An access point's Ethernet link is its lifeline, and Ubiquiti's guidance is to check the link speed first. The port LED on the switch is green for 1000 Mbps and amber for 10 or 100 Mbps, flashing for activity, so an AP on an amber port is on a slow cable or a bad pair. Replace the cable, since damaged cables are among the most common faults, and try another switch port or PoE adapter to rule out port damage.
The checks in more detail
A U7 Pro can use a 2.5 GbE uplink for its higher speeds, so check that its port and the switch port both support the speed, and use a cable rated for it. A U6 Pro uses gigabit. If the AP is powered by PoE and the budget is short, devices can restart or drop, so check the switch's PoE budget. Watch the AP's LED: blue and flashing off every five seconds means the AP lost network connectivity and is searching for a wireless uplink, which is slower than wired, so restore the cable.
Check for a network loop and for the wrong VLAN tagging on the AP's switch port, which can leave the AP with the fallback address 192.168.1.20 or none. If the link drops to 100 Mbps, unplug and replug to renegotiate. Test the cable with a laptop before installing it in a ceiling. Test each AP cable before it goes into the ceiling, with a laptop and a known-good switch port, and label both ends.
A cable that tests fine flat on a bench can fail once pulled through a bend, so retest after installation. If an AP negotiates at 100 Mbps, replace the patch cable first, then the run, and keep a record of which AP is on which switch port. Use a PoE tester or a switch's port information to confirm the AP is getting the power class it needs, since an AP starved of power can also negotiate poorly.
Differential
Likely causes of “Ubiquiti UniFi access points Ethernet link is limited to 100 Mbps or disconnects”, and how to tell them apart
- 1
A bad cable
What separates it The port light on the switch is amber because the cable is bad
How to confirm Replace the cable, and check whether the port light turns green
- 2
An under-rated cable or port
What separates it The 2.5 GbE speed is not reached because the cable or the port is not rated for it
How to confirm Use a cable and a port that are rated for 2.5 GbE, such as Cat6 or better
- 3
PoE budget short
What separates it The access point restarts or drops because the switch does not have enough PoE budget
How to confirm Check the PoE budget of the switch, and make sure that it can power all of its devices
- 4
A lost uplink
What separates it The access point is searching for a wireless uplink because it has lost its wired link
How to confirm Restore the wired link, by checking the cable, the port and the switch
- 5
Wrong VLAN tagging
What separates it The access point falls back to its fallback address because of wrong VLAN tagging
How to confirm Fix the port tagging on the switch, so the access point gets an address on the right network
Before you touch a setting
Record this first — changing settings destroys the evidence
- The color of the port light on the switch
- The type of cable that connects the access point
- The PoE budget on the switch and what it is using
- The IP address that the access point shows
Try in this order
0 of 7 completedRead the port LED
ReversibleRead the port light, since green means a link at 1000 Mbps and amber means 10 or 100 Mbps.
Replace the cable
ReversibleReplace the cable and test it, since a bad cable is the most common cause of a slow link.
Try another port
ReversibleTry another port on the switch, or use a PoE adapter, to rule out a fault with the port.
Check PoE budget
ReversibleCheck the PoE budget on the switch, to see that it has enough power to spare.
Check the AP LED
ReversibleCheck the light on the access point, since it shows the state of its uplink.
Check tagging
ReversibleCheck the tagging and the IP address that the access point has received, and then test again to see whether it helped.
Replug
ReversibleReplug the cable at both ends, so that the two devices negotiate the link speed again.
Model-specific
What is true of this model and not of its siblings
- U7 Pro
- The U7 Pro supports a 2.5 GbE PoE uplink.
- U6 Pro
- The U6 Pro has a gigabit port.
Stop boundary
When this stops being a self-service repair
- !If a good cable and port stay amber, RMA the switch or AP under warranty
- !If the AP is stuck on the fallback address, fix tagging
- !If PoE is short, move to a bigger switch or an injector
Evidence ledger
Sources behind this answer
White, blue and port LEDs.
Cables, ports and RMA.
LED states, IP address checks and TCP 8080.
The company and its products.
Exact questions
Common questions
What does an amber port LED mean?+
An amber port light means a link at only 10 or 100 Mbps.
What does the AP LED show when it loses its uplink?+
When it loses its uplink, the light flashes blue and off every five seconds.
What is the fallback IP?+
The fallback IP address is 192.168.1.20, which the access point uses when it gets no address.
Can PoE budget matter?+
Yes, a short PoE budget can cause restarts, as the access point does not get enough power.
Does the U7 Pro use 2.5 GbE?+
Yes, the U7 Pro can use a 2.5 GbE uplink, if the cable and the switch port support it.
Should I replace the cable?+
Yes, replace the cable first, since it is the cheapest thing to check.
Can a loop cause it?+
Yes, a loop in the cabling can cause slow or failing traffic.
Can tagging matter?+
Yes, wrong tagging can leave the access point without a proper address.
How do I test a cable?+
Test a cable with a laptop before you install it, to check its speed.