What approach do systems administrators use to isolate a critical system from outside networks?

In the context of isolating a critical system from outside networks, the air gap configuration is the most effective approach. This method involves physically separating a network from any external systems, including the internet and any external networks. The critical system is maintained in a wholly isolated environment, which means it cannot be accessed over any network connections, providing a robust layer of security against potential cyber threats and attacks.

An air gap configuration is particularly important for protecting sensitive information and systems that require the highest levels of security, as it minimizes the risk of exposure to vulnerabilities associated with connectivity. This means that even if a threat exists in the external world, it cannot directly impact the critical system, ensuring data integrity and confidentiality.

Other approaches like jump boxes, screened subnets, and VLAN segmentation offer various levels of security but do not provide the same level of physical isolation as an air gap configuration. While these other methods can enhance security and manage traffic within networks, they still involve some degree of connectivity to external systems, which could introduce risks that an air gap configuration effectively mitigates.