A bastion host should be placed:

A bastion host is a fortified system designed to withstand attacks and is placed beyond the outer perimeter firewall to act as a buffer between the public network and internal systems. Its strategic location ensures it handles external-facing services securely, minimizing risks to internal networks. Placing it inside the DMZ (A) or inline with the data center firewall (B) limits its protective functionality. It is also distinct from honeynet management (D).