Very strange problem, could it be a faulty Billion 7800N?
Router has been working satisfactorily since purchase. Zen FFTC with BT openreach modem. Connected via 8 port switch to desktop pc's, windows home server, printers and wirelessly to several laptops and ipads/iphones.
Recently suddenly all internet connectivity was lost on all devices, with messages about inability to resolve DNS. Router and modem showed internet connected, both externally and on setup pages. The DNS settings were altered in the router to both obtain automatically and set manually but still could not connect any devices. By changing the network property settings on each device to fixed DNS server addresses, all could again connect. Worked but not ideal. I rebooted all machines and router, checked ipconfig and set ipconfig /flushdns, but never worked until DNS servers manually entered into windows 7 network settings.
THat works, but would prefer it to work automatically for other and new devices. Now having problem with ipads. They cannot connect to the internet, and bizarrrely when I renew the network lease, they obtain a valid ip address, which then changes in front of my eyes to an ip address outside the DHCP range set in the router! THe router uses a mixture of fixed ip addresses for the server & printers, and DHCP for everything else. The ranges are completely separate. The ipad gives the correct wireless SSID, but repeatedly changes the ip address and incorrect DNS servers. Same with the iphones.
I have a separate wireless network (mainly for backup) with a separate ADSL connection to plusnet, and I can correctly connect the mobile devices to that router.
So in summary : everything has been working fine for some time since router was set up. Suddenly all devices are unable to obtain DNS settings unless they are fixed in network settings and mobile devices appear to be obtaining invalid ip addresses. All devices work fine with alternate network, and ipconfig shows all devices correctly have the router as DNS gateway.
Could this be a faulty Billion? I am intending to also post on the Billion forums, but am having trouble registering.