I have this problem at 3 of my sites using a TOT Fiber Modem in the basic router mode.

If I change the local DNS on my machine to 8.8.8.8 or 208.67.222.222 then DNS requests time out. I can ping both these IP's with no issue. It looks like the modem is blocking outward DNS requests to anything but TOT's own DNS servers.

However, if I change the TOT Fiber Modem in to bridge mode and use my own equipment to make the PPPoE connection, then I can use Google / Open DNS just fine.

Does anyone else have this issue?

Okay I have TOT fiber at two locations and I have fiber transceivers not modems which go directly into my routers. I use GOOGLE DNS and OPENDNS and TOT DNS over many virtual nets. No problems. If you have a modem(or router) from TOT and it's routers/dhcp DNS settings are set to authoritive then this might explain your troubles and yes switching to bridge mode would fix it. No matter I would always run any tot equipment in bridge mode to give me the control.

gosompoi - can you recommend a make and model of fiber transceiver to connect to the TOT fiber? I'd much prefer to work this way as it takes TOT about a week to move the modem over to bridge mode.

gosompoi - can you recommend a make and model of fiber transceiver to connect to the TOT fiber? I'd much prefer to work this way as it takes TOT about a week to move the modem over to bridge mode.

Both Locations TOT provided a FREE transceiver which the incoming fiber lines terminated in and an ethernet out that connected to wan port of my router. The brand is a generic no-name, which I have also purchased 10 of the same kind from Advice.co.th (even swaped out when TOT failed.).

Which type of fiber do they use? Is it single or multi-mode?

Which type of fiber do they use? Is it single or multi-mode?

single

Update, TOT Just updated the routers for my area two days ago to support IPv6 and now the DHCP is supplying authoritative DNS with DNS masking. But I was still able to ignore their authoritative by using static/manual static IP settings on our main incoming routers wan settings. I would not have noticed their equipment swap except they made a gateway setting error which took one of our networks down temporarily. In diagnosing the error and correcting wan IP settings manually I noticed all my routers and computers were getting IPv6 information populated from the new upstream TOT equipment.