For all those who don’t like to remember the details I have included my quick reference to IPv4. It’s not full fledged but can offer some pointing in the right direction. IPv4 is the fourth iteration of the Internet Protocol (IP) and is the most widely deployed. If you want some ugly history details you can always refer to IETF RFC (791). Otherwise just know IPv4 is a data oriented protocol to be used on packet switched internet works such as ethernet.
The following shows Version 4 IP addressing consisting of 32-bit binary number of four octets (dotted decimal notation)
Classful Addresses
Class A (24 Bit) 1-126.x.x.x Class B (20 Bit) 128-191.x.x.x Class C (16 Bit) 192-223.x.x.x Class D Multicast 224-239.x.x.x Internal Loopback 127 |
Private IP Address Ranges
Class A (24 Bit) 10.0.0.0-10.255.255.255 CIDR Mask /8 Decimal Mask 255.0.0.0 Class B (20 Bit) 172.16.0.0-172.31.255.255 CIDR Mask /12 Decimal Mask 255.240.0.0 Class C (16 Bit) 192.168.0.0-192.168.255.255 CIDR Mask /16 Decimal Mask 255.255.0.0 |
/24 IP Bit Mask
Dotted Decimal Mask: 255.255.255.0 Effective Hosts: 254 Effective Subnets: 1 Usable IP's: 254 |
/25 IP Bit Mask
Dotted Decimal Mask: 255.255.255.128 Effective Hosts: 252 Effective Subnets: 2 Usable IP's: 126 |
/26 IP Bit Mask
Dotted Decimal Mask: 255.255.255.192 Effective Hosts: 248 Effective Subnets: 4 Usable IP's: 62 |
/27 IP Bit Mask
Dotted Decimal Mask: 255.255.255.224 Effective Hosts: 240 Effective Subnets: 8 Usable IP's: 30 |
/28 IP Bit Mask
Dotted Decimal Mask: 255.255.255.240 Effective Hosts: 224 Effective Subnets: 16 Usable IP's: 14 |
/29 IP Bit Mask
Dotted Decimal Mask: 255.255.255.248 Effective Hosts: 192 Effective Subnets: 32 Usable IP's: 6 |
/30 IP Bit Mask
Dotted Decimal Mask: 255.255.255.252 Effective Hosts: 128 Effective Subnets: 64 Usable IP's: 2 |