How to Troubleshoot Business Network Problems

"The internet's down" is the most common sentence in any IT support queue, and it's almost never a complete description of the problem. Sometimes the internet is fine and one laptop has lost its address. Sometimes the Wi-Fi is fine and the NBN connection box has been unplugged so someone could charge a phone.

Network troubleshooting looks like magic from the outside, but it's really a process of elimination. You start at the bottom of the stack, prove each layer works, and move up until something doesn't. Here's how to do it yourself, in the order an experienced technician would.

Step 1: Work out how big the problem is

Before touching anything, answer one question: who's affected?

• One person: almost certainly that device, its cable, or its Wi-Fi connection.
• A group of people: something they share. Same floor, same switch, same Wi-Fi access point, or the same application.
• Everyone: the router, the internet connection, or something central like DNS.

Also ask what exactly is broken. "Can't get to anything" is a different problem from "email works but the accounting system is slow", which is different again from "Teams calls keep dropping". Write down when it started and what changed just before. A surprising number of network faults begin the same afternoon someone "just moved a few cables".

Step 2: Check the physical layer (yes, really)

It feels too simple, so people skip it. Don't. Look for the obvious first:

• Lights on the equipment. Your router, switches and the NBN connection box all have status lights. A light that's normally green and is now orange, red or off is your biggest clue.
• Cables seated properly. A network cable that's half out of its port can still show a link light but drop packets constantly.
• Power. Check the power board, the power supply and whether a cleaner has borrowed the socket.

Here's a sneaky one worth knowing about. A gigabit network connection uses all four pairs of wires inside a standard network cable. If one pair is damaged, say a cable crushed under a desk leg, the connection often doesn't fail. It quietly drops back to 100 megabits per second, which only needs two pairs. Ten times slower, and nothing tells you. On Windows, open Settings → Network and internet → Ethernet and check the link speed. If a modern PC on a modern switch says 100 Mbps, swap the cable.

Step 3: Does the device have a valid address?

Every device on your network needs an IP address, normally handed out automatically by the router through a service called DHCP. On a Windows PC, open Command Prompt and type ipconfig.

Look at the IPv4 address. If it starts with 169.254, you've found your problem. That's an address Windows invents for itself when it asks for one and nobody answers. It means the device can't reach the DHCP server at all, which points back to the cable, the Wi-Fi connection, or the router.

There's a related fault that catches growing offices out. Most small business networks use an address range with 254 usable addresses. That sounds like plenty, until you count. Twenty staff, each with a laptop, a phone and maybe a tablet, is 60 devices. Add printers, desk phones, cameras, the smart TV in the meeting room and every visitor on the Wi-Fi, and you can hit the ceiling. When the pool runs out, the next device to join simply doesn't get an address. If new connections fail while existing ones work fine, check how many leases your router has handed out.

Step 4: Ping your way outward

Once a device has a proper address, test each hop with ping, which sends a tiny message and times the reply. Work from close to far:

1. Ping your router (the "Default Gateway" address shown in ipconfig). If this fails, the problem is inside your office.
2. Ping a public address by number, such as ping 1.1.1.1. If the router replies but this doesn't, your internet connection is down.
3. Ping a website by name, such as ping microsoft.com. If the number works but the name doesn't, the internet is fine and DNS is broken.

That last distinction saves a lot of time. DNS is the internet's phone book: it turns names into numbers. When DNS fails, everything looks like it's down even though the connection is perfectly healthy. Running ipconfig /flushdns clears out stale entries on that PC; if the whole office is affected, the DNS settings on the router or server are the place to look.

If you get through but things are slow, tracert followed by an address shows every hop along the way and how long each one takes. A sudden jump in time at the first hop outside your building points to the connection, not your network.

Step 5: If the whole office is offline, check the NBN side

When nothing gets out, look at the NBN connection box (the box the NBN installer fitted, separate from your router). Most types have an indicator for the line or optical signal. If that light shows a fault, the problem is upstream of you and no amount of rebooting your router will fix it.

