What is CIDR

• Class inter-domain routing
• IP address scheme that improves the allocation of IP addresses.
• Helps in slowing growth of IP tables
• CIDR is based on variable-length subnet masking (VLSM)
• VLSM allows it to define prefixes of arbitrary length making it much more efficient.
• CIDR IP addresses are composed of two sets of numbers.
• The network address is written as a prefix
• The second part is a suffix that indicates how many bits are in the entire address
• ex: 192.255.255.255/12
• The lower suffix number represents a higher number of IP addresses. 5 IP addresses are always reserved for internal use.
• 10.0.0.0/8 --> 16M IP addresses, 10.0.0.0 to 10.255.255.255
• 10.0.0.0/16 --> 65K IP addresses, 10.0.0.0 to 10.0.255.255
• 10.0.0.0/24 --> 256 IP addresses, 10.0.0.0 to 10.0.0.255