Slow office internet is usually caused by one of five things: an ISP issue, overloaded network hardware, Wi-Fi interference, bandwidth hogs, or DNS problems. The mistake most people make is guessing at the cause and throwing money at a faster plan when the real problem might be a $200 router that needs replacing or a backup job running during business hours.
This guide walks through each potential cause in order, starting with the quickest checks and working toward the less obvious culprits. Follow the steps in sequence; each one either eliminates a cause or points you to the fix.
Step 1: Test Your Actual Speed
Before you can troubleshoot, you need a baseline. Run a speed test from a computer that is connected directly to your router with an Ethernet cable, not over Wi-Fi. This is important because Wi-Fi adds its own variables, and you need to isolate whether the problem is your internet connection or your wireless network.
Open a browser and go to speedtest.net or fast.com. Run the test and write down three numbers: download speed, upload speed, and ping (latency). Run the test two or three times to get a consistent reading.
Now compare those numbers to what your ISP plan promises. If your plan is 250 Mbps download and your wired test shows 240 Mbps, your internet connection is fine and the problem is almost certainly on your internal network (Wi-Fi, router, or congestion). If your wired test shows 80 Mbps on a 250 Mbps plan, the problem is either your ISP, your modem, or the cable between your modem and router.
Write down the results. You will need them if you call your ISP or if you want to compare before and after making changes.
Step 2: Check for ISP Issues
If your wired speed test came back significantly below what your plan promises, the problem may be on your ISP's side.
Start by visiting your ISP's status page. Most ISPs have an outage map or service status page you can check online. Search for "[your ISP name] outage map" to find it. If there is a known outage or congestion in your area, you may just need to wait.
If there is no reported outage, restart your modem. Unplug the power cable from the modem (not the router, the modem specifically), wait 30 seconds, and plug it back in. Wait two to three minutes for the modem to fully reconnect to your ISP. If your modem and router are the same device (a combo unit from your ISP), this restart resets both.
After the modem restarts, run the wired speed test again. If speeds are still well below your plan, check the modem's indicator lights. A solid green or blue light on the "online" or "internet" indicator usually means the connection is healthy. A flashing or red light on those indicators often signals a problem. The exact meaning varies by model, so check your modem's manual or search for the model number online.
If wired speeds remain low after a modem restart and there is no reported outage, call your ISP. Tell them you have tested on a wired connection, restarted the modem, and are getting X Mbps on a plan that should deliver Y Mbps. Giving them these specifics will help them diagnose the issue faster and prevents them from running you through basic troubleshooting you have already done.
Step 3: Check Your Router and Network Hardware
If your wired speed test matched your ISP plan but the office still feels slow, the problem is likely your router or internal network equipment.
Ask yourself a few questions about your router. How old is it? Consumer routers older than three to four years often cannot handle the demands of a modern office. Is it a consumer model from a retail store? Consumer routers are designed for a household with five to ten devices; an office with 15 to 30 devices (computers, phones, printers, smart devices) can overwhelm one quickly.
Restart the router by unplugging its power, waiting 30 seconds, and plugging it back in. Wait two minutes for it to fully boot. If your router is separate from your modem, you only need to restart the router at this step.
Check for firmware updates on your router. Log in to the admin interface (typically at 192.168.1.1 or 192.168.0.1 in your browser), navigate to the System, Administration, or Firmware section, and check for available updates. Outdated firmware can cause performance issues and security vulnerabilities.
Look at how many devices are connected. Most router admin interfaces show a list of connected devices. If you see 25 devices connected to a consumer router rated for 15, that is your bottleneck. Signs that your router is the problem include periodic connection drops, slowdowns that happen at the same time every day (when everyone is online), and devices failing to connect to Wi-Fi even though the network appears available.
If your router is a consumer model and you have more than ten employees, replacing it with a business-grade router or firewall is the most impactful upgrade you can make. Business-grade hardware from Ubiquiti, Meraki, FortiGate, or SonicWall is designed to handle dozens of concurrent devices without degradation.
Step 4: Diagnose Wi-Fi Specific Issues
Wi-Fi is almost always slower than a wired Ethernet connection, and some speed reduction is normal. The question is how much speed you are losing over Wi-Fi compared to wired.
Run a speed test over Wi-Fi from the same location where you tested wired. If your wired test showed 250 Mbps but Wi-Fi shows 40 Mbps, you have a significant Wi-Fi problem. If Wi-Fi shows 180 Mbps, that is a normal and acceptable reduction.
