# bandwidth-test > Runs a bandwidth test against the bandwidth test server of another RouterOS device (/tool/bandwidth-server) and prints the results every second until duration ends or you stop it. The test sends TCP or UDP traffic in... ----------- ## tool/bandwidth-test **Type:** Command Runs a bandwidth test against the bandwidth test server of another RouterOS device ([`/tool/bandwidth-server`](bandwidth-server/)) and prints the results every second until `duration` ends or you stop it. The test sends TCP or UDP traffic in one or both directions; the server must be enabled, reachable on TCP port 2000 and UDP ports from its `allocate-udp-ports-from`, and the `bandwidth-test` device mode must be on (see [Device mode](../../system-information-and-utilities/device-mode)). The server lists running tests in [`/tool/bandwidth-server/session`](bandwidth-server/session). To measure latency and both directions of TCP and UDP in one run, use [`/tool/speed-test`](speed-test). See [Bandwidth test](../../diagnostics-monitoring-and-troubleshooting/bandwidth-test). IPv4 or IPv6 address of the server. A link-local IPv6 address needs the interface, for example `fe80::1%ether1`. Traffic to send: - `udp` (default) - UDP packets of `local-udp-tx-size` and `remote-udp-tx-size` bytes; the receiver counts lost packets. - `tcp` - TCP connections (`connection-count`); TCP adapts its rate to the path. Size of the UDP packets the client sends, in bytes of the whole IP packet: 1500 sends a 1472-byte UDP payload. Values below 52 fail with `failure: size too small` over IPv4. Range `28..64000`. Default: 1500. Size of the UDP packets the server sends, counted the same way as `local-udp-tx-size`. Default: 1500. Which side sends: - `receive` (default) - The server sends, the client receives (`rx-*` values). - `transmit` - The client sends, the server receives (`tx-*` values). - `both` - Both sides send at the same time. Number of TCP connections, or of UDP streams with their own ports, that the test uses. Range `1..255`. Default: 20, or the number of CPU cores on routers with more than 20 cores. Maximum rate the client sends at, in bits per second (suffixes such as `50M` work). Without it, the client sends as fast as it can: an unlimited UDP test floods for about the first second and then sends more than the receiver reports, so `lost-packets` stays above zero. Maximum rate the server sends at, in bits per second (suffixes such as `50M` work). Without it, the server sends as fast as it can. User name on the server. The user's group needs both the `test` and `winbox` policies (see [`/user/group`](../user/group)). Not needed when the server has `authenticate=no`. Password of `user` on the server. How long the test runs. Without it, the test runs until you stop it, for example with Control+C. Whether to fill the payload with random, incompressible data, so that links that compress traffic do not show a higher rate than they carry. It costs more CPU time on both sides. Default: no. State of the test: - `connecting` - The client is connecting to the server. - `running` - The test runs. - `done testing` - The test ended after `duration`. - `authentication failed` - The server refused the user name or password, or no user was given while the server authenticates. - `can not connect` - The server is disabled or not reachable, the client is not in its `allowed-addresses4`/`allowed-addresses6`, or `max-sessions` is reached. - `disconnected` - The connection to the server ended during the test, also when the test uses more connections than the server's `max-sessions`. Other values report that the server refused or could not start the test. How long the test has run. Rate the client sent at in the last second. UDP counts whole IP packets (IP and UDP headers included), TCP counts the TCP payload only. Average rate the client sent at over the last 10 seconds. Average rate the client sent at since the test started. Rate the client received at in the last second. UDP counts whole IP packets (IP and UDP headers included), TCP counts the TCP payload only. Average rate the client received at over the last 10 seconds. Average rate the client received at since the test started. UDP packets lost in the last second, not a total since the start. Whether the test uses random data (`random-data`). Direction of the test (`direction`). Size of the UDP packets the client sends, in bytes of the whole IP packet. Size of the UDP packets the client receives, in bytes of the whole IP packet. Number of TCP connections or UDP streams the test uses. CPU load of the client during the test, shown after the first seconds. CPU load of the server during the test, shown after the first seconds.