I've got four tunnels, which generally work great. Two are to home routers, which dole out addresses from the /64, and two are to servers.
They all can get to various IPv6 hosts (ipv6.google.com, www.kame.net) with no problem. There are six possible connections between the four networks, and five of those connections work great. But there's one pair of tunnels that can't talk with each other.
Ping fails. TCP connections actually succeed, but only after waiting a loooong time.
Here's a trace from an autoconfigured machine on the 2001:470:1f0f:41e::/64 network to 2001:470:1f04:9dc::2:
traceroute to 2001:470:1f04:9dc::2 (2001:470:1f04:9dc::2), 30 hops max, 40 byte packets
1 2001:470:1f0f:41e::1 (2001:470:1f0f:41e::1) 0.823 ms 1.952 ms 2.453 ms
2 2001:470:1f0e:41e::1 (2001:470:1f0e:41e::1) 66.509 ms 70.611 ms 75.823 ms
3 gige-g2-14.core1.dal1.he.net (2001:470:0:78::1) 76.376 ms 76.520 ms 77.360 ms
4 10gigabitethernet1-2.core1.lax1.he.net (2001:470:0:3a::1) 109.156 ms 109.640 ms 110.471 ms
5 10gigabitethernet1-3.core1.pao1.he.net (2001:470:0:34::1) 117.231 ms 117.637 ms 128.805 ms
6 gige-g1-4.core1.fmt2.he.net (2001:470:0:30::1) 120.205 ms 119.935 ms 119.250 ms
7 1g-bge0.tserv3.fmt2.ipv6.he.net (2001:470:0:45::2) 119.886 ms 108.530 ms 113.776 ms
8 * * *
9 * * *
10 * * *
11 * * *
etc etc.
It fails on multiple machines on the 2001:470:1f0f:41e::/64 network, including a laptop that works on the other network. Is there something I'm doing wrong on the router? Thanks.
EDIT - Correction: I believe the TCP connection eventually works because it's giving up on IPv6 and uses IPv4.
Mayby routing is set unusualy on one of the machines.
On linux you could also use tcpdump to see the packets (icmp/pings).
traceroute to 2001:470:1f04:9dc::2 (2001:470:1f04:9dc::2) from 2001:470:1f0a:555::2, 30 hops max, 16 byte packets
1 piojan.tunnel.tserv6.fra1.ipv6.he.net (2001:470:1f0a:555::1) 40.616 ms 62.044 ms 42.475 ms
2 gige-g2-4.core1.fra1.he.net (2001:470:0:69::1) 40.076 ms 38.641 ms 38.211 ms
3 10gigabitethernet1-4.core1.ams1.he.net (2001:470:0:47::1) 45.991 ms 45.146 ms 48.077 ms
4 10gigabitethernet1-4.core1.lon1.he.net (2001:470:0:3f::1) 56.606 ms 69.582 ms 53.465 ms
5 10gigabitethernet2-3.core1.nyc4.he.net (2001:470:0:3e::1) 132.348 ms 122.665 ms 147.345 ms
6 10gigabitethernet3-1.core1.sjc2.he.net (2001:470:0:33::1) 202.463 ms 201.972 ms 201.818 ms
7 gige-g1-2.core1.fmt2.he.net (2001:470:0:31::1) 218.203 ms 217.286 ms 203.21 ms
8 1g-bge0.tserv3.fmt2.ipv6.he.net (2001:470:0:45::2) 206.112 ms 205.73 ms 204.395 ms
9 xan-2-pt.tunnel.tserv3.fmt2.ipv6.he.net (2001:470:1f04:9dc::2) 203.199 ms 204.047 ms 204.066 ms
$ traceroute6 2001:470:1f0f:41e::1
traceroute to 2001:470:1f0f:41e::1 (2001:470:1f0f:41e::1) from 2001:470:1f0a:555::2, 30 hops max, 16 byte packets
1 piojan.tunnel.tserv6.fra1.ipv6.he.net (2001:470:1f0a:555::1) 59.547 ms 42.831 ms 45.995 ms
2 gige-g2-4.core1.fra1.he.net (2001:470:0:69::1) 47.696 ms 47.525 ms 38.488 ms
3 10gigabitethernet1-4.core1.ams1.he.net (2001:470:0:47::1) 46.449 ms 50.519 ms 45.914 ms
4 10gigabitethernet1-4.core1.lon1.he.net (2001:470:0:3f::1) 72.409 ms 80.611 ms 54.833 ms
5 10gigabitethernet2-3.core1.nyc4.he.net (2001:470:0:3e::1) 122.449 ms 123.404 ms 123.934 ms
6 10gigabitethernet2-3.core1.ash1.he.net (2001:470:0:36::1) 129.149 ms 128.759 ms 128.877 ms
7 10gigabitethernet1-1.core1.dal1.he.net (2001:470:0:3b::1) 164.752 ms 163.938 ms 163.506 ms
8 1g-bge0.tserv8.dal1.ipv6.he.net (2001:470:0:78::2) 164.493 ms 171.376 ms 183.524 ms
9 2001:470:1f0f:41e::1 (2001:470:1f0f:41e::1) 229.076 ms 237.332 ms 232.594 ms
I had this problem as well and it turned out that routes were broken. I filed a support ticket and it was fixed a few minutes later. I was also told that one of my tunnels was on a really old tunnel server that dropping off causing this problem (it was the third time I had filed the ticket). I ended up moving to another tunnel server (delete tunnel, add new tunnel) and that is working.