Different Versions of the SSH Protocol
The current version of the SSH protocol is version 2
(SSH2). More information on the protocol can be
found in the IETF-secsh Internet-Drafts
(http://www.ietf.org/ID.html).
Note: SSH Communications Security considers the Secure
Shell protocol version 1 (SSH1) deprecated and does not
recommend the use of it. The SSH statement regarding the
vulnerability of SSH1 protocol is available at http://www.ssh.com/company/newsroom/article/210/.
Several different versions of the Secure Shell client and
server exist. Please note that the different versions may use
different implementations of the ssh protocol, and therefore
you may not be able to connect to an ssh1 server using ssh2
client software, or vice versa.
However, the SSH Secure Shell server software includes support
for fallback functionality if SSH Secure Shell version 1.x is
already installed. (SSH Secure Shell for Windows Servers does
not include this functionality.) Furthermore, the SSH Secure
Shell client now contains internal ssh1 emulation, allowing it
to communicate with ssh1 servers without using an external ssh1
program.
For optimal results, however, upgrade all servers and clients
to the latest available version of SSH Secure Shell.
Please note that the version number of the SSH Secure Shell
software product does not reflect the version number of the
secure shell protocol, but the version of the software.
