IPv6 tunnel broker setup

This article introduces a method for obtaining an IPv6 address using 6in4, also known as SIT.

The following sections will use the tunnel service provided by Hurricane Electric as a setup example. Hurricane Electric offers a free tunnel broker service to add IPv6 connectivity to an IPv4-only host. Read the "Tunnel Broker" section of their FAQ for a list of prerequisites.

Registering for a tunnel

Registering for a tunnel on its website.

Setting up Hurricane Electric tunnel

There is some ways you can achieve this, such as using the ip command to test the tunnel manually, a custom systemd unit, or using a Network Manager like #systemd-networkd.

Custom systemd unit

Create the following systemd unit, replacing bold text with the IP addresses you got from Hurricane Electric:

Note: If you are behind a NAT (typical home router setup), use your local IPv4 address for client_IPv4_address, e.g. 192.168.0.2.

/etc/systemd/system/he-ipv6.service

[Unit]
Description=he.net IPv6 tunnel
After=network.target

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/usr/bin/ip tunnel add he-ipv6 mode sit remote server_IPv4_address local client_IPv4_address ttl 255
ExecStart=/usr/bin/ip link set he-ipv6 up mtu 1480
ExecStart=/usr/bin/ip addr add client_IPv6_address dev he-ipv6
ExecStart=/usr/bin/ip -6 route add ::/0 dev he-ipv6
ExecStop=/usr/bin/ip -6 route del ::/0 dev he-ipv6
ExecStop=/usr/bin/ip link set he-ipv6 down
ExecStop=/usr/bin/ip tunnel del he-ipv6

[Install]
WantedBy=multi-user.target

Then start/enable he-ipv6.service.

Tip: To test you can run the above commands following ExecStart manually to setup a temporary tunnel. It will not persist after reboot.

systemd-networkd

If systemd-networkd handles your network connections, it is probably a better idea to let it handle tunnel broker too (instead of using a .service file).

/etc/systemd/network/he-tunnel.netdev

[Match]
 
[NetDev]
Name=he-ipv6
Kind=sit
MTUBytes=1480
 
[Tunnel]
# IPv6 Tunnel Endpoints|Server IPv4 Address
Remote=216.66.80.30
# Local IPv4 | NAT-Address
Local=192.168.0.2
TTL=255

/etc/systemd/network/he-tunnel.network

[Match]
Name=he-ipv6
 
[Network]
# IPv6 Tunnel Endpoints|Client IPv6 Address>/64
Address=2001:470:NNNN:NNNN::2/64
# IPv6 Tunnel Endpoints|Server IPv6 Address
Gateway=2001:470:NNNN:NNNN::1
DNS=2001:4860:4860::8888
DNS=2001:4860:4860::8844

[Route]
# IPv6 Tunnel Endpoints|Server IPv6 Address
Gateway=2001:470:NNNN:NNNN::1
Destination=::/0

[RoutingPolicyRule]
# IPv6 Tunnel Endpoints|Client IPv6 Address>/64
From=2001:470:NNNN:NNNN::2/64

[RoutingPolicyRule]
# Routed IPv6 Prefixes|Routed 64>/64 - OR - Routed IPv6 Prefixes|Routed 48>/48
From=2001:470:NNNN::/48

Replace all NNNN to your own address.

And, add this line to [Network] section of your default Internet connection .network file:

/etc/systemd/network/DEVICE.network

Tunnel=he-ipv6

Using the tunneling with dynamic IPv4 IP

Updating via cron job

The simplest way of using tunnelling with a dynamic IPv4 IP is to set up a cron job that is going to periodically update your current address. The example URL and an Update Key can be found in the Advanced tab of the Tunnel Details page.

To check if the update works, run the following command (replace USERNAME, UPDATEKEY and TUNNELID by the details of your account and tunnel):

$ wget -O - https://USERNAME:UPDATEKEY@ipv4.tunnelbroker.net/nic/update?hostname=TUNNELID

If it works, create a cron job by opening crontab -e and adding a new line:

*/10 * * * * wget -q -O /dev/null https://USERNAME:UPDATEKEY@ipv4.tunnelbroker.net/nic/update?hostname=TUNNELID

Updating via ddclient

Alternatively this can be configured by installing ddclient and configuring /etc/ddclient.conf:

protocol=dyndns2
use=web
web=checkip.dns.he.net
server=ipv4.tunnelbroker.net
ssl=yes
login=USERNAME
password=UPDATEKEY
TUNNELID

And finally start/enable ddclient.service.