IP Addressing (IPv4 and IPv6)

Both IPv4 and IPv6 are Internet Protocol addressing standards supported by Mac OS X. They have common characteristics, as well as several differences that are described here.

IP Addressing

This provides a unique address to identify computers on the Internet.

It routes data when it moves from source to destination.

IP addresses are associated with the media access control (MAC) address of the client.

IPv4 (Internet Protocol version 4)

IPv4 supports up to four billion public addresses.

It defines the use of unique 32-bit addresses.

IPv4 addresses are formatted as four 8-bit fields (4 octets). For example, 192.168.1.2.

Classes are determined by the first octet:

• Class A: Large networks 1127

• Class B: Medium networks 128191

• Class C: Small networks 192223

• Class D: Multicast 224239

• Class E: Experimental 240255

The 127.0.0.1 address is used for loopback or localhost ID.

IPv6 (Internet Protocol version 6)

IPv6 is designed to increase the number of IP addresses, add features, and improve efficiencies of the IP protocol.

In 1995, Apple and Mentat announced that IPv6 was integrated with Apple Open Transport in Mac OS.

It uses CIDR (Classless Interdomain Routing).

It provides increased flexibility in address numbers.

IPv6 allows networks to be flexible in size so IP addresses aren't wasted.

Here are some features of IPv6:

• Does not rely on class size to determine network numbers

• Translates between IPv4 and IPv6 seamlessly

• Uses a 128-bit unique address

• Addresses are written in hexadecimal

• Uses 16-bit fields separated by colons rather than 8-bit fields separated by decimals

• Includes the MAC address of the active network interface

• Addresses in URLs are enclosed in brackets [ ]

IPv6 is built in to drivers for various networking interfaces. You can see protocols by using Terminal.

Enter

ifconfig -a

to show active network ports, addresses, and status.