Why Your 10 Gig Speed Test Only Shows 1-2 Gbps (And How to Fix It)

Why Your 10 Gig Speed Test Only Shows 1-2 Gbps (And How to Fix It)

You upgraded to 10 Gig fiber, ran a speed test, and got 940 Mbps. Or maybe 1.8 Gbps. It's one of the most common complaints after a 10 Gig install, and in almost every case the circuit is fine. The bottleneck is somewhere between the carrier's equipment and the computer running the test.

A 10 Gbps connection is only as fast as the slowest piece of equipment in its path. Here are the usual culprits, in the order we find them, and what it takes to fix each one.

1. Your Firewall Can't Keep Up

The firewall is the most common bottleneck on a new 10 Gig circuit. Many business firewalls have 1 Gbps ports on the internet side, and even firewalls with 10 Gbps ports often can't inspect traffic that fast.

Watch the spec sheet closely. Firewall vendors usually advertise "firewall throughput," which measures basic traffic with security features turned off. Once you turn on intrusion prevention, malware scanning, and SSL inspection (the features you're paying for), real throughput is often much lower than the headline number. Most vendors publish a separate "threat protection" figure on the same spec sheet, and that's the one to compare against your 10 Gbps circuit.

The fix: size the firewall by its "threat protection" or "NGFW" throughput, not its headline number. Our post on next-generation vs. traditional firewalls explains what those features do, and Managed Firewall can size, install, and run one built for 10 Gig.

2. Your Switch Ports Are 1 Gig

Most office switches have 1 Gbps ports. If traffic passes through any 1 Gig port between the firewall and your computer, that's your ceiling. Watch the uplinks too: a switch with 10 Gig ports for servers but a 1 Gig link back to the core will still cap everyone behind it.

The fix: use switches with 10GbE ports (or SFP+ fiber ports) on the firewall connection, on uplinks between switches, and on servers and workstations that need full speed. Desktop users who just browse and email don't need 10 Gig ports, so you only upgrade where it matters. See Managed Switch.

3. Your Cabling Wasn't Built for 10 Gbps

Network cable has speed limits that depend on its category and length:

• Cat5e: rated for 1 Gbps. Not suitable for 10 Gig.
• Cat6: supports 10 Gbps only on shorter runs, up to about 55 meters (180 feet).
• Cat6A: supports 10 Gbps up to the full 100 meters (328 feet).
• Fiber: supports 10 Gbps and beyond over much longer distances. Best for links between closets and floors.

A bad patch cable, a damaged run, or a poorly terminated jack can also force a link down to 1 Gbps without anyone noticing.

The fix: have the runs that need 10 Gbps tested and certified, and replace what doesn't pass. Our network cabling team can test existing runs and install Cat6A or fiber where needed.

4. The Computer Running the Test Has a 1 Gig Network Card

Nearly every laptop and most desktops ship with a 1 Gbps Ethernet port, and many laptops have no Ethernet port at all. If the test computer has a 1 Gig network card, 940 Mbps is the most it can ever show, no matter how fast the circuit is.

The fix: test from a machine with a 10GbE network card (a PCIe card or a Thunderbolt 10GbE adapter works) plugged directly into a 10 Gig switch port.

5. You're Testing Over Wi-Fi

Wi-Fi can't show you what a 10 Gig circuit can do. Even with the latest access points, a single laptop on Wi-Fi typically sees well under 2 Gbps in real conditions, and often much less with walls, distance, and other users. Wi-Fi is great for everyday work, but it's the wrong tool for testing a 10 Gig line.

The fix: always test 10 Gig over a wired connection. To give wireless users more speed, make sure your access points have multi-gig uplinks. See Managed WiFi.

6. The Speed Test Itself Is the Limit

Browser speed tests weren't designed for 10 Gbps. The test server may not have enough capacity, your browser may not be able to process data that fast, and a single connection over long distances is limited by latency. Testing to a server across the country will almost always show lower results than one nearby.

The fix: pick a test server close to you that supports multi-gig speeds, and use a test that opens multiple connections at once. For an accurate number, network engineers use tools like iperf3 to test against a known 10 Gig server. Your provider can run a test from their equipment to confirm the circuit is delivering what you're paying for.

7. Storage and Applications Can't Fill the Pipe

Even once the network is fixed, real file transfers may not hit 10 Gbps. Filling a 10 Gig connection means reading or writing about 1.25 GB per second, which is faster than many hard drives and some network storage systems can handle. Some applications and cloud services also limit how fast a single transfer can go.

The fix: use fast SSD or NVMe storage on systems that move large files, and use transfer tools that send data in parallel. Many workflows get full value from 10 Gig because many users and transfers share it at once, not because one file moves at 10 Gbps.

How to Test a 10 Gig Circuit Properly

• Use a computer with a 10GbE network card.
• Plug it into a 10 Gig switch port, or directly into the firewall's LAN port, with Cat6A or fiber.
• Close other heavy applications and backups during the test.
• Pick a nearby, multi-gig test server, or use iperf3 to a known 10 Gig endpoint.
• Test several times and at different times of day.
• If results are still low, test from the firewall itself or ask your provider to test from their side to isolate where the slowdown is.

Plan the Network Before the Circuit Arrives

The easiest way to avoid a disappointing speed test is to review the internal network before the 10 Gig circuit is installed. A quick assessment shows which firewall, switches, and cabling need to change, so you don't pay for bandwidth your network can't use.

Tierzero delivers 10 Gig Fiber along with the managed firewall, switching, Wi-Fi, and cabling to match. Read more about what it takes to get full value from 10 Gig, or talk to us about a network review. If you already have 10 Gig and aren't seeing the speed, we can help find the bottleneck.