For slow wired devices on an Archer, TP-Link's guidance is to test in layers. Connect a computer straight to the modem and run a speed test, then connect the same computer to the router by cable and compare. Swap the modem-to-router cable for Cat6 or better. Try a different LAN port and a second computer. Check the port and adapter speeds: a 100 Mbps adapter or cable caps you near 100 Mbps whatever the plan, and multi-gig ports like the 2.5G and 10G ports on the Archer BE900 need matching cables and devices.
The checks in more detail
On single-LED routers TP-Link describes a speed negotiation problem where forcing the internet port to 100 Mbps full duplex under Advanced, Internet, Internet Port Negotiation Speed Setting clears a WAN Port Unplugged message, which is a workaround, not a speed goal. Disable QoS and Parental Controls to test, and make sure the router is not overheating. If the modem-to-router link negotiates slowly, replace the cable first.
If a device on a switch is slow, connect it straight to the router to remove the switch. Reset only if the router's own behavior is odd. A link light that shows the wrong speed is the quickest clue you will get, so look at the port and the device's network status together before you replace anything, and test the same cable in another port. Run a long cable in a loose loop, not a tight bend, because a kinked cable is a common hidden cause of a link that will not reach gigabit.
If you have a cable tester or a second cable, swap them along the run one section at a time, since a bad wall plate or coupler is a common hidden cause of a link that negotiates at 100 Mbps. Use the router's own status page to see the negotiated speed of each port where it is shown, since it removes guesswork about whether the link is running at gigabit or 100 Mbps.
Differential
Likely causes of “TP-Link Archer routers Ethernet link is limited to 100 Mbps or disconnects”, and how to tell them apart
- 1
A 100 Mbps cable or adapter
What separates it The wired speed is capped because the cable or the adapter only runs at 100 Mbps
How to confirm Use a Cat6 cable, and check the adapter on the device, then test the speed again
- 2
A bad port
What separates it One port is slow because that port on the router has a fault
How to confirm Try another port on the router, and see whether the speed improves
- 3
Speed negotiation on the WAN
What separates it The web page says WAN Port Unplugged because of a speed negotiation problem
How to confirm Force the WAN port to 100 Mbps as a workaround, as TP-Link describes for this fault
- 4
QoS or Parental Controls
What separates it The speed is reduced because QoS or Parental Controls is switched on
How to confirm Disable them as a test, and see whether the speed improves
- 5
A switch in the path
What separates it The speed is limited because a switch sits in the path between the device and the router
How to confirm Test without the switch, by plugging the device straight into the router
Before you touch a setting
Record this first — changing settings destroys the evidence
- The type of cable that you are using
- The speed of the port and of the adapter on the device
- Speed at the modem and the router
- Whether a switch is in use
Try in this order
0 of 7 completedTest at the modem
ReversibleTest at the modem with a computer connected directly, to see the speed that you are getting.
Test at the router
ReversibleTest at the router with the same computer, and compare the result with the one at the modem.
Swap the cable
ReversibleSwap the cable for a Cat6 or better cable, and check the speed again, and then test again to see whether it helped.
Swap the port
ReversibleSwap the port by using another LAN port on the router, to see whether the first is at fault.
Check the adapter
ReversibleCheck the adapter on the device, since an adapter that runs at 100 Mbps caps the speed.
Disable QoS
ReversibleDisable QoS as a test, and see whether the wired speed improves after that, and then test again to see whether it helped.
Remove switches
ReversibleRemove any switches from the path for the test, so that only the router is in between.
Model-specific
What is true of this model and not of its siblings
- BE900
- The Archer BE900 has 10G and 2.5G ports.
- AX55
- The Archer AX55 has gigabit ports.
- Other models this page answers
- These steps also fit the Archer BE550 Wi-Fi 7 router, Archer AXE75 router, Archer AX73 router, Archer AX55 router.
Stop boundary
When this stops being a self-service repair
- !If a known-good cable and port stay slow, contact TP-Link support
- !If the modem is slow, call the provider
- !If one device is slow, check its adapter
Evidence ledger
Sources behind this answer
TP-Link's own product page for the Archer BE900 with its 10G and 2.5G ports.
Modem test, channel width, QoS and overheating.
RJ45 cable, modem test and WAN port test.
Internet IP, MAC clone and LAN IP.
Reset button and web reset.
The company and its products.
Exact questions
Common questions
Why is my wired speed 100 Mbps?+
The usual cause is a 100 Mbps cable, port or adapter, so check all three of them.
What does forcing 100 Mbps do?+
Forcing 100 Mbps is a workaround for a speed negotiation fault on the WAN port.
Do multi-gig ports need special gear?+
Multi gig ports need a matching cable and a device that can also run at that speed.
Can QoS slow wired speed?+
Yes, QoS can slow wired speed, so disable it as a test to find out.
Should I test at the modem?+
Yes, test at the modem first, to get a baseline speed to compare against.
Can heat matter?+
Yes, heat can matter, since an overheated router slows down and may drop connections.
Can a switch limit speed?+
Yes, a switch in the path can limit the speed, so test without it.
Do I need a reset?+
Only reset the router if it behaves oddly after all of the other steps.