Windows SSH Client - Incorrect MAC Algorithm

When connecting to IP Fabric using the built-in Windows SSH client (OpenSSH for Windows), the connection may fail with the following error:

Corrupted MAC on input.
ssh_dispatch_run_fatal: Connection to x.x.x.x port 22: message authentication code incorrect

This is a known bug in the Windows SSH client (OpenSSH for Windows), which may negotiate the umac-128-etm@openssh.com or umac-128@openssh.com MAC (Message Authentication Code) algorithms incorrectly. The issue is not caused by IP Fabric but by the Windows SSH client’s handling of these MAC algorithms.

Fix

To resolve this issue, explicitly specify a compatible MAC algorithm using the -m option when connecting:

ssh -m hmac-sha2-512-etm@openssh.com osadmin@<IP_FABRIC_ADDRESS>

This forces the SSH client to use the hmac-sha2-512-etm@openssh.com algorithm, which is fully supported and avoids the error.

Persistent Configuration

To avoid specifying the -m option every time, you can add the following to your SSH configuration file (%USERPROFILE%\.ssh\config):

Host <IP_FABRIC_ADDRESS>
    MACs hmac-sha2-512-etm@openssh.com