Hello friends, welcome back—this is Day 50 of my PCNSA Palo Alto Firewall Training series. In this video I started a very important new topic: High Availability (HA). Honestly, without HA we cannot imagine our world today, because every corporate environment is dependent on network 24x7. I explained the core idea in a simple way: we use two firewalls so that if one device crashes, has power/energy issues, or goes down for any reason, the other firewall can take over and the users still have network available for their productive work. Then I covered the two HA modes Palo Alto supports—Active/Passive and Active/Active. In Active/Passive, one firewall processes traffic while the other stays ready with synced configuration and sessions, so it can handle both existing and new sessions during a failover. In Active/Active, both firewalls process traffic (I will do a dedicated configuration session for these modes later). I also explained HA interface types: HA1 for keepalive/polling and configuration sync, and HA2 for session replication (session table, and related tables like ARP/routing updates). Finally, I explained the failover trigger behavior that’s very important for interviews: the new active firewall takes over the active IP and sends Gratuitous ARP so the switch updates its ARP/MAC table and traffic starts flowing through the currently active firewall.