Is it the internet or the network? 6 steps to find the problem

Why is it necessary to tell them apart first?

When someone at a workplace says the internet is slow, the first reaction is often to call the service provider. The service provider measures the line, says the line is fine, and the problem stays where it was. Or the other way around: a new modem or a new access point is bought, and nothing changes because the problem is in the internet line.

A slowness complaint has three possible sources: the internet line itself, the network inside the workplace, and individual devices. With the right steps, these three can be separated from each other. The steps below do not require technical knowledge; a laptop and a network cable are enough.

Steps 1 and 2: Measure next to the modem with a cable

The first step is to connect a laptop directly to the modem with a network cable. Turn off the wireless network and run a speed test. Repeat the test several times during the day, especially at the hours when the complaints are strongest.

The second step is to compare the result with your subscription speed. If the speed on the wired connection is close to the subscription, your internet line is healthy and the problem is inside. If the speed on the wired connection is also constantly low, or the connection drops from time to time, take a screenshot of the test results and have a fault report opened with the service provider. Having measurements with known times shortens the call.

Expert note: When running the speed test, remember that other devices on the network are also using the internet. If possible, take the measurement once at a quiet hour for the workplace and once at a busy hour; the difference between the two results tells you a lot.

Step 3: Compare the wireless network with the wired network

If the line is sound, using the same laptop at the desk where the complaints come from, connect first wirelessly and then by cable and run a test. If the wired connection is fast and the wireless is slow, the problem is in the wireless network.

Typical causes on a wireless network are: the modem or access point being far away or behind a wall, the same channel being used as neighboring networks, the device being connected to the 2.4 GHz band instead of 5 GHz, and too many devices being loaded onto a single access point. In this case you need to move the access point, fix the channel setting, or add a second access point.

Slowness on the wireless network sometimes comes from just one device. If the wireless card of an old laptop or printer works on an old standard, the access point makes the others wait while it talks to that device. Testing with a different phone at the same desk shows whether the problem is in the network or in the device.

Step 4: Find the device flooding the network

Sometimes the cause of the slowness is not the line or the network but a single device filling up the line on its own. A computer doing a cloud backup, ten computers downloading updates, remotely monitored cameras, or customers watching video on the guest network can use the whole line. Especially on lines with low upload speed, cloud backups and camera monitoring slow down the whole network.

If the modem's or router's interface has a screen showing how much traffic each device uses, look there. If not, turn off the devices you suspect one by one and measure the speed. Once the device causing the problem is found, moving the backup time outside working hours, putting a speed limit on the guest network, or lowering the camera stream resolution is often enough.

Step 5: Check the cable, switch, and port

If the wired connection is also slow at a single desk, the problem is in that desk's cable or in the switch port it is connected to. These problems can be sneaky: there is a connection, but it is slow.

• In the computer's network connection details, check whether the speed shows 100 Mbps instead of 1 Gbps; this is often a sign of a damaged cable or connector.
• Replace the patch cable under the desk with another cable and measure again.
• In the cabinet, plug the same cable into a different port on the switch.
• Look at the switch lights for ports that blink constantly or glow orange.
• Check whether an old switch with 10/100 ports is sitting in the middle of the network.
• Check by hand whether the cabinet is overheating.

Step 6: Check the modem and DNS

Sometimes the speed test gives a good result but pages still open late. The cause is often domain name resolution (DNS); the server your computer asks to find a website's address is answering slowly. Setting a different, reliable DNS server in the router settings can fix this problem.

The modem can also get tired. Home-type modems that have not been turned off for a long time, whose software has not been updated, or that manage many devices on their own slow down over time. If restarting gives temporary relief and the problem returns within a few days, consider using the modem only for the line and managing the network with a separate router.

If no problem is found

Write your measurements on a sheet of paper or in a table: date, time, which device, wired or wireless, download and upload speed. A few days of records reveal a pattern that a single measurement cannot show. For example, slowness that happens at the same time every afternoon points to a backup that starts at that time or to congestion on a neighboring network.

These six steps reveal the source of most slowness complaints. If the problem comes and goes at certain hours, shows up at more than one branch, or there is no management tool showing who is doing what on the network, a measurement that monitors the network for a few days is needed. Desa Bilişim can take these measurements through remote support on the systems it has installed; if you describe your network's structure and the hours when the complaint is strongest, we can decide together where to start.

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