In a Palo Alto Networks Next-Generation Firewall (NGFW), supporting asymmetric routing with redundancy requires specific features to handle traffic that may not follow the same path in both directions.

Active / active high availability (HA): This feature allows two firewalls to operate in tandem, sharing the traffic load. Active/active HA mode is designed to handle asymmetric routing scenarios where traffic might ingress through one firewall and egress through another, ensuring continuity and redundancy.

non-SYN first packet: This feature is crucial for dealing with non-standard traffic patterns where the initial packet may not always be a SYN packet (typical in TCP connections). It allows the firewall to handle and correctly process such packets, which is essential in asymmetric routing scenarios.