This are my personal notes took from the Linksys Community Forum for the EA6900 Router... just in case I forget about it in the future.
Community:The Linksys Community discuss things about this router at: http://community.linksys.com/t5/Wireless-Routers/bd-p/Wireless_Routers
More Information:This are some tips about the router:
Advanced Wireless Settings: /dynamic/advanced-wireless.html
Problem 1 - Internet Connection Drop:The router used to have a flaw that looked like the Internet Connection Drop, but if you have a wired PC connected to it with DHCP of fixed IP it will be working and you can access the router. If you switch off and then on the Wifi it will start woking again. So it was a problem of the Wifi dropping.
This was fixed with Firmware version: 18.104.22.168129 (2014/06/05)
Source: Linksys Forum Discussion.