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IPv4

  • 32 bits
  • Written as four decimal numbers called octets
    • Octet --> 8 bits
    • Each octet can be any number from 0 to 255
  • Divided into two parts
    • Network ID
    • Host ID

Private IPs

  • A company can use private IPs on its private networks
  • IEEE recommends the following:
    • 10.0.0.0 through 10.255.255.255.255
    • 172.16.0.0 through 172.31.255.255
    • 192.168.0.0 through 192.168.255.255

Classes

  • Dividing line between network and host portions is determined by numerical range IP address falls in
  • Class A, B, and C are available for use on the internet
    • Public IP addresses
  • Classes D and E are not available for general use:
    • Class D begins with octets 224-239 --> use for multicasting
    • Class E begins with octets 240-254 --> used for research
Class Network octets Octet Range Default Mask Approx. number of possible networks Approx. number of IP aπddresses in each network
A 1.x.y.z to 126.x.y.z 1-126 255.0.0.0 126 16 million
B 128.0.x.y to 191.255.x.y 128-191 255.255.0.0 16,000 65,000
C 192.0.0.x to 223.255.255.x 192-223 255.255.255.0 2 million 254

Reserved IPs

IP Address(es) Function
255.255.255.255 Used to broadcast messages by TCP/IP background processes. Message is read by every node on the network.
0.0.0.0 Unassigned
127.0.0.1 through 127.255.255.254 Uses for research or your own computer (loopback address)
169.254.0.1 through 169.254.255.254 Used to create APIPA address when a computer configured for DHCP first connects to the network and is unable to lease an IPv4 address from DHCP server.

Subnet Calculations

  • Subnetting
    • Alters the rules of classful IPv4 addressing
    • Called classless addressing
  • Borrow bits that would represent host information in classful addressing and use those bits to represent network information
    • Increase number of bits available for the network ID
    • Reduce number of bits available for identifying hosts
      • Reduce the number of usable host addresses in each network

Computer Science Networking IP Address

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