Slow Network? How to Tell If It's Your ISP or Your Own Wiring

When the internet crawls, the reflex is to call the ISP and buy a bigger package. Sometimes that fixes it. Often it changes nothing, because the bandwidth was never the problem. We get called out to "slow internet" jobs regularly, and more than half of them turn out to be the wiring, the switch, or the Wi-Fi inside the building, not the line coming in. Upgrading the plan on those sites just costs more for the same speed.

Before you spend a shilling, you can find out which side the problem is on. It takes about ten minutes.

The one test that splits the problem in two

Take a laptop and a network cable. Plug directly into the router or ONT your ISP installed, right at the box, and run a speed test. Then plug into the wall port at a normal desk and run it again. Then disconnect the cable and test over Wi-Fi from where staff actually sit.

• Slow even plugged into the box: the problem is upstream. Now it is fair to call your ISP.
• Full speed at the box, slow at the desk: the drop is in your cabling or switches.
• Fine on cable, bad on Wi-Fi: your wireless coverage is the bottleneck, not the internet at all.

That single comparison tells you who to call and stops you paying to fix the wrong thing.

The culprits we find inside the building

When the problem is internal, it is usually one of these, roughly in the order we run into them:

A 10/100 switch choking a gigabit line. This is the most common one. Your ISP delivers, say, 200 Mbps, but a cheap old switch in the cabinet caps every port at 100 Mbps, and if it is oversubscribed it delivers far less. The line is fine. The KES 2,000 switch someone bought years ago is the ceiling. A gigabit switch fixes it for less than a month of a bigger internet plan.

Cat5 or badly terminated cabling. Old Cat5 (not Cat5e) tops out low, and a single kinked run, a bad crimp, or a cable run next to a power line can drag a connection down or make it drop intermittently. One bad patch cable can make a whole desk look cursed.

One consumer router trying to cover a whole floor. The all-in-one box from Safaricom, Zuku, or Faiba is built for a home. Put 25 devices, a POS, and cameras on it across an office and the Wi-Fi thins out past the first two rooms. That is not a fault, it is the wrong tool. Proper coverage means access points placed for the space, not one router in a corner.

2.4GHz congestion. In a building full of other businesses, the 2.4GHz band is a traffic jam of overlapping networks. Devices that could use the cleaner, faster 5GHz band often sit on 2.4GHz because nobody configured otherwise. This alone can halve real-world speed.

Everything on one flat network. Guests streaming video, staff laptops, the POS, and CCTV all sharing one network means they fight for the same pipe, and a single heavy user drags everyone down. Separating them (a guest network, and the POS and cameras on their own segment) fixes both speed and security at once.

When more bandwidth genuinely helps

Sometimes the line really is the limit: many people on video calls at once, large uploads to the cloud, or a backup running during the day on a small plan. If the box-level speed test comes back slow, or you have outgrown a contended home-grade plan, a bigger or business-grade line is the right spend. The point is not that ISPs are never the issue. It is that you should know before you pay.

One thing worth checking with your provider: whether your plan is contended (shared with other customers) and what the contention ratio is. A cheap shared plan can test full at 6am and crawl at 11am for reasons no amount of internal fixing will solve.

What a fix usually looks like

Rarely a rip-and-replace. More often it is one switch swapped for gigabit, a couple of access points placed properly, a few cable runs re-terminated, and the network split so the POS and cameras stop competing with guest Wi-Fi. We assess what you have, prove where the loss is with the same test above, and change only the part that is actually holding you back.