Troubleshooting ideas for frequent disconnections of network cameras

Troubleshooting order

First floor: power supply

• Insufficient PoE power supply: The distance is too long, the wire diameter is too thin, and the non-oxygen-free copper wire causes excessive voltage drop. The device restarts when it is at high power (infrared is on, dome heating, pan/tilt rotation). Use a multimeter to measure the terminal voltage.
• The total power of the switch is insufficient: The total power of the access device exceeds the PoE budget. It manifests as multiple devices being disconnected at the same time or randomly.
• Aging of the power adapter: The output voltage drops and the load capacity becomes worse.

Layer 2: Physical link

• The crystal head of the network cable is oxidized, the crimping is not strong, and the wiring sequence is wrong.
• Cables are squeezed, bent excessively, or bitten by rats.
• Water has entered the outdoor joint and the waterproofing treatment is not in place.
• The optical fiber transceiver or optical module is faulty, and the pigtail is bent.

The third layer: network configuration

• IP address conflict: Two devices have the same IP address and appear to be on and off. Check with a scan tool.
• Switch port problem: Port negotiation abnormality, STP convergence leading to temporary interruption.
• ARP attack or broadcast storm: There are loops or abnormal devices in the network.
• VLAN/subnet configuration error: Cross-network segment access is blocked.
• DHCP lease issue: The camera uses DHCP but the lease is too short or the address pool is exhausted.

The fourth layer: the device itself

• Firmware defect may be solved after upgrading.
• The equipment is overheated (especially outdoor equipment boxes in summer), check the heat dissipation.
• Hardware failure requires repair or replacement.

Quick positioning method

1. Look at the rules: Fixed-time disconnections are mostly related to temperature, power supply, and scheduled tasks; random disconnections are mostly related to the network and poor contact; multiple simultaneous disconnections point to the switch or power supply.
2. Ping test: Continuously ping the camera IP, and count the packet loss rate and interruption time.
3. Replacement method: Change the port, change the network cable, change the power supply, and eliminate them one by one.
4. Read logs: The system logs of NVR and cameras often record the reasons for restarts.
5. Packet capture analysis: For difficult problems, you can capture packets through switch port mirroring.

Preventive measures

• Use fixed IPs for key points and keep address ledgers.
• Choose an industrial-grade PoE switch with sufficient power and leave a 20% power margin.
• All outdoor joints are waterproofed.
• The equipment box should be well dissipated and insect-proof.
• Connect to UPS to avoid repeated restarts caused by instantaneous power outages.