, I want 251 addresses. Now what if you wanted more for those subnets? Tough luck. You'd have to start over, right? So it's important to size your subnets properly, and I think you can see that assigning a subnet…

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