Your ssh is configured with the defaults options using /etc/ssh/sshd_config.
Code:
# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented. Uncommented options change a
# default value.
#Port 22
#Protocol 2,1
#ListenAddress 0.0.0.0
#ListenAddress ::
You can uncomment the "Protocol 2,1" line , and make a restart of sshd service, to work on both protocols.
Anyway, ssh2 is safer and better than ssh1.