Static NAT is bidirectional on SRX Series Firewalls. It creates a fixed one-to-one translation between an original address and a translated address, allowing sessions to be initiated from either side of the gateway. Destination NAT, by contrast, allows inbound access to internal resources but is not inherently bidirectional in the same way. Source NAT translates the source address for outbound connections, commonly allowing private hosts to access public networks, and return traffic is handled by the session table. Source NAT without PAT still does not provide the automatic reverse mapping behavior of static NAT. Juniper documentation notes that static NAT mappings allow connections to be established from either side, which makes static NAT the correct answer.