Updated October 2026 · For office managers and IT teams
If file transfers across your office network crawl along at about 11 MB per second, your LAN is probably running at 100 Mbps. Most modern equipment supports gigabit (1,000 Mbps), so the fix is usually simple once you find the weak link.
Here is how to get your local network from 100 Mbps to a full gigabit.
- A LAN runs only as fast as its slowest cable, port or device.
- Cat5e or Cat6 cable and gigabit switches are required for 1 Gbps.
- Adapter settings forced to 100 Mbps are a common hidden cause.
- Faster LAN speed helps local transfers; internet speed depends on your plan.
Find the Bottleneck
- Check each computer’s link speed (Windows: Settings → Network & internet → Ethernet).
- Look at switch port lights; many switches show a different color for 100 Mbps.
- Inspect wall jacks and patch panels, which are often older than the rest of the network.
Upgrade Cabling and Switches
| Component | Needed for 1 Gbps |
|---|---|
| Cable | Cat5e or Cat6 (Cat6 preferred for new runs) |
| Switch | Gigabit switch (10/100/1000) |
| Router LAN ports | Gigabit ports |
| Network adapter | Gigabit Ethernet adapter |
Check Adapter Settings
- Open Device Manager and expand Network adapters.
- Right-click the Ethernet adapter → Properties → Advanced.
- Set Speed & Duplex to Auto Negotiation.
- Update the adapter driver if the option is missing.
Why LANs Get Stuck at 100 Mbps
Most offices grow in stages. A few cables are older than the rest, an old switch survives in a closet, or a wall jack was punched down with a broken pair. Gigabit Ethernet needs all four wire pairs in a cable; if one pair is damaged, the connection quietly falls back to 100 Mbps, which only uses two pairs. That is why a network can look fine but perform at one tenth of its potential.
Test Each Link Methodically
- List every device, switch and patch point between the user and the router.
- Check the negotiated speed at the computer and at the switch port.
- Swap in a known-good patch cable to rule out cable damage.
- If a wall jack is involved, use a cable tester to check all four pairs.
- Replace any 10/100 switches or adapters you find.
Beyond 1 Gbps
If your team moves large files, works with video or runs network storage, consider multi-gigabit switches and adapters (2.5, 5 or 10 Gbps) on key links. Pair a faster LAN with a faster internet connection so cloud work keeps up.
Cronus can assess your office network, recommend upgrades and connect you with fixed wireless or dedicated fiber sized for your team.
When LAN Speed Is Not the Problem
If your LAN shows 1 Gbps but internet is still slow, your internet plan or provider is the limit. Cronus offers fixed wireless and dedicated fiber with symmetrical speeds up to multi-gigabit, plus managed Wi-Fi and network design for offices.
Need a faster office network?
Cronus designs and installs business networks and internet in Detroit.
Frequently Asked Questions
Can Cat5 cable do 1 Gbps?
Original Cat5 is unreliable at gigabit speeds. Use Cat5e or Cat6 for 1 Gbps.
Why does my switch show 100 Mbps?
The connected device, cable or the switch port itself may only support 100 Mbps, or the adapter may be set to 100 Mbps manually.
Will gigabit LAN speed up my internet?
Only if your internet plan is faster than 100 Mbps. Otherwise the internet plan remains the limit.