Check your provider's outage page from a mobile phone, then call them with your service details ready. While you wait, a router with automatic 4G or 5G failover is worth its weight in gold. It won't run a busy office at full speed, but it keeps card payments, email and phones alive. If your connection is business-critical, talk to us about business internet with a proper service level and backup link.

Step 6: Wi-Fi problems are usually physics problems

Wi-Fi complaints tend to be "it's slow" or "it drops out in the back room". Both usually come down to radio physics:

• Distance and walls. Wi-Fi signal falls off quickly with distance, and brick, concrete, metal and even water (fish tanks, people) absorb it. One access point in the front office won't cover the warehouse.
• The 2.4 GHz band is crowded. It travels further but has only three non-overlapping channels, and every neighbouring business is shouting on them too. The 5 GHz and 6 GHz bands are faster and less congested but don't pass through walls as well.
• Interference. Microwaves operate in the 2.4 GHz range. If the Wi-Fi in the lunchroom gets worse at 12:30, you're not imagining it.

The fix for poor coverage is more access points, properly placed and managed as one system, not a cheap range extender, which typically halves the speed of everything it relays. Voice calls are especially sensitive to Wi-Fi problems; our VoIP setup tips explain why.

Step 7: When it's slow, find out who's using the bandwidth

Do the maths on a typical NBN business plan with 40 Mbps of upload. One person syncing a 4 GB video folder to OneDrive uses 32,000 megabits. At 40 Mbps that's 800 seconds, about 13 minutes during which the upload pipe is completely full. Everyone else's video calls stutter, and the person syncing has no idea they're the cause.

Most business routers can show which device is using the most traffic. Common culprits are cloud backups running during business hours, large file syncs, and Windows updates downloading on twenty PCs at once. Schedule the heavy stuff after hours and set quality-of-service rules so calls get priority.

Step 8: Don't forget security

A network that's suddenly slow for no obvious reason can also be a sign of something worse: a compromised device sending data out, or malware spreading between machines. If you can't explain unusual traffic, treat it as a security question, not just a performance one. Our article on whether your network is properly locked down covers the basics.

Write it down for next time

Every network fault you fix teaches you something about your network. Keep a simple log: what broke, what the symptoms were, and what fixed it. Add a diagram showing where the router, switches and access points are and how they connect. The next person to troubleshoot, possibly you at 7:45 on a Monday, will be very grateful.

And if the network keeps throwing up the same problems, that's a sign it needs proper monitoring rather than more troubleshooting. With managed IT, we watch your equipment and often fix the fault before anyone in the office notices.

Frequently asked questions

Why is my internet connected but not working?

Usually DNS or an address problem. If ipconfig shows an address starting with 169.254, the device can't reach your router. If you can ping 1.1.1.1 but not a website name, DNS has failed. If neither works but the router responds, your internet connection itself is down.

How do I tell if the problem is my network or my NBN connection?

Ping your router first. If it responds, your internal network is working. Then ping a public address like 1.1.1.1. If that fails, check the lights on the NBN connection box and your provider's outage page, because the fault is outside your office.

Why is our office Wi-Fi so slow?

The most common causes are too few access points for the space, congestion on the crowded 2.4 GHz band, walls and metal blocking signal, and one or two devices using all the bandwidth for backups or file syncs. A wired speed test tells you whether it's the Wi-Fi or the internet connection.

Does restarting the router actually fix anything?

Often, yes. A restart clears the router's memory, renews its connection to your provider and resets stuck sessions. But if you're restarting it weekly, something underneath is wrong, such as overheating, outdated firmware or an overloaded device, and it needs proper diagnosis.

Local IT and cyber security support across NSW

Chewing IT runs managed IT and cyber security for small and mid-sized businesses from our Wyong and Hornsby offices, covering the Central Coast, Newcastle, Lake Macquarie and Hornsby.

Tired of network dropouts? Talk to our team about monitoring and support that finds the fault before your staff do.