IPv4/IPv6 transition technologies

See also: NAT64 for IPv6-only networks, NAT66 and IPv6 masquerading, IPv6 NAT and NPT

Transition technologies can be installed using the following packages:

• IPv6-in-IPv4 tunnels: 6rd, 6to4, 6in4.
• IPv4-in-IPv6 tunnels: ds-lite.

See also: Setting up an IPv6 Tunnel with LuCI, IPv6 with Hurricane Electric

6in4 tunnels are usually provided by external tunnel providers like HE.net.

The package 6in4 must be installed to use this protocol.

6in4 requires you to have a public IPv4 address, clients behind CGNAT are not supported.

The example below illustrates a static tunnel configuration for the Hurricane Electric (he.net) broker. option ipaddr specifies the local IPv4 address, peeraddr is the broker IPv4 address and ip6addr the local IPv6 address routed via the tunnel.

# /etc/config/network
config interface 'wan6'
        option proto        '6in4'
        option ipaddr       '178.24.115.19'
        option peeraddr     '216.66.80.30'
        option ip6addr      '2001:0DB8:1f0a:1359::2/64'

The example below illustrates a dynamic tunnel configuration for the Hurricane Electric (he.net) broker with enabled IP update. The local IPv4 address is determined automatically. The options tunnelid, username and updatekey are provided for IP update.

# /etc/config/network
config interface 'wan6'
        option proto     '6in4'
        option mtu       '1424'                      # the IPv6 tunnel MTU (optional)
        option peeraddr  '216.66.80.30'              # the IPv4 tunnel endpoint at the tunnel provider
        option ip6addr   '2001:0db8:1f0a:1359::2/64' # the IPv6 tunnel address
        option ip6prefix '2001:db8:1234::/48'        # Your routed prefix (required)
        # configuration options below are only valid for HE.net tunnels, ignore them for other tunnel providers.
        option tunnelid  '12345'                     # HE.net tunnel id
        option username  'username'                  # HE.net username used to login into tunnelbroker, not the User ID shown after login in.
        option updatekey 'updatekey'                 # HE.net updatekey instead of password, default for new tunnels

See below for advanced configuration options.

In a typical tunnel configuration (e.g. HE.net) you get two different ipv6 addresses/prefixes from the tunnel provider:

• ip6addr: The tunnel endpoint address is like '2001:DB8:2222:EFGH::2/64'. This ...::2 address is only used for the tunnel interface endpoint. It is not a routable address and it can't be used for anything else than connecting to the other end of the tunnel, typically ...::1 .
• ip6prefix: The tunnel provider gives you also a routable prefix, typically either /48 or /64, for example '2001:DB8:1112::/48' or '2001:DB8:1234:ABCD::/64'. Your LAN clients will get addresses from that prefix. Using a wider prefix helps delegate IPv6 to several downstream networks.

Some users may require to add extra firewall rules to allow 6in4 traffic to always reach their tunnel endpoint. The package iptables-mod-ipopt must be installed for length matching.

# /etc/config/firewall
config rule
        option name      'Allow-protocol-41'
        option src       'wan'
        option proto     '41'
        option target    'ACCEPT'
 
config rule
        option name      'Allow-protocol-59'
        option src       'wan'
        option proto     '59'
        option target    'ACCEPT'
        option extra     '-m length --length 40'

Provide default route to override sourcefilter.

# /etc/config/network
config route6
        option interface 'wan6'
        option target    '::/0'

This protocol type does not need the device option set in the interface section. The interface name is derived from the section name, e.g. config interface sixbone would result in an interface named 6in4-sixbone.

Although ip6prefix isn't required, sourcefilter is enabled by default and prevents forwarding of packets unless ip6prefix is specified.

6rd is a tunnel mechanism based on 6to4. Unlike other tunneling mechanisms, 6rd is usually provided by the ISP itself.

The package 6rd must be installed to use this protocol.

The configuration of 6rd is usually auto-detected and manual configuration is not needed, simply installing the 6rd package (and rebooting) is usually enough.

To automatically configure 6rd from dhcp you need to create an interface with option auto 0 and put its name as the 'iface6rd' parameter. In addition you also need to add its name to a suitable firewall zone in /etc/config/firewall.

