I am a software engineer and have some training and experience with TCP/IP networks, but not enough to figure out this intractable issue that appears to be caused by my choice of router colliding with my choice of broadband provider.
My home network has a Hyperoptic (UK) 1Gbps broadband connection delivered directly as Ethernet. The apartment has an incoming Hyperoptic Ethernet port on the wall. There is no modem or cable service, only pure Ethernet TCP/IP. A Google Nest WiFi router is plugged into the incoming Ethernet socket using CAT6e cabling, the router is configured in NAT (not bridge) mode and all in-home devices then connect to the router over WiFi (with a handful connected via an unmanaged switch connected to the router. The router has a public, static IPv4 address assigned by the ISP's DHCP server (to bypass their CGNAT).
The configuration generally works well and Ethernet devices achieve 600Mbps+, whilst WiFi devices achieve 300Mbps+. However, every few weeks the two smartphone apps (on both iOS and Android) used to control the router (Google WiFi and Google Home) lose all contact with the router, which I expect is implemented by Google's cloud services. The apps show the router as "Offline" when it definitely is not and the router then cannot be configured, and the 48-hourly automated speed tests do not happen (I expect the trigger is from Google's cloud services supporting the routers). Rebooting the router fixes the issue but it then recurrs a few days later.
The question I ask myself is if the router can deliver 600Mbps, why has the router lost its connection to the Google cloud services that support app router control?
I also use the Todoist web app in Chrome on a MacBook and I notice that also fails to regularly sync, manual syncs are needed as it loses its connection. Todoist says there are no known issues that could cause it, and so it's possible this is another symptom of the same network issue (it may just be a Todoist issue though). No other network devices or applications show any issues.
I've traded 70+ emails with Google support about the router. They say that my ISP is using VLAN tagging and the router does not support VLAN tagging. The ISP offers broadband and VoIP service, I suspect perhaps VLANs are used to segment, though I do not use the VoIP service.
Google also says that as my router's gateway IP address "ends in 223 not 1 or 254 that means your ISP is using VLAN tagging". Is this true? I'm at the limit of my knowledge here. I thought the gateway IP ending in 1 was more by convention than a requirement?
Even when using a router that doesn't support VLAN tagging, if in practice there's no segmentation occurring (only broadband data, no VoIP) is it reasonable to think the router should just ignore tags, and should work OK? If my network was actually segmented into VLANs I'd obviously expect a router that doesn't support VLANs to not work, but the VLAN tagging serves no purpose as there's no segmentation.
If I were to keep the Google router, is there an easy way to strip the VLAN tags? e.g. if I get an ISP router and insert it between the incoming Ethernet and the Google router, might that be likely to strip them? The ISP suggests no, but I'm not sure they understand the question. It would mean another NAT network and might affect performance.
I appreciate many people prefer a local-only router and you might suggest I use another brand, but when it works I appreciate the speed and ease of configuration the Google router provides but replacing it is an option if necessary.
I would greatly appreciate any help with answers to my questions to better understand how VLAN tagging works in a scenario such as this.
