Why aren't I getting full gigabit ethernet speeds from AC88U?

[mdee4]

Setup: I had AT&T Gigapower(Fiber 1gbps up/down) installed recently. I have the gateway/modem(Pace 5268AC) plugged into my AC88U router. I then have LAN port 1 of router connected to a TP-Link 8-Port Gigabit Ethernet Desktop Switch (TL-SG108). From there, I have ethernet cables plugged into the switch that go to all the ethernet ports around the house.

Problem: My problem is the router is only sending 100mbps speeds through LAN 1 port(see screenshot). The switch shows that the router is sending 100 and that my computer can receive 1000. Now all my Ethernet ports are getting 100mbps instead of around 600mbps if it was 1000 Full Duplex.

Anyone have any idea why the router is passing 100 Full Duplex through the LAN 1 port to the switch instead of 1000 Full Duplex?
Anything I can test, aside from replacing the cables, as brand new cables were used in this setup?
Is there a way I can force 1000 Full Duplex for LAN 1 port and see if that helps?

All ethernet cables used are Cat 5E. Also, if I plug my computer directly into AC88U, then I'm not limited to 100mbps. AC88U is using ASUSWRT-Merlin firmware 380.64_2.

Thanks for any advice/help!

 

[Zirescu]

Your TP-Link switch might be dropping down to a lower speed when it's idle. You validated that the AC88U port when connected directly to your computer is giving 1000 so the issue is likely with the TP-Link and not the AC88U.

 

[mdee4]

Your TP-Link switch might be dropping down to a lower speed when it's idle. You validated that the AC88U port when connected directly to your computer is giving 1000 so the issue is likely with the TP-Link and not the AC88U.

When I plug my computer into the switch(port 2), it shows 1000 for that port, but 100 for the port connected to router(port 1). If what you say is true, then shouldn't port 1 on the switch change to 1000 since it's no longer idle?

 

[sfx2000]

When I plug my computer into the switch(port 2), it shows 1000 for that port, but 100 for the port connected to router(port 1). If what you say is true, then shouldn't port 1 on the switch change to 1000 since it's no longer idle?

Suspect cable...

It happens - some network cards are overly sensitive to this - esp. RealTek cards...