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Troubleshooting Guide By Alex Morgan · March 2026 · 8 min read

Business Broadband Running Slow? Complete Troubleshooting Guide

Before calling your ISP, run through this guide. Most business broadband issues are solvable in under 30 minutes if you know what to check.

🔌 Step 1: Is It a Full Outage or Just Slow?

The diagnosis approach is different depending on the symptom:

SymptomLikely CauseFirst Check
Completely no internetRouter, line fault or ISP outageCheck ISP status page first
Slow but workingCongestion, router issue, or line degradationRun speed test at router
Intermittent dropsLine fault, router overheating, or ISP routingCheck router logs
Slow on WiFi onlyWiFi interference or router placementTest with ethernet cable
One device affectedDevice network settingsRestart that device

📊 Step 2: Check Your ISP Status First

Before spending an hour diagnosing your own equipment, check your ISP's service status page. Most major outages are listed within 15–30 minutes of occurrence. Also check DownDetector.co.uk for real-time user reports.

🌐 Step 3: Router Checks

  • Power cycle: Unplug the router for 60 seconds (not just restart — physically unplug). This clears memory and often fixes intermittent issues.
  • Check for overheating: Routers in cupboards or against walls can overheat and throttle performance. Check the router is ventilated.
  • Check WAN port lights: The WAN/Internet LED should be solid green. If it's red or off, the issue is between the router and the line — not your internal network.
  • Log into router admin: Check the WAN connection status page for any error codes — these often identify the exact fault.

🔍 Step 4: Distinguish a Line Fault from a Router Fault

Connect a laptop directly to the router via ethernet cable. If the internet is still down or slow, the issue is the line or ISP side (not your WiFi or internal network). If it's faster via ethernet, the issue is your WiFi setup.

For FTTP connections: check the ONT (Optical Network Terminal — the white box installed by the engineer). The PON light should be solid green. If it's flashing or off, there's a fault on the fibre line that requires an engineer.

📞 Step 5: When to Call Your ISP

  • You've checked the ISP status page and there's no known outage
  • The router shows a WAN connection error that hasn't resolved after 30 minutes
  • The ONT shows a fibre fault (PON light not solid)
  • Speed is consistently below 50% of your contracted speed for more than 24 hours
  • Intermittent drops are happening more than 3 times per day

⚠️ Document before you call

Before calling your ISP, note: what time the issue started, what the speed test shows (at-router ethernet, not WiFi), and any error lights on the router. This speeds up diagnosis significantly and reduces the chance of an unnecessary engineer visit charge.

🛡️ Step 6: Implement Failover So This Never Matters

The best solution to broadband problems is making sure they don't interrupt your business. A 4G failover connection (like Telexico's Assure-X) automatically switches your business to 4G within 30 seconds of your main line failing — without any manual intervention. Monthly cost: £15–£30. Cost of a day's downtime: typically £2,000–£10,000.

Add 4G failover to your existing broadband connection — automatic switchover, no manual action needed.

Add Broadband Failover →