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Editorial Team
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Asked: 2026-05-29T15:27:20+00:00

When I attempt to access mysql over an SSH tunnel, I get the error:

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When I attempt to access mysql over an SSH tunnel, I get the error:

ERROR 2005 (HY000): Unknown MySQL server host '[serverhost]' (0)

When I make the attempt through MySQL Workbench or over an ordinary SSH CLI, it works fine, though. What am I doing wrong? (I have scanned multiple related threads on this site, but none that explained this behaviour to me.)

TMI:

The host I have is a name, not an IP.

I open the tunnel thus:

plink.exe [user]@[remote-ip] -P [ssh-port] -pw [pw] -L [local-listen-port]:localhost:[remote-mysql-port]

I call mysql on my command line (through tunnel) thus:

mysql -h [serverhost] -u [user] -p[pw] --port [local-listen-port]

I call mysql over an SSH command line (no tunnel) thus:

mysql -h [serverhost] -u [user] -p[pw] --port [remote-mysql-port]
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1 Answer

  1. Editorial Team

    Your existing plink command is wrong, as its specifying localhost as the destination address (which is the localhost on the other side of the SSH session, so [remote-ip], by your reckoning, which is why you are getting an error) – it should be [serverhost].

    Then, you are then mistakenly attempting to connect mysql directly to [serverhost], but the tunnel does not affect routing, so that is incorrect, you should be connecting to localhost.

    Your existing example command works when connected to an ssh shell session on [remote-ip], because you are connecting from [remote-ip], which has access to [serverhost] presumably.

    Assuming [serverhost] is the remote server, your commands should be:

    plink.exe [user]@[remote-ip] -P [ssh-port] -pw [pw] -L [local-listen-port]:[serverhost]:[remote-mysql-port]

    Then

    mysql -h localhost -u [user] -p[pw] --port [local-listen-port]

    EDIT: Let me try and diagram it for you, since you are obviously misunderstanding the nature of the tunnel:

    The SSH connection

    localhost[?] <——–> remote-ip[22]

    The tunnel

    localhost[local-port] <—- SSH —> remote-ip[22] <— TCP —>
    serverhost[remote-port]

    Therefore, SSH/plink has bound a port on localhost, using the [local-port] number you have specified, that, when receiving a connection request, establishes a connection from [remote-ip] to [serverhost:remote-port], then shuffles the sends/receives back and forth between them, using its own SSH connection for the hop from [localhost] to [remote-ip].

    So – once the tunnel has been set up, to access [serverhost:remote-port], you actually point your tools at [localhost:local-port], and the tunnel routes the traffic to the appropriate place.

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