# /etc/config/network
config interface 'wan6'
        option proto '6rd'
        option peeraddr '77.174.0.2'
        option ip6prefix '2001:838:ad00::'
        option ip6prefixlen '40'
        option ip4prefixlen '16'

To debug 6rd via DHCP, enable DHCP client logging, reboot the router, and check the logs:

# logread -e ip6rd
ip6rd=16 40 2001:0838:ad00:0000:0000:0000:0000:0000 77.174.0.2

If this line isn't present, you need to obtain the correct values for peeraddr, ip6prefix, ip6prefixlen and ip4prefixlen from your ISP. The above ip6rd or the obtained values can be used to hardcode the 6rd tunnel. Remove or comment out the iface6rd line in the wan section.

If you choose a name for your tunnel-interface different from wan6, be sure to add that network to the wan firewall-zone.

Below configuration options are only needed for hardcoding the 6rd tunnel.

This protocol type does not need the device option set in the interface section. The interface name is derived from the section name, e.g. config interface wan6 would result in an interface named 6rd-wan6.

Some ISP's give you the number of bytes you should use from your WAN IP to calculate your IPv6 address. ip4prefixlen expects the prefix bytes of your WAN IP to calculate the IPv6 address. So if your ISP gives you 14 bytes to calculate, enter 18 (32 - 14).

This is another transitional mechanism for IPv6 used by some ISPs, it relies on a L2TPv2 tunnel.

The package xl2tpd must be installed to use this protocol. It will handle the L2TP tunnel and PPP session.

The high-level description of the tunneling is the following:

1. An L2TP tunnel is created, encapsulated in UDP packets over IPv4.
2. A PPP session is established inside the tunnel.
3. IPv6CP (see RFC 5072) is used to negotiate link-local IPv6 addresses.
4. An IPv6 prefix is obtained thanks to DHCPv6.

This howto is derived from an experience with SFR, in France (FTTH residential access). It might apply to other ISPs as well. In the case of SFR, steps 1 and 2 require an authentication. Fortunately, the L2TP password is hardcoded. The PPP password is not, but it's sent as cleartext, so a simple sniffing is enough to recover it.

# /etc/config/network
config interface 6pe
        option proto l2tpv2
        option server <LNS address>
        option username '<PPP username>'
        option password '<PPP password>'
        option keepalive '6'
        option ipv6 '1'
 
config interface 'wan6'
        option device '@6pe'
        option proto 'dhcpv6'

If you need authentication at the L2TP level (before PPP):

# /etc/xl2tpd/xl2tp-secrets
* * my_l2tp_password

At this point, running service network reload or simply running ifup wan6 should give you a fully working IPv6 setup. To debug, look at the logs (logread) and the interfaces status (ifstatus 6pe and ifstatus wan6).

Advanced options for this protocol are below.

Most options are similar to protocol “ppp”.

The name of the physical interface will be “l2tp-<logical interface name>”.

6to4 is the simplest IPv6 tunneling mechanism and relies on publicly available gateways.

The package 6to4 must be installed to use this protocol.

# /etc/config/network
config interface 'wan6'
        option proto '6to4'
 
# /etc/config/firewall
config rule
        option target 'ACCEPT' 
        option name '6to4' 
        option src 'wan' 
        option proto '41'

If you choose a name for your tunnel-interface different from wan6, be sure to add that network to the wan firewall-zone.

See below for advanced configuration options.

This protocol type does not need the device option set in the interface section. The interface name is derived from the section name, e.g. config interface wan6 would result in an interface named 6to4-wan6.

ds-lite is a transitioning-mechanism which is used by ISPs to support legacy IPv4-connectivity over a native IPv6 connection.

The package ds-lite must be installed to use this protocol.

The configuration is usually auto-detected and manual configuration is not needed, simply installing the ds-lite package (and restarting the network interfaces like when changing the configuration) is usually enough.

# /etc/config/network
config interface 'wan6'
        option device 'eth1'
        option proto 'dhcpv6'
 
config interface 'wan'
        option proto 'dslite'
        option peeraddr '2001:db80::1' # Your ISP's DS-Lite AFTR

If you choose a name for your tunnel-interface different from wan, be sure to add that network to the wan firewall-zone.

See below for advanced configuration options.

ds-lite operation requires that IPv4 NAT is disabled. You should adjust your settings in /etc/config/firewall accordingly.

This protocol type does not need the device option set in the interface section. The interface name is derived from the section name, e.g. config interface wan would result in an interface named dslite-wan.