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Comment by amyjess | Hacker News Reader

I don't use IPv6 even though my ISP supports it, because every time I try to enable it, it causes all my network connections to randomly choke.

This has happened with every Linux desktop I've ever used. If IPv6 is enabled, then half the time I try to visit a website, the connection doesn't go through. No error either; it just sits there forever and ever. It's particularly aggravating when AJAX is involved--you get to experience Google Maps stop working for about five minutes while you're using it.

I've observed it across multiple Linux distributions for several years now. I've learned to always add "ipv6.disable=1" to my sysctl.conf if I want a working network.

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That's very, very, very strange. I've been running IPv6 (first through a tunnelbroker.net tunnel, and -much- later using native IPv6 through Comcast) for roughly eight years now. Haven't had any issue with Linux, Mac, or Windows systems.

To diagnose a thing, what happens when you disable Router Advertisements on your router, then enable IPv6 on a machine, and run Teredo [0] on that machine? (After Teredo assigns an IPv6 address to the teredo virtual interface, start a 'ping6 google.com'. It will take a few minutes for the Teredo machinery to figure out how to make a connection, but it should eventually do so.)

Are you -perhaps- rejecting or dropping ICMP on your router? If you are, don't. ICMP is required to make IPv6 work.

[0] This is the Teredo implementation that people use on Linux systems http://www.remlab.net/miredo/

I'll have to look into this sometime.

Thanks for the advice!

Maybe an mtu issue. Path mtu usually makes things work, but the isp end of the connection may be rate limiting sends; if everyone else is getting bad settings too, it's not pretty.

Just a thought, but try this; re-enable ipv6 and then add:

'options single-request' to the end of /etc/resolv.conf

Let me know if you try it and it works.

That is very odd and must have something to do with your setup or ISP. I worked at a company where all of us had Linux desktops and we all used IPv6. I never had any issues.

Also, remember with IPv6 has entirely different firewall rules. Remember to setup ip6tables. You might be totally protected on ipv4 and totally exposed on ipv6.

Do you have a firewall that drops ICMP packets? Some firewall admins do this believing it improves security, but it can cause exactly this to happen.

You can usually get away with it in IPv4, but with IPv6 it causes connections to stall as soon as you try to push any significant amount of data through a TCP connection.

Looks like either your ISP or your router is at fault.

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