From Wikiversity

Contents 1 IPv4 Addressing 1.1 Subnet Masks 1.2 Dotted Decimal Notation 1.3 CIDR Notation 2 Classes 2.1 Loopback Addresses 2.2 Private Addresses 2.3 Subnetting

[edit] IPv4 Addressing

IPv4 Addressing refers to an address that conforms to the Version 4 standard of the Internet Protocol (IP). These addresses are assigned to computers to identify them on an IP Network. IPv4 addresses are 32-bits long, with 4 octets of 8 bits each. While IP Addresses are binary numbers, IP Addresses are usually written in what is called a dotted decimal notation so that they are human readable. Dotted Decimal notation is accomplished by converting the binary values of each octet to its decimal number equivilent and placing a decimal point between each octet (i.e. 159.203.155.100).

[edit] Subnet Masks

[edit] Dotted Decimal Notation

Like the IPv4 Address itself, Subnet Masks are sometimes represented in dotted decimal notation.

[edit] CIDR Notation

Classless Interdomain Routing (CIDR) Notation refers to using a two to three character representation of a subnet mask. CIDR is written as a slash (\) and then a number that represents the number of bits used in the subnet mask. For example, if a subnet mask in binary format is 11111111111111110000000000000000, there are 16 total on bits, therefore the CIDR Notation for this mask would be \16.

[edit] Classes

• Class A
  • Contains the IPv4 Addresses 0.0.0.0-127.255.255.255. Default subnet mask is 255.0.0.0.
• Class B
  • Contains the IPv4 Addresses 128.0.0.0-191.255.255.255. Default subnet mask is 255.255.0.0.
• Class C
  • Contains the IPv4 Addresses 192.0.0.0-223.255.255.255. Default subnet mask is 255.255.255.0.
• Class D
  • Contains the IPv4 Addresses 224.0.0.0-239.255.255.255. This address is for multicasting.
• Class E
  • Contains the IPv4 Addresses 240.0.0.0-255.255.255.255. These addresses are reserved by the Internet Assigned Numbers Authority (IANA) and should not be used on IP Networks.

[edit] Loopback Addresses

The 127.0.0.0/8 network is a part of the Class A classification, but it is designated for loopback addressing and cannot be assigned to a network. The loopback subnet is not routable on the internet.

[edit] Private Addresses

There are 3 IPv4 address ranges that are considered private addresses, and these ranges are:

• Class A: 10.0.0.0/8
• Class B: 172.16.0.0-172.32.0.0/16
• Class C: 192.168.0.0/24

These addresses are not routable on the internet, meaning that in order for computers that are assigned a private address to communicate with the internet, a Network Address Translation (NAT) service must be put in place between the privately addressed computer and the internet.

[edit] Subnetting

Subnetting describes the process of dividing IP Addresses into logical subnetworks.