The most common causes of poor Wi-Fi performance are distance from the access point, physical obstructions (walls, metal filing cabinets, concrete), and interference from other wireless networks nearby.
Download a free Wi-Fi analyzer app on your phone (Wi-Fi Analyzer on Android, or use the built-in wireless diagnostics on Mac). These tools show you which Wi-Fi channels are congested in your area. If your router is on the same channel as five other nearby networks, switching to a less crowded channel can improve performance noticeably.
Your router broadcasts on two frequency bands: 2.4 GHz and 5 GHz. The 5 GHz band is faster but has a shorter range and does not penetrate walls as well. The 2.4 GHz band reaches farther but is slower and more susceptible to interference. For desks close to the router, connect to 5 GHz. For areas farther away, 2.4 GHz may be the only option, but performance will be lower.
If your office is larger than about 1,500 square feet, a single access point probably cannot cover the entire space adequately. Consider adding additional access points or switching to a mesh Wi-Fi system designed for business use. Placing a second access point in the area with the weakest signal can make a dramatic difference.
Step 5: Identify Bandwidth Hogs
Sometimes the internet connection and network hardware are both fine, but a specific device or application is consuming most of the available bandwidth.
Common culprits include cloud backup services running during business hours, Windows updates downloading simultaneously on every computer in the office, employees streaming music or video, and large file transfers to or from cloud storage.
To identify the offender, log in to your router's admin interface and look for a section labeled Traffic Monitor, Bandwidth Usage, Connected Devices, or Statistics. Most business-grade routers show per-device bandwidth consumption in real time. If you see a single device using 50 percent of your bandwidth, you have found the problem.
The fixes are straightforward. Schedule large backups and updates to run after business hours. Configure Windows Update policies to download updates overnight rather than during the workday. If your devices are managed through Microsoft Intune, you can set delivery optimization policies that control when and how updates are downloaded, preventing every machine from pulling the same update simultaneously and flooding your connection.
Set up Quality of Service (QoS) rules on your router to prioritize business-critical traffic. QoS tells the router to give priority to applications like Microsoft Teams, VoIP phone calls, and cloud business applications over less critical traffic like software updates and streaming. Look for QoS settings in your router's admin interface under Traffic Management, QoS, or Bandwidth Management.
For ongoing visibility into what is consuming your network resources, a monitoring dashboard makes a real difference. The Athencia One Portal provides real-time visibility into network health and device status, so you can spot bandwidth problems before your team starts complaining about slow internet.
Step 6: Check DNS Settings
If websites feel slow to load even though speed tests look normal, your DNS server may be the problem. DNS is the system that translates website names (like athencia.com) into IP addresses. A slow or unreliable DNS server adds a delay to every website you visit, every cloud application you open, and every link you click.
By default, your network uses your ISP's DNS servers, which are not always fast. Switching to a faster public DNS service can make web browsing feel noticeably snappier.
To change your DNS settings at the router level (so all devices on the network benefit), log in to your router's admin interface and look for DNS settings under WAN, Internet, or Network settings. Replace your ISP's DNS addresses with one of these options:
- Cloudflare: 1.1.1.1 and 1.0.0.1 (fast and privacy-focused)
- Google: 8.8.8.8 and 8.8.4.4 (reliable, widely used)
- Quad9: 9.9.9.9 and 149.112.112.112 (includes built-in malware blocking)
Save the settings and restart your router. Every device on the network will now use the new DNS servers automatically.
If you want DNS-level security that also blocks malicious and phishing websites, consider Cloudflare's malware-blocking DNS (1.1.1.2) or a dedicated DNS filtering service. See our guide on DNS filtering for more on that approach.
When to Upgrade Your Internet Plan
If you have worked through all the steps above and your connection is legitimately maxed out, it may be time for a faster plan. Here are the signs:
Your wired speed tests consistently match your ISP plan, which means you are getting what you are paying for, but it is not enough. Your plan is under 100 Mbps and you have more than ten employees. Video calls are choppy even on wired connections. Multiple people report slowdowns at the same time during normal business activity.
As a general rule, plan for 10 to 25 Mbps per employee for typical office work that includes video conferencing, and consider a plan upgrade before you hit that ceiling rather than after.
Need Help?
If you have worked through these steps and your office internet is still slow, there may be a deeper issue with your network configuration or hardware. Contact Athencia for a thorough network assessment. We will pinpoint the problem and get your team back to full speed.
