Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

On my VDS, both 6to4 and Teredo seem to work poorly (packet loss is about 40%). shows packet loss 10%-80% both for 6to4 and for Teredo address, but 0% for IPv4 address.

When running ping6 -n and tcpdump -n 'host' I see more ICMP6, echo request packets going to than ICMP6, echo reply coming back from

How to debug it? Is 6to4 unreliability probably caused by misconfiguration on my side or problems on some remote side?

share|improve this question
Meanwhile have just configured the HE tunnel and see no lost packets there. – Vi. Mar 28 '13 at 0:18
6to4 is just naturally unreliable. Get a tunnel, or better yet a VPS provider with native IPv6. They are starting to show up in greater quantities now. – Michael Hampton Mar 30 '13 at 2:22
I have never yet seen any native IPv6 on any hosts I've logged into. (actually I rarely see non-NAT-ted IPv4 as well). – Vi. Apr 1 '13 at 13:22 – Michael Hampton Apr 1 '13 at 15:27
up vote 0 down vote accepted

Debugging 6to4 problems is almost impossible. Your outgoing 6to4 traffic (to non-6to4 destinations) will go to the IPv4 address There are multiple public 6to4 relays on the internet for that address. You would need to do a traceroute to to find out which one you are currently (it changes over time) using. That is one bit of information. Then it depends which IPv6 destination you are connecting to. They will use the closest 6to4 relay for them. It is almost impossible to find out which relay they are using.

Either of those relays might be causing packet loss.

share|improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .