1000Mbps Full Duplex Devices keep getting reduced to 100Mbps full duplex speeds on wired Ethernet.
I have bent over backwards trying to diagnose this issue, my BGW320-500 nearly every day now despite removing, replacing, isolating and diagnosing every device on the wired portion of the Router continuously reduces my network from Gigabit to 100Megabit speeds. The result of this is, my NVR stops working in HD, my 2 PC's cannot use Gigabit speeds they are restricted to 100MBit.
If i restart the BGW320 everything goes back to normal for about 24 hours, then the next day......... back to 100MBit.
I have 1 switch that breaks down LAN Port 1 to a TPLink 8 port gigabit switch, i have replaced that with a Linksys Gigabit 8 port switch but the same thing continues to occur. Something at the router continuously reduces my LAN Speeds to 1/10th of what I am paying for.
I have isolated multiple wired devices, 2 printers ( both run in Gigabit Ethernet ), my NVR which then cuts off my remote access to the NVR Feeds, i have removed each PC and over the last 7-10 days every day now, i find my LAN Speeds are STILL being cut back to 100MBit.
Do I need to have my BGW-320 replaced?
Additional info, i do have a Roku on Port 4 which is 100Mbit itself, but this should not be affecting Port 1, as Port 1 has its own settings. Port 3 is a XBox Series S, which is gigabit, and has never had a problem with reducing to 100MBit. Port 2 runs to a Samsung Smart TV and has no issues.
Additional things done - IPv6 LAN - disabled
Port 1 is forced to 1G Full Duplex mode - Router seems to ignore this and still cuts back Port 1 to 100MBit.
Ethernet Cables - Checked for sharp bends, nicks and/or cuts in insulation - none. No extreme RFI/EMI running near Ethernet or Hi-Volt sources running parallel to them.
PC/Printer/NVR Settings - all show 1000 Full Duplex as selected mode.
Restarted Modem using power down for 60 seconds by power plug - temporary fix
Any additional info or help would be appreciated.