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

Resolved

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

avatar
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.

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 (3)

avatar
Min Destens

Hello,

Could you please enable the verbose logs.

Perhaps it is related to the SSH Algorithm configuration.

Regards,

Min

avatar
pankracyolejniczak

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
avatar
Min Destens

Hello,

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

Regards,

Min