From the dualstack-is-fun department...

Daniel Roesen dr at
Mon Feb 28 23:33:33 CET 2011

Windows 7 laptop, Virtualbox 4.0.4, Fedora 14 guest VM, bridged
networking to host WiFi connection.

IPv6 half-broken (
RAs do get through to the guest VM, Linux SLAACs and sets default route
to the advertising router. ND to default router fails though, as
neighbor advertisements do get eaten between host and guest VM.

Firing up Firefox (3.6.13), trying to surf to dualstacked websites.

DS-Website having one AAAA RR:  ~3 minutes time to IPv4 fallback(!)
DS-Website having two AAAA RR: ~13 minutes time to IPv4 fallback(!!!)

Yes, minutes, not seconds. Every non-technical user will certainly give
up before fallback happens.

Seriously, I think we operators would be well advised to help reviewing
and polish up the Happy Eyeballs spec and - if deemed feasible - promote
implementation to OS/Distro/App vendors ASAP.

Happy Eyeballs ain't unproblematic. Opportunistic session setup will
have impact on - if the IPv6 transport of a dual-stacked target host
works fine, the opportunistic IPv4 session setups will "unnecessarily"
(as no data traffic transfer follows) clog up resources on LSNAT44
and the target firewalls, loadbalancers and host (phantom sessions).
See section 4.2.1

So I'll encourage everybody to join the IETF v6ops mailing list and
provide input. I think it's really important and we're running out of

Best regards,

CLUE-RIPE -- Jabber: dr at -- dr at IRCnet -- PGP: 0xA85C8AA0

More information about the ipv6-ops mailing list