From the Ubuntu client, execute $$ssh $192\mathrm{.}168\mathrm{.}0\mathrm{.}200.$ Why you did not succeed? Then, try with $$ssh herzing@$192\mathrm{.}168\mathrm{.}0\mathrm{.}200$ and, once connected, execute $$whoami$.$ Finally, quit the session with $$exit$.$