Firewalls configured as High
Availability (HA) peers must be able to communicate with
each other to maintain state information (HA1 control link) and synchronize
data (HA2 data link). In Active/Active HA deployments the peer firewalls
must also forward packets to the HA peer that owns the session.
The HA3 link is a Layer 2 (MAC-in-MAC) link and it does not support
Layer 3 addressing or encryption.
Used for the HA1 control link for clear
text communication between the HA peer firewalls. The HA1 link is
a Layer 3 link and requires an IP address.
Used for the HA1 control link for encrypted
communication (SSH over TCP) between the HA peer firewalls.
Listening port for HA1 backup links.
Used for heartbeat backups. Palo Alto Networks
recommends enabling heartbeat backup on the MGT interface if you
use an in-band port for the HA1 or the HA1 backup links.
Used for the HA2 link to synchronize sessions,
forwarding tables, IPSec security associations and ARP tables between firewalls
in an HA pair. Data flow on the HA2 link is always unidirectional
(except for the HA2 keep-alive); it flows from the active firewall
(Active/Passive) or active-primary (Active/Active) to the passive
firewall (Active/Passive) or active-secondary (Active/Active). The
HA2 link is a Layer 2 link, and it uses ether type 0x7261 by default.
HA data link can also be configured to use either IP (protocol number
99) or UDP (port 29281) as the transport, and thereby allow the
HA data link to span subnets.