IPv6, also known as IPng “IP next generation”, is the new version of the well known IP protocol, also known as IPv4. FreeBSD includes the KAME IPv6 reference implementation. FreeBSD comes with everything needed to use 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. For years the use of
RFC1918 private address space
(10.0.0.0/8,
172.16.0.0/12, and
192.168.0.0/16) and NAT
has slowed down the exhaustion. Even though, there are
very few remaining IPv4 addresses. The Internet
Assigned Numbers Authority (IANA) has
issued the last of the available major blocks to the
Regional Registries. Once each Regional Registry runs
out, there will be no more available and switching to
IPv6 will be critical.
Every block of IPv4 addresses allocated required routing information to be exchanged between many routers on the Internet, and these routing tables were getting too large to allow efficient routing.
IPv6 deals with these and many other issues by providing the following:
128 bit address space which allows for 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses. This means there are approximately 6.67 * 10^27 IPv6 addresses per square meter on the planet.
Routers only store network aggregation addresses in their routing tables, thus reducing the average space of a routing table to 8192 entries.
There are many other useful features of IPv6:
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 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 | Equivalent to 0.0.0.0 in
IPv4. |
::1 | 128 bits | loopback address | Equivalent to 127.0.0.1 in
IPv4. |
::00:xx:xx:xx:xx | 96 bits | embedded IPv4 | The lower 32 bits are the compatible IPv4 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 | Equivalent to the 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, with 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.
One such substring per address can be abbreviated by
“::”. Also, up to three leading
“0”s per hex quad 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 2002::a00:1.
Here is a sample entry from ifconfig(8):
# 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:
Contact an Internet Service Provider to see if they offer IPv6.
SixXS offers tunnels with end-points all around the globe.
Hurricane Electric offers tunnels with end-points all around the globe.
Tunnel via 6-to-4 as described in RFC3068.
Use the
net/freenet6 port
for a dial-up connection.
To automatically configure a machine on a
LAN which acts as a client, not a
router, two items are required. First to enable the
em0 to receive the router
solicitation messages, add this line to
rc.conf:
em0_ipv6="inet6 accept_rtadv"Secondly, the router solicitation daemon, rtsol(8),
should be enabled by adding the following to
rc.conf:
For FreeBSD 8.x,
add:
To statically assign the IPv6
address, 2001:db8:4672:6565:2026:5043:2d42:5344,
to fxp0, add the following for
FreeBSD 9.x:
fxp0_ipv6="inet6 2001:db8:4672:6565:2026:5043:2d42:5344 prefixlen 64"Be sure to change prefixlen
64 to the appropriate value for the
subnet.
For FreeBSD 8.x,
add:
fxp0="2001:db8:4672:6565:2026:5043:2d42:5344"To assign a default router of 2001:db8:4672:6565::1, add the
following to /etc/rc.conf:
This section demonstrates how to take the directions
from a tunnel provider and convert it into settings that
will persist through reboots. To restore the tunnel on
startup, add the following lines to
/etc/rc.conf.
The first entry lists the generic tunneling interfaces
to be configured. This example configures one interface,
gif:0
0"To configure that 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 that has
been assigned for use as the IPv6 tunnel
endpoint, add the following line for
FreeBSD 9.x and later:
MY_ASSIGNED_IPv6_TUNNEL_ENDPOINT_ADDR"For FreeBSD 8.x,
add:
MY_ASSIGNED_IPv6_TUNNEL_ENDPOINT_ADDR"Then, set the default route for IPv6. This is the other side of the IPv6 tunnel:
MY_IPv6_REMOTE_TUNNEL_ENDPOINT_ADDR"This section demonstrates how to setup rtadvd(8) to advertise the IPv6 default route.
To enable rtadvd(8), add the following to
/etc/rc.conf:
It is important to specify the interface on which to
do IPv6 router solicitation. For example,
to tell rtadvd(8) to use
fxp0:
Next, create the configuration file,
/etc/rtadvd.conf as seen in this
example:
Replace fxp0 with the interface
to be used and 2001:471:1f11:246:: with the
prefix of the allocation.
For a dedicated /64
subnet, nothing else needs to be changed. Otherwise, change
the prefixlen# to the correct value.
When IPv6 is enabled on a server, there may be a need to enable IPv4 mapped IPv6 address communication. This compatibility option allows for IPv4 addresses to be represented as IPv6 addresses. Permitting IPv6 applications to communicate with IPv4 and vice versa may be a security issue.
This option may not be required in most cases and is
available only for compatibility. This option will allow
IPv6-only applications to work with
IPv4 in a dual stack environment. This
is most useful for third party applications which may not
support an IPv6-only environment. To
enable this feature,
add the following to /etc/rc.conf:
Reviewing the information in RFC 3493, section 3.6 and 3.7 as well as RFC 4038 section 4.2 may be useful to some adminstrators.
Currently IPv6 support for many applications and services is very good, though for some software it still needs work. For authoritative information about the support of IPv6, please consult the Official Documentation for the software in question.
Web, DNS and Mail applications and servers have the best support for IPv6 because they are the most common use case. Other applications may have varying degrees of IPv6 support.
All FreeBSD documents are available for download at http://ftp.FreeBSD.org/pub/FreeBSD/doc/
Questions that are not answered by the
documentation may be
sent to <freebsd-questions@FreeBSD.org>.
Send questions about this document to <freebsd-doc@FreeBSD.org>.