Hi there, I know it may seem a common problem but after so many years and many routers I never had such an annoing problem.
Im in canada with telus, my 6900 freezes at least once a day with no access to LAN or WAN, I have to unplug the power and then works again for a few hours (sometimes a day).
I tried to revert back to the original firmware with the same result.
It seems that when the IP changes the router freezes (but again It may be just a coincidence since after a forced rebood the IP on telus changes).
I use custom (Unotelly DNS)
My previous E3000 was very stable, so was my WRT54G (all with DD-WRT).
I only have IP4 active (IP6 disabled), UPNP disabled, Media priorization disable and so many other but problem is still there.
Im in canada with telus 50 with an ALU modem.
This seems a software bug to me.
Any help is really appreciated.
Ps I bought the router from linksys USA and then moved to canada