I'm trying to setup my linode with IPv6 using a HE Tunnel. I'm using an Ubuntu Linode and I've followed the instructions here using both the Debian and Ubuntu sections.

For whatever reason, this interface doesn't work. All packets sent from it seem to go into the bit bucket. For example:

server:~> ping6 ipv6.google.com
PING ipv6.google.com(pv-in-x68.google.com) 56 data bytes

--- ipv6.google.com ping statistics ---
5 packets transmitted, 0 received, 100% packet loss, time 3998ms

The output of the ifconfig command is below, and I'm interested in knowing what is wrong, but I'm also interested in learning what tools would be available for me to debug this type of issue in the future, too!

server:~>ifconfig
eth0      Link encap:Ethernet  HWaddr fe:fd:40:3e:be:7d  
          inet addr:64.62.190.74  Bcast:64.62.190.255  Mask:255.255.255.0
          inet6 addr: fe80::fcfd:40ff:fe3e:be7d/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2434892 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1855876 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:514489967 (514.4 MB)  TX bytes:950154288 (950.1 MB)
          Interrupt:28 

eth0:0    Link encap:Ethernet  HWaddr fe:fd:40:3e:be:7d  
          inet addr:64.62.190.125  Bcast:64.62.190.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:28 

hetunnel  Link encap:IPv6-in-IPv4  
          inet6 addr: 2001:470:1f04:66::2/64 Scope:Global
          inet6 addr: fe80::403e:be4a/128 Scope:Link
          UP POINTOPOINT RUNNING NOARP  MTU:1480  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:1366271 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1366271 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:147905132 (147.9 MB)  TX bytes:147905132 (147.9 MB)

Firewall? ip6tables?

ip6tables -nvL
route -6

Por favor. :-)

_________________
Disclaimer: I am no longer employed by Linode; opinions are my own alone.

I don't have a firewall installed, but here are the items you requested

server:~> sudo ip6tables -nvL
Chain INPUT (policy ACCEPT 104 packets, 8376 bytes)
 pkts bytes target     prot opt in     out     source               destination 

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination 

Chain OUTPUT (policy ACCEPT 126 packets, 10424 bytes)
 pkts bytes target     prot opt in     out     source               destination 

server:~> sudo route -6
Kernel IPv6 routing table
Destination                    Next Hop                   Flag Met Ref Use If
::1/128                        ::                         Un   0   1     5 lo
fe80::fcfd:40ff:fe3e:be7d/128  ::                         Un   0   1     0 lo
fe80::/64                      ::                         U    256 0     0 eth0
ff00::/8                       ::                         U    256 0     0 eth0
::/0                           ::                         !n   -1  1     2 lo

It seems that there is no default route for IPv6, however, I'd guess that is correct, because the IPv6 traffic should be tunneling through IPv4. Am I right?

Thanks again for the help!

I've tried a billion ways to get it to work in /etc/network/interfaces but none of them worked until this, ymmv

auto 6in4
iface 6in4 inet6 v4tunnel
    endpoint <Remote IPv4>
    local <Local IPv4>
    ttl 255
    address <Local IPv6>
    netmask 64
    mtu 1480
    up ip -6 route add ::/0 dev 6in4 metric 1
    post-up sysctl -w net.ipv6.conf.all.forwarding=1

Dont know if last line is required or not

and here is my routing table for comparison:

Kernel IPv6 routing table
Destination                    Next Hop                   Flag Met Ref Use If
::1/128                        ::                         Un   0   1  1171 lo
2001:470:1f04:54d::/128        ::                         Un   0   1     0 lo
2001:470:1f04:54d::2/128       ::                         Un   0   1 94079 lo
2001:470:1f04:54d::/64         ::                         Un   256 0     9 6in4
fe80::/128                     ::                         Un   0   1     0 lo
fe80::42a0:8d94/128            ::                         Un   0   1     0 lo
fe80::fcfd:40ff:fe3e:e756/128  ::                         Un   0   1     0 lo
fe80::/64                      ::                         U    256 0     0 eth0
fe80::/64                      ::                         Un   256 0     0 6in4
ff00::/8                       ::                         U    256 0     0 eth0
ff00::/8                       ::                         U    256 0     0 6in4
::/0                           ::                         U    1   0     0 6in4
::/0                           ::                         !n   -1  1     1 lo

It's not.