Abastion hostis a hardened system placed at the boundary between different security zones. It acts as a gateway, controlling access from a less secure network (such as the internet or a lower-trust zone) into a higher-security zone (such as an internal cloud environment).

Secure Shell (SSH) provides secure communication but does not create a boundary. Virtual clients and host isolation are endpoint measures, not boundary defenses.

By placing a bastion host at the perimeter, organizations centralize monitoring, apply strict access controls, and reduce attack surfaces. These hosts are typically stripped down to essential services, patched frequently, and monitored closely. In cloud environments, bastion hosts are essential for controlling administrative access while enforcing strong authentication and logging.