Implementing Cisco Network Security (IINS v3.0) (#63)

What is a valid implicit permit rule for traffic that is traversing the ASA firewall?

ARPs in both directions are permitted in transparent mode only.
Unicast IPv4 traffic from a higher security interface to a lower security interface is permitted in routed mode only.
Unicast IPv6 traffic from a higher security interface to a lower security interface is permitted in transparent mode only.
Only BPDUs from a higher security interface to a lower security interface are permitted in transparent mode.
Only BPDUs from a higher security interface to a lower security interface are permitted in routed mode.