No link light at the switch
No link light at the switch
Symptom
You terminated the cable and plugged it into the PoE switch (or PoE injector), but the switch port link LED stays off. The camera or gateway does not power up.
Likely causes
- Bad patch cable or miswired termination (split pair, reversed A/B).
- Switch port disabled, in the wrong VLAN, or already exceeding PoE budget.
- PoE injector PSU failed or injector wired data-in/PoE-out backwards.
- Damaged RJ45 connector (bent pin, loose crimp, pushed-out lock tab).
Fix
If you suspect the cable
- Test the run with a cable meter. Confirm continuity on all 4 pairs and correct T568B pin-out.
- If wiremap fails, re-terminate the suspect end. Keep untwist under 13 mm.
- Swap in a known-good patch cable at each end to isolate the run from the patches.
If you suspect the switch port
- Move the cable to a different port known to have PoE and a link.
- In the switch management UI, confirm the port is enabled, untagged on the correct VLAN, and PoE on.
- Check the PoE budget. If total draw exceeds the switch budget, see Camera reboots every few minutes.
If you suspect the injector
- Verify the PSU LED is on. Measure DC output at the barrel jack.
- Confirm Data In goes to the switch and PoE Out goes to the camera. Injectors fail silently when reversed.
- Swap the injector with a known-good unit.
If you suspect the connector
- Inspect both RJ45 ends under light. Re-seat fully until the lock clicks.
- Re-crimp any connector with a bent pin or loose jacket.
Verify
- Switch port link LED turns solid green or amber within 5 seconds of plugging in.
- Switch management UI shows the port as Up at 100 or 1000 Mb/s.
- Camera or gateway boots (status LED changes from off to solid/blinking).
If none of this worked
- Capture the switch port stats: interface counters, PoE class, negotiated speed.
- Photograph both RJ45 terminations and attach to the support ticket.
- See also: Camera reboots every few minutes.