Windows Server 2019, SSH server, max number of connections or concurrent users?

Question

We are using Win2019, and enabled the built-in SSH server. We have different client devices (each with different IP addresses) connecting to this SSH server.

We would like to know, on the Win2019 SSH server, is there a limit on max. no. of connections or concurrent users? If yes, what's the default value and how to change it?

I found a sshd_config file under C:\ProgramData\ssh, and found 2 settings seem to be related to what I want, but not quite exactly what I want:

MaxSessions

MaxStartups

From a SSH manual page, https://man.openbsd.org/sshd_config.5

MaxSessions

Specifies the maximum number of open shell, login or subsystem (e.g. sftp) sessions permitted per network connection. Multiple sessions may be established by clients that support connection multiplexing. Setting MaxSessions to 1 will effectively disable session multiplexing, whereas setting it to 0 will prevent all shell, login and subsystem sessions while still permitting forwarding. The default is 10.

MaxStartups

Specifies the maximum number of concurrent unauthenticated connections to the SSH daemon. Additional connections will be dropped until authentication succeeds or the LoginGraceTime expires for a connection. The default is 10:30:100.

Alternatively, random early drop can be enabled by specifying the three colon separated values start:rate:full (e.g. "10:30:60"). sshd(8) will refuse connection attempts with a probability of rate/100 (30%) if there are currently start (10) unauthenticated connections. The probability increases linearly and all connection attempts are refused if the number of unauthenticated connections reaches full (60).

For MaxSessions, honestly, I don't know what is "multiple sessions permitted per network connection" or "multiplexing". Does it mean how many different shell, sftp client software, etc, you can open in the same client device?

For MaxStartups, my understanding is, max no. of connections which is connected, but not-yet login (staying at the password input stage?). This seem not what I want.

Answer 1

Hello lg37456

The product Windows Server / User experience / Session connectivity is primarily focus on windows remote desktop session connectivity.

We would recommend you repost your questions in windows Q&A orstack overflow for SSH related questions. I believe there you will get more professional and effective reply.

Thank you for your understanding and support.

Thanks,

Karlie Weng

Answer 2

Thanks.

I see that your Windows Q&A link is learn.microsoft.com . For anyone who wonders what's the difference between answers.microsoft.com and learn.microsoft.com like me:

https://learn.microsoft.com/en-us/answers/questions/470406/whats-the-difference-between-microsoft-answers-and

Answer 3

Thanks for the additional information, great explanation.