Error: "Remote side unexpectedly closed network connection" via SSH to vCenter Server 9.0.2

Products

• VMware vCenter Server

Issue/Introduction

Unable to log into vCenter Server via an SSH client with the 'root' user and other local accounts.

• Able to SSH to the host with SSO credentials.

• The SSH service is enabled.

• Able to SSH with the 'root' account from other Linux appliances.

• Able to log into the vCenter appliance with the 'root' account though the VM console. 

Environment

vCenter Server 9.0.2

VMware Cloud Foundation (VCF) 9.0.2

 

Cause

Older versions of SSH clients (e.g., PuTTY pre-0.75 and MobaXterm pre-21.2) do not support modern cryptographic negotiation algorithms.
This results in an SSH handshake failure when connecting to the updated OpenSSH daemon in vCenter Server 9.0.2.

Resolution

Upgrade SSH clients to latest version.