CIDR = A way to describe a range of IP addresses

Think of it like describing a neighborhood of houses instead of listing every single house address.

CIDR Has Two Parts

Example: 192.168.0.0/24

1. Base IP: 192.168.0.0

• The starting address

2. Subnet Mask: /24

• How many addresses are in this range

Understanding the Subnet Mask - The Easy Way to remember

The number after the slash (/) tells you how many IPs you get:

Quick Memory Guide (Octets):

An IP has 4 parts (octets): 192.168.0.0

• 1st octet: 192
• 2nd octet: 168
• 3rd octet: 0
• 4th octet: 0

The /number tells you which parts are LOCKED:

• /32 = All 4 octets locked = Only 1 IP (exact address)
  • Example: 134.56.78.123/32 = Just 134.56.78.123
• /24 = First 3 octets locked, last can change = 256 IPs
  • Example: 192.168.0.0/24 = 192.168.0.0 to 192.168.0.255