Networking Refresher: IP, CIDR, Subnetting

Building resilient and secure infrastructures and workloads requires a fundamental understanding of networking. In the context of the cloud, we don’t have to manage our own physical hardware, but the task of configuring the virtual resources to meet our requirements and operate effectively lies with us.

Keeping this in perspective, let's familiarize ourselves with the basics of the Internet Protocol used by AWS services to communicate with each other.

Internet Protocol

Internet Protocol outlines the set of rules for addressing and routing data on the internet. It enables communication between two host machines over a network. Every host machine or device on the internet is assigned a unique identifier, namely an IP address. The Internet Protocol delivers the packets over the network using these unique identifiers. Once delivered, the transport layer protocols take over further processing the packets and handing them over to the respective applications.

The Internet Protocol addresses come in two flavors:

• IPv4

• IPv6

IPv4

Internet Protocol version 4, or IPv4, is a 32-bit addressing scheme where each IP address is denoted by four octets separated by dots, for example: 10.0.0.0. Each octet in the IP address represents 8 bits, which means that the value can range from 0 to 255. Similarly, since IPv4 supports 32 bits, we can have $2^{32}$or approximately 4 billion uniquely identifiable IP addresses, which in our day and age are insufficient.

IPv6

To deal with the limited number of addresses in IPv4, Internet Protocol version 6 or IPv6 supports 128-bit addresses, which are represented by a hexadecimal notation. Each IPv6 address has eight 16-bit sections, each separated by a colon, for example: d14c:1368:3e4a:0c9f:fcf5:460c:e7dd:3205. With 128 bits, we can uniquely identify $2^{128}$ devices, which is $2 ^ {96}$ ...