Using the management interface as the HA1 backup link helps avoid split brain in active-passive high

availability (HA) pair deployment. High availability (HA) is a feature that provides redundancy and

failover protection for firewalls in case of hardware or software failure. Active-passive HA is a mode

of HA that consists of two firewalls in a pair, where one firewall is active and handles all traffic, while

the other firewall is passive and acts as a backup. Split brain is a condition that occurs when both

firewalls in an HA pair assume the active role and start processing traffic independently, resulting in

traffic duplication, policy inconsistency, or session disruption. Split brain can be caused by network

failures, device failures, or configuration errors that prevent the firewalls from communicating their

HA status and synchronizing their configurations and sessions. Using the management interface as

the HA1 backup link helps avoid split brain in active-passive HA pair deployment. The HA1 interface

is used for exchanging HA state information and configuration synchronization between the firewalls.

Using the management interface as the HA1 backup link provides redundancy and failover protection

for the HA1 interface, ensuring that the firewalls can maintain their HA communication and avoid

split brain. Using a standard traffic interface as the HA2 backup, enabling preemption on both

firewalls in the HA pair, or using a standard traffic interface as the HA3 link do not help avoid split

brain in active-passive HA pair deployment, but they are related features that can enhance

performance and reliability. Reference: Palo Alto Networks Certified Software Firewall Engineer

(PCSFE), [High Availability Overview], [Configure HA Backup Links], [Configure Heartbeat Backup]