How to test network speed

Quick answer: The three standard tools are speedtest-cli (quick public check), iperf3 (accurate point-to-point measurement) and wget/curl against a test file. Always run several tests, use multiple parallel streams for long-distance links, and remember results are quoted in megabits per second while downloads show megabytes per second (divide by 8).

Overview

A single browser speed test from your laptop says little about your server: it mixes in your home Wi-Fi, ISP and distance. Proper testing runs from the server itself and separates direction (upload vs download), streams (single vs parallel) and endpoints (nearby vs far away).

Before you start

• SSH access to your server.
• An idea of your plan's port speed (see 1G / 10G / 20G ports).
• No other heavy traffic on the server during the test.

Step-by-step guide

1. Quick check with speedtest-cli:

   sudo apt update && sudo apt install -y speedtest-cli   # Debian/Ubuntu
   speedtest-cli --simple

   Results depend on the public test server chosen — repeat with --list / --server ID to pick a closer one.
2. Accurate test with iperf3 (needs a second machine you control):

   sudo apt install -y iperf3
   # on the remote machine:  iperf3 -s
   iperf3 -c REMOTE_IP -P 8        # download 8 parallel streams
   iperf3 -c REMOTE_IP -P 8 -R     # reverse direction

3. Real-file download test:

   wget -O /dev/null TEST_FILE_URL

   Use a test file hosted near your users. wget shows MB/s — multiply by 8 for Mbps.
4. Repeat at different times of day and note the numbers.

Common issues

• Single stream far below port speed on long routes? Normal TCP window behaviour — parallel streams (-P 8) show the real capacity.
• MB/s vs Mbps confusion: 1 Gbps ≈ 118 MB/s in practice; a 40 MB/s wget over intercontinental distance can still be healthy.
• Speedtest server is the bottleneck: public speedtest nodes are often capped — always cross-check with iperf3 or a file download.

When to contact support

If parallel-stream tests to nearby endpoints stay far below your port speed across multiple runs, report it with the exact commands, outputs and timestamps.

Frequently asked questions

Why does speedtest show less than my port speed?

Public speedtest servers are often capped and a single TCP stream cannot fill a fast port over long distances. Cross-check with iperf3 using parallel streams.

What is the difference between MB/s and Mbps?

MB/s is megabytes per second, Mbps is megabits. Multiply MB/s by 8 to get Mbps — 118 MB/s is roughly a full 1 Gbps port.

Which tool gives the most accurate result?

iperf3 with parallel streams (-P 8) between two machines you control, repeated at different times of day.

Related articles

• How to troubleshoot slow network speed
• How to check latency to Cloud2Y locations
• How to download test files
• What is the difference between traffic and bandwidth?

Need a hand? Contact Cloud2Y support →