Unable to negotiate with <mc_ip> port yyyyy: no matching host key type found.

Products

• Management Center - VA

Issue/Introduction

The customer has deployed new backup server and I am trying to adjust the job for exporting backups so it will transfer the backups to the new server. 

I was able to easily adjust the MC backups, but for the backup export job for backing up ProxySG and CAS I meet several problems. 

Unable to retrieve the "Host Public Key", with SCP. The attempt ends with "Unexpected Error - Incorrect protocol" message.
Unable to run the backup even without the "Host Public Key" in place. The attempts fails with the message " Error: An unexpected server error occurred"

The logs on the backup server show problem with algorithms: 
sshd[182965]: Unable to negotiate with <mc_ip> port yyyyy: no matching host key type found. The server offers: ssh-rsa,ssh-dss [preauth]

Environment

Management Center - VA

Cause

If you use SCP to export a backup to a server and you receive an error, check the error message. If the target server does not support at least one of the previous key exchange algorithms, the export might fail with the one of the following messages:

• A connection could not be established
• The secure handshake failed during key exchange

This requirement also applies to other Management Center operations that use SSH/SCP.

Note:

Management Center supports the following key exchange algorithms for SSH/SCP connections:

• DHGex
• DHG
• Curve25519

So the issue is with the incompatibility with the key exchange algorithm.

Resolution

Resolution:

Ensure the backup server offers one of the supported key exchange algorithms, to have the backup export job, with SCP, succeed. MC will negotiate using only the key exchange algorithm it supports.

Ref.: Export Device Backups from Management Center

Additional Information

Linked Case: 35750186