Sometimes the problem isn’t inside your building at all. The internet service provider (ISP) circuit, the provider’s modem or ONT, or the hand-off between their equipment and yours can fail or slow down. This guide helps you work out whether the problem is yours or the provider’s, and what to collect before you call them, so the call is shorter and the fix is faster.
Before you call your provider: write down your account number, circuit ID (if you have one), the exact time the problem started, the lights on the provider’s equipment, and the results of the bypass test below. Providers usually ask for all of these.
Where your network ends and the provider’s begins
→
→
→
→
The demarcation point (demarc) is where the provider’s responsibility ends. Problems before it are theirs to fix; problems after it are usually yours.
Quick first checks
- Check your provider’s outage page or app, and their status line, for known outages in your area.
- Look at the lights on the modem or ONT and compare them with the provider’s guide.
- Restart in order: modem or ONT first, wait until it fully comes up, then your router or firewall.
- Check whether your router’s WAN (internet) port has a public IP address and a gateway.
ONT troubleshooting
An ONT (Optical Network Terminal) is the box that converts the provider’s fiber into Ethernet for your router. Each provider’s ONT has slightly different lights, but these are common:
| Light | What it usually means |
|---|---|
| Power off | No power: check the outlet and the power supply or battery unit |
| LOS (loss of signal) red or flashing | No light arriving from the provider: a cut or disconnected fiber. Call the provider. |
| PON off or flashing | The ONT is not registered on the provider’s network. Call the provider. |
| LAN / Ethernet off | No link to your router: check the cable and the router port |
Don’t unplug, bend or clean the provider’s fiber or open the ONT’s fiber compartment. It belongs to the provider, and the fiber is easily damaged.
ISP circuit down
The key test is the bypass test: connect a laptop directly to the provider’s modem or ONT, bypassing your router or firewall.
- If the laptop gets internet: the circuit is working, and the problem is in your router or firewall (check its WAN settings, logs and recent changes).
- If the laptop gets no internet: the problem is most likely with the provider. Open a ticket.
Note that circuits with a static IP address require you to set the same static IP, gateway and DNS on the laptop for this test. Some providers also lock service to the router’s MAC address; restarting the modem may be needed when swapping devices.
ipconfig /all
ping 8.8.8.8
tracert 8.8.8.8When you open the ticket, give the provider the results, times and lights. Ask for the ticket number and an expected update time.
WAN failover
Many businesses have a second internet connection (often a different provider or a cellular backup) that takes over when the main one fails. Failover problems usually show up only during an outage, when it is too late to test.
- Health checks: the router or firewall must test the main link by pinging a reliable target on the internet, not just by checking whether the port is up. A modem can stay “up” while the internet behind it is down.
- Fail back: check what happens when the main link returns. Some setups need a delay to avoid switching back and forth.
- Port forwards and VPNs: these are tied to a public IP address. On the backup link they need their own settings, or they will stop during failover.
- Test on purpose: schedule a test by unplugging the main link after hours, and confirm that internet, phones and VPNs keep working.
Slow gigabit internet
A “gigabit” plan rarely shows a full 1000 Mbps on a speed test, and that’s normal. Ethernet and internet overhead usually limits real speed tests to around 900 to 940 Mbps over wired gigabit.
- Test with a wired computer that has a gigabit (or faster) network port, plugged straight into the router. Wi-Fi speed tests measure your Wi-Fi, not your plan.
- Check that every link is at 1 Gbps: the computer’s adapter, the switch port, the router’s LAN and WAN ports. A single 100 Mbps link caps the whole path.
- Check the router or firewall: some older or smaller models cannot route or inspect traffic at gigabit speed, especially with security features turned on.
- Test at different times. If speeds are only slow in the evening, the provider’s network may be congested; keep a record of results to show them.
Circuit turn-up
A new business circuit often fails on day one because of a small settings mismatch. Before installation day, get these details from the provider in writing:
- Static IP block or DHCP; for static: usable IPs, subnet mask, gateway, and DNS servers.
- Whether the hand-off is tagged with a VLAN, and the VLAN ID if so.
- Hand-off type and speed: copper Ethernet or fiber, 1G or 10G, and whether a specific SFP is needed.
- Whether auto-negotiation or a fixed speed and duplex is required.
- Whether the modem is in bridge mode or doing routing (NAT) itself.
On the day, test with a laptop first, then connect your router or firewall. Confirm speed, inbound services and failover before the installer leaves.
Demarcation issues
In many offices, the provider’s equipment is in a basement or telecom room, and your equipment is on another floor. The cable between them (sometimes called an extended demarc or inside wiring) can be a gray area for responsibility.
- Find out from the provider and the building who owns the extension cable. Label both ends with the circuit ID.
- If a test at the demarc works but your end doesn’t, the problem is in the extension or your equipment.
- Keep a simple diagram showing where each circuit enters the building and how it reaches your equipment.
How to confirm it’s fixed
- The provider’s equipment lights are normal and the WAN port has the correct IP address.
- A wired speed test shows results in line with your plan, at several times of day.
- A continuous ping to an internet address runs for 15 minutes without drops.
- For failover, a planned test switches to backup and back again without losing key services.
- The provider ticket is closed with a note of what they changed.
Frequently asked questions
How do I know if the problem is my provider or my equipment?
Use the bypass test: connect a laptop directly to the modem or ONT. If that works, the problem is on your side; if not, it is most likely the provider.
Why don’t I get 1000 Mbps on my gigabit plan?
Network overhead limits wired results to roughly 900 to 940 Mbps. Wi-Fi, older computers and slower routers lower it further.
Should I restart the ONT?
Restarting by unplugging its power is generally fine. Don’t disconnect the fiber or reset it to factory settings unless the provider asks you to.
Do I need a backup internet connection?
If your business can’t work without internet, a second connection from a different provider or a cellular backup is worth considering. Test it regularly.
Sources
- FCC: Measuring Broadband America methodology and broadband speed guidance.
- IEEE 802.3 Ethernet standards (framing overhead).
- Provider ONT and modem documentation for light meanings, which vary by provider.
Submit your issue, we can help
Tell us what's happening. We'll reply by email with troubleshooting steps. There's no charge for written guidance.