@BritG1 There is a (typical) maximum length of a single Ethernet connection of 100 m or 328 ft.  Since you simply swapped the connection and it worked I suspect I can rule that out.  Cat 8 at 2.5 GbE is overkill unless the cables are defective.  (I bought one type from Amazon recently that failed to negotiate 10 GbE).

It's a shot in the dark:  But you can try cloning the MAC of the GigaSpire onto the primary Deco (connected to the ONT), or your PC MAC.  Also may try disabling Ignore Ping from WAN...

I looked up the specs and that gateway/modem they provide has dual 10 Gb Ethernet ports?  But at 2 Gbps service 2.5 Gb Ethernet should handle it nicely....

Thanks for the response.

The maximum cable length from the ONT is 50ft for 2 PCs and 100ft for one.

Yes, Cat 8 is overkill, but today the cost difference (today) is minimal and hopefully future proof. The 6 year old cables were not as neat as the new layout and I now have have a couple of spare runs.

- Ping from WAN is already disabled.

- I'll try the cloning you suggest, assuming I figure out how to do that. - I wondered if my provider was expecting a specific IP/MAC (BE 63 has no specifc WAN port) but since the MAIN unit is reporting 2GB+ it seems it cant be that.

- I wonder when the update to specify WAN port will reach the BE63?

  @BritG1 I am sometimes (from long ago past experience) paranoid that the ISP is trying to force you to use their equipment.  (Yes I am in partial acceptance that this practice may now be ancient).  My suggestion is to enable Ping from WAN, as their GigaSpire may accept it and they can catch you are using a 3rd party router.  (I know by default Decos disable Pinging from WAN from my own)...

EDIT-  From what I read of the GigaSpire your ONT may have 10 GbE WAN output....

I had a very knowledgable tech do the installation - he set up the ONT to my existing wiring and we checked out speed with and without their Router. It was 2GB on one PC and not the other so we concluded it may be my old cables, hence my replacing them.

 - 2 days later I noticed the speed dropped on the one that was 2GB.

- Eventually, .... I got the same tech back and we proved that 2GB was reaching the BE63.

- As such I don't think my ISP is throttling anything, as I mention above, my designated Main BE63 reports 2GB + but any PC HW connected to them speed tests at 1GB.

- Yes, the GigaSpire has 2 10GB ports, one is used for WAN.

- ONT direct wired to BE63 or via the GigaSpire makes no difference.

-  I also changed the BE63 designated as main, so I don't think its a single unit failure.

The only thing I havn't tried is using the GS router and trying to set all BE63's as AP's. Not sure how thats done or if it would work.

  @BritG1 You can set the BE63s as AP with Deco Mesh, by switching the mode in the primary Deco router.  As APs they can all connect directly to the main switch or in your case the GigaSpire, (and continue to Mesh per my understanding).  There is some loss of function such as HomeShield is sacrificed:

https://www.tp-link.com/us/support/faq/2399/

Thanks, yes. LV4 sent me details on that in another thread, unfortunately, its a fairly large list of features that are lost.

• I plan to save the current config and then try AP so if it doesn't work I can easily revert. I actually hope that doesn't fix the issue......
• I have a lot on at the moment so it will not be today.
• I still don't undertand why the ONT (modem) output once received in the BE63 at 2GB is not shared at that speed. What causes the speed to drop?
• The Specs of the product show it should pass at up to 3.5GB, so perhaps its a Firmware/SW issue.
• Its perhaps no coincidence that other SW updates now allow 1 of the ports to be congifured as WAN on some other devices.

  @BritG1 Actually QoS does hold back bandwidth to the first device, for 2nd device, etc to have immediate availability.  Sorry I forgot to ask about this.  (It is common issue on ASUS routers but I did not know TP-Link suffers the same)...