🖥️cidr

➡️This is a command-line reference manual for commands and command combinations that you don’t use often enough to remember it. This cheatsheet explains the cidr command with important options and switches using examples.

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# cidr - Classless Inter-Domain Routing

# Before CIDR and Variable Length Subnet Masks, IP addresses had fixed subnet masks
# Class C had a 24 bit prefix (/24), Class B had a 16 bit prefix (/16), and Class A had an 8 bit prefix (/8)

# Note: The prefix determines how many addresses are covered by the CIDR address. The prefix is the number of bits reserved for the network portion of the address

# An IP address consists of a host and a network portion
# The 32 bit string below represents a /16 network since 16 bits are dedicated to the network portion of the address
# Network bits / Host bits
11111111 11111111 / 00000000 00000000

# As an example, if we were to make a subnet with only 2 addresses on the 3.3.3.0 network, the network prefix would be /31
# If we view this in binary it would look like:
00000011.00000011.00000011.00000000 (3.3.3.0)

# The subnet mask then becomes
11111111.11111111.11111111.11111110 (/31)

# In the subnet mask above, only one bit is available for modification, so the only two available IP addresses would be: 
3.3.3.0 and 3.3.3.1

# 3.3.3.2 would represent the start of another subnet 
 
# If we changed the prefix to /30, the new IP address range would be
3.3.3.0 - 3.3.3.3

Cheatsheets are an excellent complement to other information sources like Linux man-pages, Linux help, or How-To’s and tutorials, as they provide compact and easily accessible information. While man-pages and detailed tutorials often contain comprehensive explanations and extensive guides, cheatsheets summarize the most important options forthe command cidr in a clear format. This allows users to quickly access the needed information for cidr without having to sift through lengthy texts. Especially in stressful situations or for recurring tasks, cheatsheets for cidr are a valuable resource to work efficiently and purposefully.

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