Packet filtering process

When an ACL filters a packet, it sequentially compares each ACE's filtering criteria to the corresponding data in the packet until it finds a match. The action indicated by the matching ACE (deny or permit) is then performed on the packet.

Figure 7: Packet-filtering process in an ACL with N entries (ACEs)

The order in which an ACE occurs in an ACL is significant. For example, if an ACL contains six ACEs, but the first ACE allows "Permit Any" forwarding, the ACL permits all IPv6 traffic, and the remaining ACEs in the list do not apply, even if they have a match with any traffic permitted by the first ACE.