SSH Shell - An unexpected error occurred. Error code: FAIL_PROTOCOL_ERROR

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SSH Shell - An unexpected error occurred. Error code: FAIL_PROTOCOL_ERROR

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pankracyolejniczak

Hi,

I'm trying to set up regular SSH connection to Cisco switch (in terminal/powershell - ssh admin@switch).
In MobaXTerm I have no issues, but in RDM, I'm getting this error.

Is there any setting that I should change? I have everything on Default, it is a SSH Shell selected as connection type and port is 22. No SSH key login, just regular login/password. No matter if it set or not, the terminal does not open.

77f5237c-9f8c-4ff6-9e28-ced05f6744c7.png

avatar
pankracyolejniczak

Recommended Answer

That was it! Thank you very much.
I couldn't find any logs in the app, I had to enable in the session settings - thanks for showing this tip.
For the refference, DH group and MAC were missing.

[24.06.2026 18:22:20] Devolutions.ProtocolsSharp: 2026.1.26.1 OS: Windows

[24.06.2026 18:22:20] Terminal font: Courier New [Courier New, fixed=True]

[24.06.2026 18:22:20] Starting SSH, verbose level: 2

[24.06.2026 18:22:20] Setting up connection

[24.06.2026 18:22:20] Connecting to: x.y.z.u (IPV_ANY)

[24.06.2026 18:22:20] SSH version banner: SSH-2.0-Cisco-1.25

[24.06.2026 18:22:20] Sending kex init

[24.06.2026 18:22:20] Received kex init

[24.06.2026 18:22:20] SSH algo negociation failed:
  enable kex: diffie-hellman-group14-sha1
  enable mac: hmac-sha1

All Comments (2)

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Min Destens

Hello,

Could you please enable the verbose logs.

Perhaps it is related to the SSH Algorithm configuration.

Regards,
Min

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Min Destens

Hello,

Nice, I'm glad to hear, thanks for sharing the solution! 😎

Regards,
Min