IP Adresses

Each host on the Internet has a unique IP address. IPv4 addresses are 32 bits (4 octets) in length and are usually displayed in dotted decimal format (i.e. 206.86.196.1). Displayed below is how the IP address "206.86.196.1" is written in binary format.

        (8 bits) + (8 bits) + (8 bits) + (8 bits)  = 32
        11001110   01010110   11000100   00000001
          206         86        196          1  
           |
            -----------------
                             |
                             V

        1     1     0     0    1     1     1    0
       128   64    32    16    8     4     2    1
      --------------------------------------------
       128 + 64              + 8   + 4   + 2       = 206

IP Address Classes

• Network Portion = 8 bits (1st bit = 0)
• Host Portion = 24 bits
• Address Range = 1.0.0.0 to 126.0.0.0

• Network Portion = 16 bits (1st two bits = 1 & 0)
• Host Portion = 16 bits
• Address Range = 128.0.0.0 to 191.255.0.0

• Network Portion = 24 bits (1st three bits = 1 , 1 & 0)
• Host Portion = 8 bits
• Address Range = 192.0.1.0 to 223.255.255.0

Quick Notes:

• 127.0.0.0 is reserved for loopback and is used for inter-process communication on the local host.
• Reserved IP addresses for private use.
  • 10.0.0.0 -> 10.255.255.255
  • 172.16.0.0 -> 172.31.255.255
  • 192.168.0.0 -> 192.168.255.255
  • Reference RFC 1918
• Class D; 224.0.0.0 -> 239.255.255.255 is reserved for multicast addresses.