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CIDR

CIDR = Classless Inter-Domain Routing

It defines how many IP addresses are in a network (or subnet) using a “slash” notation.

Example: 192.168.10.0/24

• Network address: 192.168.10.0
• Prefix Length: /24 means this network will have 256 total IPs

Number of IPs = 2^(32 - prefix)

But AWS and most networks reserve 5 IPs in each subnet:

• 1 for network address
• 1 for broadcast address
• 3 reserved by AWS (for internal routing, DNS, etc.)

/24 subnet gives 251 usable IPs

192.168.10.0 = 11000000.10101000.00001010.00000000

Last 8 digits goes like this

00000100 
00000101
00000101
00000110
.....
.....
11111111

#cidr #ipv4 #subnetVer 0.3.6