34-2
Cisco IE 3000 Switch Software Configuration Guide
OL-13018-03
Chapter 34 Configuring Network Security with ACLs
Understanding ACLs
An ACL contains an ordered list of access control entries (ACEs). Each ACE specifies
permit
or
deny
and a set of conditions the packet must satisfy in order to match the ACE. The meaning of
permit
or
deny
depends on the context in which the ACL is used.
The switch supports IP ACLs and Ethernet (MAC) ACLs:
•
IP ACLs filter IPv4 traffic, including TCP, User Datagram Protocol (UDP), Internet Group
Management Protocol (IGMP), and Internet Control Message Protocol (ICMP).
•
Ethernet ACLs filter non-IP traffic.
This switch also supports quality of service (QoS) classification ACLs. For more information, see the
“Classification Based on QoS ACLs” section on page 36-7
.
These sections contain this conceptual information:
•
Port ACLs, page 34-2
•
Handling Fragmented and Unfragmented Traffic, page 34-3
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 and can be applied only on interfaces in the
inbound direction. These 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 associated with all inbound features configured on a given 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.
Figure 34-1
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 prevent Host B from
accessing the same network. Port ACLs can only be applied to Layer 2 interfaces in the inbound
direction.