As a best practice, we don’t encourage using a bastion server as a Smallstep SSH host and a client.
The ideal setup for Smallstep SSH through a bastion is to register the target hosts using the -`--bastion` parameter. Once the target hosts are registered, end users (client side) would run the `SSH [target_host]` command to the target host (not the bastion), and therefore wouldn't need to be aware or concerned with the bastion itself.
For more information on configuring SSH hosts, see our quick start guide here.