You will first need the client program found in the Debian called ‘gogoc‘, if you want to use ‘router‘ mode you’ll also need to install ‘radvd‘ too which is also available in Debian.

Edit the ‘/etc/gogoc/gogoc.conf‘ file to suit:

userid=yourinternodeusername
passwd=yourinternodepassword
server=sixgw.internode.on.net
auth_method=any
host_type=router
prefixlen=64
if_prefix=yournormalinterface
dns_server=192.231.203.132
gw6_dir=/usr/local/gw6c
auto_retry_connect=yes
retry_delay=30
keepalive=yes
keepalive_interval=30
tunnel_mode=v6anyv4
if_tunnel_v6v4=gif0
if_tunnel_v6udpv4=tun0
if_tunnel_v4v6=
client_v4=auto
client_v6=auto
template=linux
proxy_client=no
broker_list=tsp-broker-list.txt
last_server=tsp-last-server.txt
always_use_same_server=no
log_filename=gw6c.log
log_rotation=yes
log_rotation_size=32
log_rotation_delete=no
syslog_facility=USER

When you first start gogoc it will try to make a secured connection to the Internode tunnel broker. The problem is that when you run gogoc for the first time it will fail with ‘Not starting gogoc - no server key ... (warning). failed!‘ cause it was unable to accept the server key from Internode. This means that we have to run gogoc from command line, like this:

# gogoc -n
sixgw.internode.on.net is an unknown host, do you want to add its key?? (Y/N) y
^C

Now you should be able to start ‘gogoc‘ as a deamon now with

# invoke-rc.d gogoc start

Testing it all works:
To see that you have an active tunnel working from command line, like this:

# ifconfig  | egrep '(Link|inet6)'

and you should get an output something like this:

...
tun       Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
          inet6 addr: 2001:44b8:61::239/128 Scope:Global

now you should be able point your web browser to see the swimming turtle at http://www.kame.net/, also you should be able to see your IPv6 address here at Internode’s IPv6

Reference:
Internode’s IPv6 tunnel broker for Fedora Linux
Gentoo IPv6 Router Guide