Setting up a BFD session between Palo Alto and Cisco ACI Leaf or General Nexus Switch

If Device A (ex. Palo Alto) does not support BFD Echo and only BFD Control Packets, Device B (ex. Cisco Switch) will not utilize BFD Echo and will only use BFD Control Packets for the BFD session. As a result, the highest transmit interval between both peers multiplied by the multiplier = the hold-down time. Without BFD Echo, the hold-down time will be how long the BFD peer will wait till BFD session goes down.

Another consideration is that depending on the Palo Alto model, high CPU control plane traffic will effect BFD and may tear your adjacency/peering down.

I have tested 16 eBGP peers on Palo Alto 3220 connected to ACI leaf-A and 16 other eBGP peers on same Palo Alto connected to ACI leaf-B. If the BFD timers were anything below 900 x 3, after an ACI leaf-A or leaf-B reload the Palo Alto would randomly bring down eBGP neighbors from ACI leaf-B, even though no issue occurred between PAN and ACI leaf-B. BFD would tear down because of a control plane spike as PAN must be processing BFD in software. The only acceptable timers were 900 x 3. Anything lower, the Palo Alto would tear down BFD which would bring down the eBGP Peering.