What is Kex_exchange_identification: connection closed by remote host

'Kex_exchange_identification: connection closed by remote host' is an error message that is often encountered by users when trying to access a remote server using the SSH (Secure Shell) protocol. This error appears when the remote server closes the connection during the key exchange process, which is the first step in establishing a secure SSH connection. 

Why does this happen? 

There are several reasons why the remote server may close the connection during the key exchange process, including: 

• Network connectivity issues: The connection may be disrupted due to network problems such as high latency, packet loss, or a firewall blocking the connection. 
• Misconfigured SSH client: The SSH client may not be configured correctly, causing the key exchange process to fail. 
• Misconfigured SSH server: The remote server may be configured to only allow connections from specific clients, or to only allow connections using specific encryption algorithms. If the client and server do not have a shared encryption algorithm, the connection will be closed. 
• Security issues: If the remote server suspects that the connection is not secure, it may close the connection to protect its resources. 

What to do when facing this error? 

To resolve the 'kex_exchange_identification: connection closed by remote host' error, you need to determine the cause of the issue and take the appropriate steps to fix it. Some common solutions include: 

• Check network connectivity: Ensure that your network connection is stable and not experiencing any issues. 
• Verify SSH client configuration: Check that your SSH client is configured correctly and that the client and server have a shared encryption algorithm. 
• Verify SSH server configuration: If you have access to the remote server, check its configuration to ensure that it is configured to allow connections from your client. 
• Try a different encryption algorithm: If the remote server is only configured to allow connections using specific encryption algorithms, try connecting using a different algorithm. 

In conclusion, the 'kex_exchange_identification: connection closed by remote host' error can be resolved by checking network connectivity, verifying SSH client and server configurations, and trying a different encryption algorithm if necessary. With the right approach, you can quickly establish a secure SSH connection and avoid this error.