Direct answer
For the NETGEAR Nighthawk RAX120 router, every cable pair, wall jack, switch and port must negotiate the intended speed. First, inspect negotiated speed and connect a known Cat5e+ cable directly.
What this covers
- NETGEAR Nighthawk RAX120 router (RAX120)
- NETGEAR router/mesh; modem integration, Wi-Fi generation, Armor, guest and Ethernet ports vary.
- The specific fault this record addresses: Ethernet link is limited to 100 Mbps or disconnects
What it does not cover
- ×The same symptom on a different NETGEAR product line, which has its own record and its own cited source
- ×An on-screen error code whose meaning has not been checked against this exact model's manual
- ×Live electrical, gas, sealed-system, internal battery-cell or structural repair — a technician boundary, not a self-service step
Differential
What actually causes this, and how to tell them apart
These are ordered by how often each one is the answer, not by how easy it is to try. The point of the middle column is that two causes producing the same headline symptom rarely produce the same detail — that detail is what tells you which one you have before you change anything.
- 1
The cable is a low category or is damaged
What separates it One run is slow or drops while others are fine, or the cable is old, kinked or thin.
How to confirm Swap in a known-good Cat5e or better cable of adequate rating for the speed you expect; a marginal or damaged cable caps or destabilises a wired link.
- 2
The port negotiated a lower speed than expected
What separates it The link works but at a fraction of the expected rate, and the port/link light or status shows a lower speed.
How to confirm Check the negotiated link speed on both ends; a gigabit device that comes up at 100 Mbps usually has a cable, port or auto-negotiation fault on that run.
- 3
A specific port is failing
What separates it Moving the same cable and device to another port restores full speed.
How to confirm Test the run on a different port; a fault that stays with one port and not the cable or device is the port.
- 4
The other device or its adapter is the limit
What separates it One computer or device is slow on a wire while another reaches full speed on the same port and cable.
How to confirm Compare a second device on the identical port and cable to separate the port from the client's own adapter or configuration.
Before you touch a setting
Record this first — changing settings destroys the evidence
Every item below stops existing the moment a reset, re-pair or settings change is made. Written down first, they are what separates the causes above; recovered afterwards, they are guesswork.
- The negotiated link speed shown on both ends of the slow run.
- Whether the problem follows the cable, the port, or the device when each is swapped.
- The cable's category rating and its physical condition.
Swap in a known-good adequately-rated cable
ReversibleA bad or low-category cable is the most common wired bottleneck.
Read the negotiated link speed on both ends
ReversibleA gigabit link coming up at 100 Mbps points at the cable, port or negotiation.
Move the run to another port to isolate a failing port
ReversibleIf the problem stays with the port, the port is the fault.
Test a second device on the same port and cable
ReversibleSeparates the network hardware from the client's own adapter.
Model-specific
What is true of this model and not of its siblings
Generic advice for the product line fails here. Each item below is a property of this specific model family that changes which of the steps above apply to you.
- Model scope
- RAX120. NETGEAR router/mesh; modem integration, Wi-Fi generation, Armor, guest and Ethernet ports vary.
- Wi-Fi 6 router (high-end, single unit, dual-band)
- A high-end Wi-Fi 6 (AX) router with 2.4/5 GHz (no 6 GHz — that is 6E/7). Wi-Fi 6 speeds need Wi-Fi 6 clients; older devices connect at their generation normally.
- Single router coverage
- Covers a limited area as a single unit; large homes may need mesh/extenders or central placement. A weak room is coverage, not a fault.
- Managed by app or web
- Nighthawk app or web admin. It has no 6 GHz band, so 'no 6 GHz' is the hardware generation, not a fault.
- Symptom boundary
- This record covers NETGEAR Nighthawk RAX120 router when it Ethernet link is limited to 100 Mbps or disconnects. A different symptom on the same hardware, or this symptom on a different NETGEAR product line, has its own record with its own causes and its own cited source.
Stop boundary
When this stops being a self-service repair
Continuing past any one of these costs more than the repair saves — in safety, in warranty, or in evidence a technician needs.
- !Do not force a fixed speed/duplex to mask a bad cable — replace the cable and let the link auto-negotiate cleanly.
Evidence ledger
Sources behind this answer
Visible sources support the visible claims. Home Product Support records the publisher, the fact used and the review date; community reports can suggest an issue but do not become a published fact on their own.
Where the manufacturer's article stops. NETGEAR Support publishes this as "Home networking support". Official NETGEAR router, Orbi, modem, switch and extender support. What that article does not carry is the model boundary — it is written for a product line, and RAX120 is the scope applied here. Where a control label, terminal, indicator pattern or reset sequence differs on your unit, the manual for that exact model is the authority, not this page and not the article.
Exact questions
Common follow-ups
Does the Netgear RAX120 have a 6 GHz band?+
No — the RAX120 is a Wi-Fi 6 (AX) router with 2.4 and 5 GHz bands only. The 6 GHz band came with Wi-Fi 6E (the RAXE models) and Wi-Fi 7. So there is no 6 GHz network to find on this router, which is its generation rather than a fault. It still delivers strong Wi-Fi 6 performance to compatible devices on the 5 GHz band.
My wired connection is slower than my Wi-Fi.+
That almost always means the wired run negotiated a low speed or has a marginal cable. Check the link speed shown on both ends — a gigabit device coming up at 100 Mbps is the tell — then swap in a known-good Cat5e-or-better cable, and try another port. Whichever swap restores full speed identifies the fault: the cable, the port, or the device's own adapter.
Does this answer apply to every NETGEAR model?+
No. It is scoped to RAX120. NETGEAR router/mesh; modem integration, Wi-Fi generation, Armor, guest and Ethernet ports vary.
What should I record before troubleshooting 100 Mbps or Ethernet?+
Record the complete model identifier, exact message or indicator, software/firmware where visible, the operating stage and what still works.
Why is a factory reset not the first step?+
A reset can erase accounts, networks, maps, schedules or preferences without distinguishing 100 Mbps, Ethernet. The ordered checks preserve that evidence.
When should I stop and use qualified service?+
Stop for wet, pinched, hot or damaged cabling/equipment.
Answer for the exact device and software version shown above.