When everything fails at once, look at what everything shares: power, the modem, the router, and the main switch. Check power and lights in the network closet first. If the internet is working but internal access isn't, a failed switch or a network loop is likely.
Common causes
Power problem in the network closet
A tripped breaker, failed power strip, or dead UPS takes all equipment down.
Internet outage
If only internet access is down but printing and file shares work, it's the provider or modem.
Router failure
If the router fails, nothing gets an address or reaches the internet.
Switch failure
A failed main switch disconnects everything plugged into it.
Network loop
A cable connecting two switch ports together can flood the network and bring it down.
How to fix it, step by step
- 1
Check power in the closet
Confirm the modem, router, and switches have power lights. Check breakers, power strips, and the UPS.
- 2
Check the modem and router
Look at the modem's online light and the router's status lights.
- 3
Restart in order
Restart the modem, then the router, then the switches, waiting for each to come up.
- 4
Look for a loop
If switch lights are all blinking rapidly in sync, unplug recently added cables — especially any cable with both ends in the same switch.
- 5
Isolate the failure
Plug a laptop directly into the router. If it works, the problem is downstream in the switches.
When to call a technician
When the whole office is down, every hour costs money. Call us — we provide on-site emergency network support in Orange County, and we can set up monitoring, battery backup, and failover internet so it doesn't happen again.
On-site support across Orange County · see our business networking and WiFi installation services.
Frequently asked questions
What is a network loop?
It's when cables create a circle between switches or ports, causing traffic to repeat endlessly and overwhelm the network. Business switches can detect and block loops.
Should our network equipment be on a UPS?
Yes. A battery backup keeps the modem, router, and switches running through short power blips and prevents corruption from sudden shutdowns.
How can we prevent office-wide outages?
Business-grade equipment, battery backup, loop protection, labeled cabling, monitoring, and a backup internet connection all reduce the risk.