Palo Alto Networks recommends two configuration options for outbound high availability (HA) design in Amazon Web Services using a VM-Series firewall: transit gateway and Security VPC, and traditional active-passive HA. Transit gateway and Security VPC allows you to use a single transit gateway to route traffic between multiple VPCs and the internet, while using a Security VPC to host the VM-Series firewalls. Traditional active-passive HA allows you to use two VM-Series firewalls in an HA pair, where one firewall is active and handles all traffic, while the other firewall is passive and takes over in case of a failure. Reference: [VM-Series Deployment Guide for AWS Outbound VPC]