When the network slows down, the router usually takes the blame. Sometimes it deserves it. But in older offices, and in offices that have grown in stages, the problem is often hiding in the walls and ceilings: cabling installed for a different era, a different floor plan or a much smaller team.
Cabling problems are frustrating because they rarely fail cleanly. Instead of going dark, a weak cable run drops packets, renegotiates its connection and slows things down in ways that look like software issues. These are the signs that point toward the physical layer.
1. Some ports connect at 100 Mbps instead of 1 Gbps
Check the link speed on a few computers or on your switch. Gigabit Ethernet needs all four pairs in a cable to work properly. If one pair is damaged or badly terminated, many devices will quietly fall back to 100 Mbps rather than refuse to connect. The user sees a working connection that is a tenth of the speed it should be, and nobody thinks to look at the cable.
2. Problems follow the desk, not the person
If whoever sits at a particular desk complains about dropped calls, slow file transfers or frozen video meetings, swap the laptop. If the problem stays with the desk, look at the wall jack, the patch cord and the run behind it. A cable that was stapled, crushed by furniture or kinked during a renovation can work most of the time and then fail under load.
3. Your switch shows errors on certain ports
Managed switches keep counters for CRC and frame errors. A handful of errors is normal. Steadily climbing numbers on the same ports point to a physical issue such as a bad termination, a damaged run or interference. If your IT provider has never looked at these counters, it is worth asking them to.
4. There are small switches under desks and in cupboards
Unmanaged switches tucked under desks are a sign that the office outgrew its cabling. Someone needed two more ports, there was no free drop, so a switch got added. Over time these chains multiply. Every extra hop is another possible point of failure, and many of these switches end up plugged into whatever outlet happened to be nearby. They also make troubleshooting much harder, because nobody knows exactly what is connected where.
5. Wi-Fi is still poor after new access points
Upgrading to modern access points and seeing little improvement is a classic clue. A Wi-Fi 6 or Wi-Fi 7 access point with a multi-gigabit port is limited by the cable feeding it. If that cable is an older run that was never certified for higher speeds, has been damaged, or stretches beyond the 100-metre Ethernet limit, the access point cannot deliver what it was bought for. Access points powered over Ethernet can also reboot or behave erratically when the run cannot deliver stable power.
Twisted-pair network cable resists interference well, but it is not immune. Runs laid directly across light fixtures, tied to electrical conduit or routed beside motors and elevator equipment can pick up noise that shows up as errors and retransmissions. Good practice keeps data cabling separated from power and supported on its own hooks or trays, rather than lying loose on top of ceiling tiles.
7. The cabling is older than most of your equipment
Cabling installed fifteen or twenty years ago was designed for desktop PCs and desk phones. Today the same network carries video calls, cloud backups, security cameras and wireless traffic from every phone in the building. Older Cat5 or early Cat5e runs may still pass a basic continuity check and struggle with modern loads anyway. If the cabling predates your current lease and nobody has tested it, it is a reasonable suspect.
What to do next
Start with the inexpensive checks. Replace suspect patch cords, look at port speeds and switch error counters, and note which desks or rooms keep having problems. That narrows the field quickly.
If the pattern points to the cable runs themselves, a proper test with a certification tester will show which runs pass and which do not, along with length and signal-loss measurements. That is far cheaper than replacing everything blindly, and it gives you a clear list of what to fix. In many offices the answer is a mix: re-terminate some runs, replace the damaged ones, remove dead cable and add new drops where those under-desk switches were filling the gap.
For businesses weighing a repair against a full upgrade, a walk-through from a team that specialises in network cabling in Toronto can save a lot of guesswork. Installers who work in local commercial buildings every week tend to know how they were wired and where the usual problems hide.
The point is not to rewire the whole office at the first sign of trouble. It is to stop treating the cabling as invisible. When the network is slow and the obvious fixes have not worked, the cable is often the one piece nobody checked.
