IPv6 Networking FAQ

IPv6 code was merged into NetBSD in June 1999, and is part of NetBSD. IPv6 configuration is mostly the same as IPv4 configuration, so you may want to check the documentation for IPv4 networking.

The GENERIC kernel configuration enables IPv6 support by default for most of the architectures (ports). Userland code includes IPv6 support where possible, by default, so no rebuild of userland is necessary even if you switch between an IPv4-only kernel and an IPv4/v6 kernel.

Around 1992, the IETF became aware of a global shortage of IPv4 addresses, and technical obstacles in deploying new protocols due to limitations imposed by IPv4. An IPng (IP next generation) effort was started to solve these issues. The discussion is outlined in a bunch of RFCs, starting from RFC1550. After a large amount of discussion, around 1995, IPv6 (IP version 6) was picked as the final IPng proposal. The IPv6 base specification is specified in RFC2460.

In a single sentence, IPv6 is a re-engineering effort against IP technology. Key features are listed below:

There are number of good books available on IPv6. Be sure to check these if you are interested.

The network configuration is defined in a set of text configuration files. Note that you do not need to edit some of those if you are configuring a host (not a router), by using autoconfiguration.

In IPv6, routers and hosts are clearly separated. Nodes that forward packets for others are called routers. Nodes that do not are called hosts. Routers need to be configured manually. Routers will advertise information about subnet using rtadvd(8) daemon. Hosts usually have only one external network interface (some parts of this document assume this), and will be autoconfigured using the advertised subnet information.

There are two separate mechanisms defined for IPv6 host autoconfiguration. One is called stateless address autoconfiguration, and is specified in RFC4862. The other is called DHCPv6, and is specified in RFC3315. DHCPv6 is discussed in the IETF dhc working group. NetBSD currently implements RFC2462, the predecessor of RFC4862, and DHCPv6.

Stateless address configuration basically works as follows. We have two parties here: a host (which is to be autoconfigured) and a router (which emits necessary information to the host).

We call it stateless address autoconfiguration, since we do not need to manage state in the router side. It is a very simple, robust and effective autoconfiguration mechanism.

Note that we cannot autoconfigure routers. Routers really need to be configured manually.

First, you may want to get an IPv6 global address from upstream provider. If you have one, you'll need to perform the following steps.

If you have an IPv6 router on the network, all you have to do is as follows. After the reboot, the host will be autoconfigured by using Router Advertisements from the rtadvd(8) on the adjacent router.

If you do not have an IPv6 router on the network, you'll need to manually configure your system. See the following section for details.

Also, due to restrictions in the IPv6 specification, it is not recommended to autoconfigure a host with multiple external interfaces (like 2 ethernet interfaces). Please perform manual configuration in this case. See the following section for details.

One of the key value-adds of IPv6 is the ubiquitous availability of autoconfiguration. Since IPv6 addresses are 128 bits, there's a higher chance for mistakes in manual configuration. We strongly recommend that you avoid manual configuration whenever possible. For example:

Manual configuration should be reserved for hosts whose IPv6 address needs to remain static across hardware replacements (i.e. most often servers with application-specific firewall entries, or DNS servers). Note that it is normal for an IPv6 host to have more than one address, and that mixing dynamic addresses "for the host itself" and static addresses "for the application" is easy, and lets you automatically pick up router changes (but not prefix changes).

If you really need a manual configuration, read on.

If you need to configure a node manually, add manual configuration for network interfaces into rc.conf(5).

You will first need to declare the type of the node (host or router) by setting ip6mode as per below.

    ip6mode="router"        # forward packets for others
    ip6mode="host"          # do not forward packets for others

Then, add interface configuration into rc.conf(5), or other files sourced by /etc/rc.d/network such as /etc/ifconfig.xxN. You can have multiple lines in /etc/ifconfig.xxN, like:

    inet 10.1.1.1 netmask 0xffffff00
    inet6 2001:db8:1234::1 prefixlen 64 alias

Note "alias" at the end of the line. As there are multiple interface addresses with IPv6, the keyword is mandatory.

If your configuration is not covered by rc.conf(5), configuration can be added into /etc/netstart.local or /etc/rc.local. You will need to use the following programs:

A string hostname will be resolved to IPv6 numeric addresses by using /etc/hosts (hosts(5)), and/or DNS. This is much like the same as IPv4 case. yp(8) may be used, however, the author has no experience using yp(8) with IPv6 addresses.

Please note that the following addresses MUST NOT appear in the global DNS cloud:

It is not recommended to put these addresses onto DNS cloud:

For the NetBSD/KAME IPv6 code, putting the following address does not make sense due to lack of support:

There are couple of differences between IPv6 and IPv4 address allocation.

Depending on the ISP situation around you, you may be able to get native IPv6 connectivity (just like you do for IPv4), or you may be able to get tunnelled connectivity (IPv6 packets encapsulated into IPv4 packets). The section talks about the latter case.

