ssh server compatible-ssh1x enable

The earlier version-compatible function of an SSH server is applicable to the protocol version negotiation between the client and server. The client negotiates the protocol version, by comparing its own protocol version with the received packet. After a TCP connection is set up between the client and server, the SSH client starts to negotiate with the server on the protocol version by running which they can work normally.

By comparing the protocol versions, the server determines whether to work with the client.

• If the client runs a protocol version that is earlier than 1.3 or later than 2.0, version negotiation fails and the server terminates the TCP connection with the client.
• If the client runs a protocol version that is between 1.3 and 1.99 (including V1.3), the SSH1.5 server module is established when the "compatibility configuration option" of SSH is SSH1.x-compatible. The system then proceeds with the SSH1.x process. The server terminates the TCP connection with the client when the "compatibility configuration option" of SSH is SSH1.x-incompatible.
• That is 1.99 or 2.0, the SSH2.0 server module is established. The system then proceeds with the SSH2.0 process.

• All the connections from the SSH 1.x client are dropped, if the compatibility with SSH 1.3 and 1.5 is disabled.
• If the SSH server is enabled to be compatible with earlier SSH versions, the system prompts a security risk.
• SSHv1 is not secure, and SSHv2 is recommended.
• The configuration takes effect upon the next login.