On this page
01. DHCP changes the IP02. Duplicate address03. Cable and switch04. Power05. PC settings06. Monitor it07. A typical scenario08. Common mistakes09. Quick checklist10. Frequently asked questions
Give the terminal a fixed or reserved IP, check for duplicate addresses, replace the network cable and switch port, fit a UPS, and make sure sleeping PC settings do not drop the connection.
Key takeaways
- Use a fixed or reserved IP.
- Rule out duplicates.
- Replace cables and switch ports.
- Stop the PC sleeping or hibernating.
01DHCP changes the IP
If the terminal gets its IP automatically, a router restart can give it a new one and the software loses it. Set a fixed IP or reserve one in the router. See set the IP.
02Duplicate address
A laptop or phone taking the same IP causes drop-outs. See IP conflict.
03Cable and switch
- Swap the network cable.
- Try another switch port.
- Avoid long cable runs near mains cables.
- Replace cheap switches that hang.
04Power
Brownouts reboot the terminal and drop the link. A small UPS fixes it. See power backup.
05PC settings
- Set the PC to never sleep while attendance runs.
- Let the PC wake on LAN or stay on.
- Disable power saving on the network adapter.
06Monitor it
Run a continuous ping to the device for an hour. Drops in the ping show the network is at fault, not the software.
07A typical scenario
A warehouse terminal dropped every afternoon. A continuous ping showed packets lost when the generator switched on. Moving the switch onto a UPS and replacing the cheap cable solved it.
Illustrative example based on common cases, not a named customer.
08Common mistakes
- Blaming the software first.
- Using Wi-Fi for a fixed terminal.
- Ignoring power quality.
- No fixed IP.
- Cheap unmanaged switches shared with cameras.
09Quick checklist
- Fixed IP
- No duplicates
- Cable and port swapped
- UPS
- PC power settings
- Continuous ping test
10Frequently asked questions
The terminal works but the software shows offline. Why?
The software may not be refreshed, or the Comm Key or port changed. Reconnect and test.
Does Wi-Fi cause this?
Wireless links drop more than cable. Use cable where possible.
Does a bad time zone cause offline?
No. Wrong time affects punches, not connectivity.
Will Qyvea fix it?
Yes, we diagnose network and device issues across Kenya.
This guide is part of our ZKTeco K40 and ZKBio Time.Net series. For the full start-to-finish walkthrough with screenshots, read How to Configure a ZKTeco K40 Pro with ZKBio Time.Net.
ZKTeco and ZKBio are trademarks of ZKTeco Inc. Menu names on the K40 Pro and in the software vary slightly by firmware and software version; where yours differ, look for the nearest match. Qyvea is a ZKTeco reseller and installer in Kenya.
