Fix PuTTY's SSH2_MSG_UNIMPLEMENTED error

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Disconnected: Server protocol violation: unexpected SSH2_MSG_UNIMPLEMENTED packet

If you've bumped into this error when connecting to a server with PuTTY then don't worry — it's easy to get fixed.

First — try to update PuTTY to the latest version. It's probably that you're using an older version. If it didn't help then do the following:

  1. Open session configuration.

  2. Go to Connection -> SSH -> Kex

  3. Find “Algorithm selection policy” list.

  4. Find “Diffie-Hellman group exchange” line there.

  5. Move this line down to the last position.

Done! Don't forget to save your session's configuration.

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