Troubleshooting Slow Network Throughput with iPerf3
We broke a healthy lab path three ways on real Cisco routers. Learn the three fingerprints of slow throughput and the iPerf3 tests that expose each.
iPerf
Measuring throughput instead of guessing at it. Articles tagged iPerf cover TCP and UDP tests, tuning windows and parallel streams, and reading results from a real Linux host.
Latest posts
Running an iPerf3 Server: Daemon Mode, Ports, and Logging
Foreground vs daemon mode, the one-test-at-a-time busy error, multi-port servers, systemd units, and the firewall rules an iPerf3 test server actually needs.
iPerf2 vs iPerf3: Differences That Actually Matter
Two tools, not two versions: they do not interoperate, flags collide, and each wins different jobs. Real output from iperf 2.2.1 and 3.18 shows exactly where they differ.
iPerf3 Parallel Streams and TCP Window Size (-P and -w)
Why fast links benchmark slow: bandwidth-delay product, a real 78% throughput collapse from a 64K window at 104 ms RTT, and how parallel streams buy it back.
iPerf3 UDP Testing: Bandwidth, Jitter, and Packet Loss
UDP mode measures what TCP hides: loss, jitter, and reordering. Real lab captures show a clean test, a 29% loss over-drive, and how to find the loss knee on any path.
Featured
How to Use iPerf3: Commands and Examples From a Real Lab
Learn iPerf3 from install to JSON automation, with every output block captured live from a routed Cisco lab - including how to actually read Retr, Cwnd, and sender vs receiver lines.