You can hook your machine up to Hurricane Electric's IPv6 Tunnel Broker. You will need to talk with the nearest tunnel server to get your IPv6 address. They provide a web interface to update the IPv4 address of your tunnel if it changes.

If you do not have a fixed IPv4 global address (if you are using dialup ISP connection), don't panic. You can hook yourself up to Freenet6. They provide a web interface to hook up your home network whenever you reconnect to the Internet.

In both cases, you will need to set up an IPv6-over-IPv4 tunneling interface onto your router. Consult gif(4) for details. Hurricane Electric provides instructions for setting up tunnels on NetBSD.

The above configuration uses an RFC2893 IPv6-over-IPv4 configured tunnel. Note that RFC2893 packets will not be able to go through a NAT router (if your tunnel endpoint itself - a NetBSD box - is a NAT router, it should not be a problem).

See also:

Suppose you have obtained your address prefix, 2001:db8:1234::/48 from your upstream for your home network. You have two ethernet segments in your home, like below. Both myrouter A and myrouter B run IPv6-capable NetBSD. IPv4 addresses are assigned like below. You wish to connect to the upstream via IPv6-over-IPv4 tunnel, from myrouter A at x.x.0.1/24 to upstream router at y.y.y.10.

myrouter A
  | IPv4 x.x.0.1/24
  |
==+=== ethernet 0
  |
  | IPv4 x.x.0.2/24
myrouter B
  | IPv4 x.x.1.2/24
  |
==+=== ethernet 1

In some cases, your upstream may ask you to configure differently from the above scenario.

If you have more than one static global IPv4 address, you can use 6to4 mechanism (RFC3056) for your own /48 IPv6 prefix.

There are routers called "public 6to4 relay router" out there, which will behave as the other side of tunnel for you. You will need to configure one of your machines to behave as 6to4 gateway, which will encapsulate IPv6 packets into IPv4 and throw them to public 6to4 relay router (and vice versa). If your IPv4 address is x.y.z.u, your IPv6 prefix will be 2002:xxyy:zzuu::/48 (xx, yy, zz and uu is hexadecimal notation for x, y, z and u, respectively).

If your ISP gave you a private IPv4 address (like 10.x.x.x), unfortunately you cannot use this mechanism. The mechanism does not work across NAT devices.

Let us assume the following topology, and machine myrouter A has an IPv4 address x.y.z.u. IPv4 address for myrouter B does not matter.

myrouter A
  | IPv4 x.y.z.u
  |
==+=== ethernet 0
  |
myrouter B
  |
==+=== ethernet 1

See also:

To go to a totally IPv6 environment (without IPv4), you'd need to contact name servers using IPv6 cloud. It's easy: you just need to put IPv6 addresses into resolv.conf(5). If you would like to run an IPv6 transport ready DNS server, try running net/bind9. Example configuration would be like this:

    nameserver 2001:db8:0:1::f

We cannot connect directly from an IPv6-only client to an IPv4-only server, or vice versa. We need a device called a "translator" to do this.

NetBSD is shipped with the faithd(8) TCP relay translator, which can be used to enable an IPv6-only (or IPv4/v6) client to contact IPv4-only servers by using IPv6 TCP. By using it with net/totd DNS proxy server, you can install an IPv6-to-IPv4 translator environment, like this:

+--IPv6 only cloud------+
|			|
|IPv6 only		|			IPv4 only
|client	 == IPv6 ===> translator ----- IPv4 -->	servers
|	    tcp	      runs faithd(8)   tcp
|			|
+-----------------------+

For actual setup, please refer to the following documents.

See also:

If your organization has IPv4-only routers, IPv4 NAT routers, or other things that may become obstacles to direct IPv6 networking, you can overcome these hurdles by following ways. Pick the most suitable one for your network configuration:

Because IPv6 is still in its infancy, there are several non-standard items or specification holes. The KAME IPv6 implementation tries to address those.

Not about the specification, but there are some things worth mentioning:

If you have any questions, do not hesitate to ask on the tech-net mailing list. When you ask about your configuration, be VERY sure to attach a network diagram (ASCII art is fine) for your site. Without a network diagram, nobody can guess your network configuration.

See also:

The following programs in the base system are known to be IPv6-enabled: dig(1), finger(1), fstat(1), ftp(1), host(1), netstat(1), rlogin(1), rsh(1), systat(1), telnet(1), tftp(1), whois(1), faithd(8), fingerd(8), ftpd(8), ifconfig(8), inetd(8), lpd(8) (and friends), mld6query(8), named(8), ndp(8), ping6(8), pppd(8), rdate(8), rip6query(8), rlogind(8), route6d(8), rshd(8), sendmail(8), syslogd(8), tcpdchk(8) (and friends), telnetd(8), tftpd(8), traceroute6(8), trpt(8), X(7) (X server and libraries) .

RPC and NFS now support IPv6.

An increasing number of packages are also ready for IPv6.

If you want IPv6-ready third-party software, you may need to get an IPv6 patch for the software. There are collections of IPv6 patches on the net.