Cisco Catalyst 2960 Series, Configuration Manual

Page: 1250 / 2288

ACL Precedence
When VLAN maps, Port ACLs, and router ACLs are configured on the same switch, the filtering precedence,
from greatest to least, is port ACL, router ACL, then VLAN map. The following examples describe simple
use cases:
• When both an input port ACL and a VLAN map are applied, incoming packets received on ports with
a port ACL applied are filtered by the port ACL. Other packets are filtered by the VLAN map
• When an input router ACL and input port ACL exist in a switch virtual interface (SVI), incoming packets
received on ports to which a port ACL is applied are filtered by the port ACL. Incoming routed IP packets
received on other ports are filtered by the router ACL. Other packets are not filtered.
• When an output router ACL and input port ACL exist in an SVI, incoming packets received on the ports
to which a port ACL is applied are filtered by the port ACL. Outgoing routed IP packets are filtered by
the router ACL. Other packets are not filtered.
• When a VLAN map, input router ACL, and input port ACL exist in an SVI, incoming packets received
on the ports to which a port ACL is applied are only filtered by the port ACL. Incoming routed IP packets
received on other ports are filtered by both the VLAN map and the router ACL. Other packets are filtered
only by the VLAN map.
• When a VLAN map, output router ACL, and input port ACL exist in an SVI, incoming packets received
on the ports to which a port ACL is applied are only filtered by the port ACL. Outgoing routed IP packets
are filtered by both the VLAN map and the router ACL. Other packets are filtered only by the VLAN
map.
Port ACLs
Port ACLs are ACLs that are applied to Layer 2 interfaces on a switch. Port ACLs are supported only on
physical interfaces and not on EtherChannel interfaces. Port ACLs can be applied to the interface only in
inbound direction. The following access lists are supported:
• Standard IP access lists using source addresses
• Extended IP access lists using source and destination addresses and optional protocol type information
• MAC extended access lists using source and destination MAC addresses and optional protocol type
information
The switch examines ACLs on an interface and permits or denies packet forwarding based on how the packet
matches the entries in the ACL. In this way, ACLs control access to a network or to part of a network.
This is an example of using port ACLs to control access to a network when all workstations are in the same
VLAN. ACLs applied at the Layer 2 input would allow Host A to access the Human Resources network, but
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
1168
Information About Access Control Lists