IPv6 (also known as IPng “IP next generation”) is the new version of the well known IP protocol (also known as IPv4). Like the other current *BSD systems, FreeBSD includes the KAME IPv6 reference implementation. So your FreeBSD system comes with all you will need to experiment with IPv6. This section focuses on getting IPv6 configured and running.
In the early 1990s, people became aware of the rapidly diminishing address space of IPv4. Given the expansion rate of the Internet there were two major concerns:
Running out of addresses. Today this is not so much of
a concern any more, since RFC1918 private address space
(10.0.0.0/8,
172.16.0.0/12, and
192.168.0.0/16) and Network
Address Translation (NAT) are being
employed.
Router table entries were getting too large. This is still a concern today.
IPv6 deals with these and many other issues:
128 bit address space. In other words theoretically there are 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses available. This means there are approximately 6.67 * 10^27 IPv6 addresses per square meter on our planet.
Routers will only store network aggregation addresses in their routing tables thus reducing the average space of a routing table to 8192 entries.
There are also lots of other useful features of IPv6 such as:
Address autoconfiguration (RFC2462)
Anycast addresses (“one-out-of many”)
Mandatory multicast addresses
IPsec (IP security)
Simplified header structure
Mobile IP
IPv6-to-IPv4 transition mechanisms
For more information see:
There are different types of IPv6 addresses: Unicast, Anycast and Multicast.
Unicast addresses are the well known addresses. A packet sent to a unicast address arrives exactly at the interface belonging to the address.
Anycast addresses are syntactically indistinguishable from unicast addresses but they address a group of interfaces. The packet destined for an anycast address will arrive at the nearest (in router metric) interface. Anycast addresses may only be used by routers.
Multicast addresses identify a group of interfaces. A packet destined for a multicast address will arrive at all interfaces belonging to the multicast group.
The IPv4 broadcast address (usually
xxx.xxx.xxx.255) is expressed
by multicast addresses in IPv6.
| IPv6 address | Prefixlength (Bits) | Description | Notes |
|---|---|---|---|
:: | 128 bits | unspecified | cf. 0.0.0.0 in
IPv4 |
::1 | 128 bits | loopback address | cf. 127.0.0.1 in
IPv4 |
::00:xx:xx:xx:xx | 96 bits | embedded IPv4 | The lower 32 bits are the IPv4 address. Also called “IPv4 compatible IPv6 address” |
::ff:xx:xx:xx:xx | 96 bits | IPv4 mapped IPv6 address | The lower 32 bits are the IPv4 address. For hosts which do not support IPv6. |
fe80:: - feb:: | 10 bits | link-local | cf. loopback address in IPv4 |
fec0:: - fef:: | 10 bits | site-local | |
ff:: | 8 bits | multicast | |
001 (base
2) | 3 bits | global unicast | All global unicast addresses are assigned from this pool. The first 3 bits are “001”. |
The canonical form is represented as:
x:x:x:x:x:x:x:x, each
“x” being a 16 Bit hex value. For example
FEBC:A574:382B:23C1:AA49:4592:4EFE:9982
Often an address will have long substrings of all zeros
therefore one such substring per address can be abbreviated by
“::”. Also up to three leading “0”s
per hexquad can be omitted. For example
fe80::1 corresponds to the
canonical form fe80:0000:0000:0000:0000:0000:0000:0001.
A third form is to write the last 32 Bit part in the
well known (decimal) IPv4 style with dots “.”
as separators. For example
2002::10.0.0.1
corresponds to the (hexadecimal) canonical representation
2002:0000:0000:0000:0000:0000:0a00:0001
which in turn is equivalent to writing
2002::a00:1.
By now the reader should be able to understand the following:
# ifconfigfe80::200:21ff:fe03:8e1%rl0
is an auto configured link-local address. It is generated
from the MAC address as part of the auto configuration.
For further information on the structure of IPv6 addresses see RFC3513.
Currently there are four ways to connect to other IPv6 hosts and networks:
There used to be two types of DNS records for IPv6. The IETF has declared A6 records obsolete. AAAA records are the standard now.
Using AAAA records is straightforward. Assign your hostname to the new IPv6 address you just received by adding:
To your primary zone DNS file. In case you do not serve
your own DNS zones ask your
DNS provider. Current versions of
bind (version 8.3 and 9) and
dns/djbdns (with the IPv6
patch) support AAAA records.
These settings will help you configure a machine that
will be on your LAN and act as a client, not a router. To
have rtsol(8) autoconfigure your interface on boot on
FreeBSD 9.x and later,
add:
to rc.conf.
For FreeBSD 8.x and
earlier, add:
To statically assign an IP address such as 2001:471:1f11:251:290:27ff:fee0:2093,
to your fxp0 interface, add the
following for
FreeBSD 9.x:
64"Be sure to change prefixlen
64 to the appropriate value for the subnet
within which the computer is networked.
For FreeBSD 8x and earlier,
add:
To assign a default router of
2001:471:1f11:251::1 add the
following to /etc/rc.conf:
This will help you take the directions that your tunnel
provider has given you and convert it into settings that
will persist through reboots. To restore your tunnel on
startup use something like the following in
/etc/rc.conf:
List the Generic Tunneling interfaces that will be
configured, for example
gif0:
To configure the interface with a local endpoint of
MY_IPv4_ADDR to a remote endpoint
of REMOTE_IPv4_ADDR:
MY_IPv4_ADDR REMOTE_IPv4_ADDR"To apply the IPv6 address you have been assigned for use
as your IPv6 tunnel endpoint, add the following for
FreeBSD 9.x and later:
MY_ASSIGNED_IPv6_TUNNEL_ENDPOINT_ADDR"For FreeBSD 8.x and
earlier, add:
MY_ASSIGNED_IPv6_TUNNEL_ENDPOINT_ADDR"Then all you have to do is set the default route for IPv6. This is the other side of the IPv6 tunnel:
MY_IPv6_REMOTE_TUNNEL_ENDPOINT_ADDR"This section will help you setup rtadvd(8) to advertise the IPv6 default route.
To enable rtadvd(8) you will need the following in
your /etc/rc.conf:
It is important that you specify the interface on which to
do IPv6 router solicitation. For example to tell
rtadvd(8) to use fxp0:
Now we must create the configuration file,
/etc/rtadvd.conf. Here is an
example:
Replace fxp0 with the interface
you are going to be using.
Next, replace
2001:471:1f11:246:: with the
prefix of your allocation.
If you are dedicated a /64
subnet you will not need to change anything else. Otherwise,
you will need to change the prefixlen# to
the correct value.
This, and other documents, can be downloaded from ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/
For questions about FreeBSD, read the
documentation before
contacting <questions@FreeBSD.org>.
For questions about this documentation, e-mail <doc@FreeBSD.org>.