CIDR - Classless Inter-Domain Routing
CIDR stands for Classless Inter-Domain Routing. It's a method for allocating IP addresses and routing Internet Protocol packets.
In the notation of CIDR, the "/16" refers to the prefix size – which is the number of bits that remain constant for all devices within this network. In this case, "/16" means that the first 16 bits of the IP addresses in this network are constant, and the remaining bits can vary.
The IP address "111.31.0.0/16" represents an IP network with a range from 111.31.0.0 to 111.31.255.255. Here's how:
- An IP address is 32 bits long.
- With a "/16" subnet, the first 16 bits (111.31.0.0) are the network part, while the last 16 bits are used for host addresses within the network.
- So, you can have 2^16 (65,536) IP addresses in this range, from 111.31.0.1 to 111.31.255.254. The addresses 111.31.0.0 and 111.31.255.255 are typically reserved for network and broadcast addresses respectively, so they are not used for host addresses.
In the context of an AWS VPC, this range of IP addresses (111.31.0.0/16) would be the range of private IP addresses that can be assigned to instances within the VPC.
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