Problem: PaloAlto firewall is dropping packets in small bursts of some seconds, and sometimes it drops TCP connections. It only happens on HA clusters on interfaces in active/passive (fail over) mode.
Solution: disable the following check box in the Ethernet interface Advanced – LLDP settings: “Enable in HA Passive State”
Discussion: Palo Alto uses only one MAC address for both machines of an HA cluster. The passive box sends LLDP packets using this MAC address. The switch learns this MAC address and sends the traffic to the passive node until the active node sends new packets. The passive node should never send packets with the MAC address of the active node, and should have its own MAC address for LLDP and possibly other services.
Version: PaloAlto current version of Nov 2016, connected to a Cisco Catalyst 6500