BFD is a protocol that recognizes a failure in the bidirectional
path between two forwarding engines, such as interfaces, data links,
or the actual forwarding engines. In the PAN-OS implementation,
one of the forwarding engines is an interface on the firewall and
the other is an adjacent configured BFD peer. The BFD failure detection
between two engines is extremely fast, providing faster failover
than could be achieved by link monitoring or frequent dynamic routing health
checks, such as Hello packets or heartbeats.
After BFD detects a failure, it notifies the routing protocol
to switch to an alternate path to the peer. If BFD is configured
for a static route, the firewall removes the affected routes from
the RIB and FIB tables.
BFD is supported on the following interface types: physical Ethernet,
AE, VLAN, tunnel (Site-to-Site VPN and LSVPN), and subinterfaces
of Layer 3 interfaces. For each static route or dynamic routing
protocol, you can enable or disable BFD, select the default BFD
profile, or configure a BFD profile.