My provider don't provide ipv6, so I setup ipv6 with HE tunnel broker (I've used tutorial from troywitthoeft).
I've checked ipv6 status with test-ipv6.com and got 10/10, then I ping6ed ipv6 version of google, ipv6-test. It worked. I even opened ipv6 version of google with Firefox. But I couldn't open some sites, for example, subnetonline, ipv6-test (they worked fine without ipv6 tunnel).
I've remembered that sometimes changing MTU size fixes this. I've tried to change MTU simultaneously in Tomato USB ipv6 tunnel settings and in tunnel broker settings but it didn't help much. It seems to me that by reducing MTU down to 1472 I got subnetonline work sometimes, but other sites still not loading.
I've uploaded my configuration to imgur (I've deleted some digits to save privacy), but due low carma I cannot insert images and links. See H00IQZB.png on imgur.
I have Tomato Firmware 1.28.0000 MIPSR2-117 K26 USB VPN by Shibby installed on my Netgear WNR3500L. PC: Lenovo x230, openSUSE 13.1, Network Manager.