@mogsiewp I have been following this thread and cannot believe the stupidity and total lack of understanding of Google support. There is no VLAN tag on the LAN connection from the modem, so their obsession with VLAN tagging is just not a valid excuse for the problem. Also the nonsense about Gateway IP addresses is just beyond belief, a Private Gateway address is perfectly valid. As for adding a switch or router between the modem and Nest how can that achieve anything if there is no VLAN tag there, you can't remove something that isn't there!
The
"Google Help Page" about VLAN tagging confirms that it is not the problem.
Set up a network that uses VLAN tagging
**Some Internet Service Providers (ISP) require VLAN tagging in order for their modems to communicate with wireless routers.
Note: VLAN tagging is not supported by Google Nest Wifi or Google Wifi and can cause your setup to fail.
To confirm if your ISP uses VLAN tagging, or if you have IPTV or VoIP service through your ISP, check with your ISP.
There is no VLAN Tag going to the router so the sentence marked ** does not apply. The onhub file confirms you have a valid PPPoE connection and you are online. The vlanScan lines are somewhat ambiguous, it hasn't attempted to scan but the scan is complete. I don't see how that would confirm there is a VLAN tag. If there was a VLAN problem you would not get any connection.
VLAN tagging can be a problem if the ISP does uses it so the router can identify different services such as VOIP or IPTV but this does not apply to Openreach FTTC connections. (Seems to be on US and some Continental ISPs)
What I would like to clarify is when you see the WI-FI drops is the Internet still connected, is the PPPoE connection still up? Your earlier post suggested it was just the wi-fi dropping but could you confirm this?
There is nothing to be gained by trying to run the HG612 in Router mode, as @Alex_Atkin states it probably doesn't have the processor power to run PPPoE which is quite demanding on high speed connections. I wouldn't even bother to try it and you will probably end up with a Double NAT situation.
My conclusion is that this is a Wi-Fi problem with the Google Nest but you are going to struggle to get them to accept this.
I don't think you will get a satisfactory result.