OK I have a Linksys WRT160N V3 and an Asus RT-N12 B1 both running your MOD (K26 MIPSR2 and K26 RT-N), newest version, with he.net's IPV6 tunnel. I have a Nexus 4 running Android 4.4.2, when connected to WiFi, stay for a while (a few hours) and IPV6 gateway disappear. Both router I mention above cause this problem. Using other routers as AP causes same problem. I turn off WiFi optimization in the phone's setting (this should reduce power usage when connected to WiFi) and IPV6 always works (with any AP). Meanwhile IPV4 always works no matter which AP I am using and no matter WiFi optimization is on or not. All wired devices work fine. All notebook PCs connected with WiFi work fine. I have asked Google and they said that this is not their fault. Can you spare some time to find out what's going wrong? Thanks.