IPv6: Quick start for administrators

May 26th, 2013 by William Smith

Networking support folks have been buzzing about IPv6 since it was first formally introduced in December 1998. This is the IP addressing system to augment the current IPv4 system in use since the 1970s. It promises a much bigger address space for the world’s increasing number of Internet-connected devices.

Addresses will go from looking like this (IPv4):

to looking something like this (IPv6):


We’re experimenting with IPv6 in our offices, so I thought I’d compile a short list of things administrators may find useful to know.

1) An IP address for every atom in your body

The purpose of IPv6 is to provide more assignable addresses to devices on the Internet. The world is running out of IPv4 addresses due to mobile devices, permanently connected devices and inefficient use of the addresses IPv4 offers. IPv6 offers so many addresses that it could offer an IP address for every atom in the human body.

IPv4:  4,294,967,296

Body:  7,000,000,000,000,000,000,000,000,000

IPv6:  430,282,366,920,938,463,463,374,607,431,678,211,456

2) Format

The basic IPv6 address format differs from IPv4 in three ways:


IPv4 addresses use decimal numbers for each digit whereas IPv6 addresses use hexadecimal numbers.

IPv4:  0 1 2 3 4 5 6 7 8 9 (10 possible digits)

IPv6:  0 1 2 3 4 5 6 7 8 9 a b c d e f (16 possible digits)


IPv4 addresses use four octets, each ranging from 000 to 255. IPv6 addresses use eight hextets, each ranging from 0000 to ffff.


IPv6:  0000:0000:0000:0000:0000:0000:0000:0000


IPv4 octets are separated by periods whereas IPv6 hextets are separated by colons.


IPv6:  0000:0000:0000:0000:0000:0000:0000:0000

3) Abbreviating

These IPv6 addresses are huge! Do we really need to write out the whole thing?

Nope. Similar to IPv4, IPv6 allows omitting leading zeros in a hextet. Additionally, an abbreviated IPv6 address replaces consecutive zeros with a double colon “::” but only once per address. It also allows substituting one zero for a group of zeros in a hextet.

IPv4: is the same as

IPv6:  fe80:0db8:85a3:0042:1000:0000:0370:7334

is the same as




4) Ping6

To ping IPv4 addresses use the ping command. To ping IPv6 addresses using the ping6 command.

IPv4: ping

IPv6: ping6 fe80:db8:85a3:42:1::370:7334

5) Self-assigned IP addresses

When two devices are on the same network but aren’t assigned IP addresses from a DHCP server, they can assign themselves IP addresses to communicate with each other. This is called Automatic Private IP Addressing (APIPA) or Link-local addressing.

Both IPv4 and IPv6 will self-assign their IP addresses within a reserved range of addresses just for this purpose.

IPv4: -


fe80:: - febf:ffff:ffff:ffff:ffff:ffff:ffff:ffff

A computer may assign itself an IPv6 address using the last six characters of its MAC address:

MAC: 00:23:6c:7c:f6:b9

IPv6: fe80:5::223:6cff:fe7c:f6b9

6) Tunneling

Not everyone’s Internet Service Provider is offering IPv6 addresses just yet. But IPv6 can be “tunneled” over IPv4 networks to connect with other IPv6 networks. Tunneling doesn’t require much configuration other than to tell your IPv6-capable router to do the tunneling.

Tunneled IPv6 addresses will begin with 2002. Compare tunneled addresses with dynamic and self-assigned addresses:

IPv6 dynamic address: 2607:f0d0:1002:51::4

IPv6 tunneled address:


IPv6 self-assigned address:


7) Loopback address

The loopback address refers to the computer itself. For example, to test a website running on a local computer use the loopback address as the IP address in the browser.

The IPv6 loopback address is simply “1″.


IPv6: ::1

To ping the local computer use:

ping6 ::1

8) Parts of an IPv6 address

Similar to an IPv4 address, an IPv6 address is made of parts. The first part of an IPv4 address denotes the network and the second denotes the  host’s unique number. A separate subnet mask tells the computer how to distinguish between the network number of the IP address and the host number.

IPv4 address:

Network: 192.168.0


Host: 10

Unlike IPv4, however, an IPv6 address will include its subnet information within itself instead of specifying it separately. The fourth hextet is always the subnet ID.

IPv6 address:fe80:db8:85a3:42:1::370:7334




9) Test IPv6 readiness

Most home routers today, including Apple’s Airport Extreme, support IPv6 networking. Not all Internet Service Providers, though, offer IPv6 to their customers yet. Use these sites to test IPv6 readiness.

Using Comcast? The top of this page will show the customer’s IPv6 address if it has one:


Test IPv6 connectivity:


A slew of IPv6 Internet tools:


10) Use IPv6 DNS servers

OpenDNS.com offers public DNS servers as alternatives to an ISP’s DNS servers, which may be slower to respond or less reliable.

  • 2620:0:ccc::2
  • 2620:0:ccd::2

Google offers public DNS servers supporting IPv6 as well.

  • 2001:4860:4860::8888
  • 2001:4860:4860::8844

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