Cisco Gigabit Ethernet Switch Module for HP p-Class BladeSystem Software Configuration Guide

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Cisco Gigabit Ethernet Switch Module for HP p-Class BladeSystem Software Configuration Guide
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Chapter 26 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 27-7.
These sections contain this conceptual information:
• Supported ACLs, page 26-2
• Handling Fragmented and Unfragmented Traffic, page 26-4
Supported ACLs
The switch supports two applications of ACLs to filter traffic:
• Port ACLs access-control traffic entering a Layer 2 interface. The switch does not support port
ACLs in the outbound direction. You can apply only one IP access list and one MAC access list to
a Layer 2 interface. For more information, see the “Port ACLs” section on page 26-2.
• VLAN ACLs or VLAN maps access-control all packets (bridged and routed). You can use VLAN
maps to filter traffic between devices in the same VLAN. VLAN maps are configured to provide
access control based on Layer 3 addresses for IPv4. Unsupported protocols are access-controlled
through MAC addresses using Ethernet ACEs. After a VLAN map is applied to a VLAN, all packets
(routed or bridged) entering the VLAN are checked against the VLAN map. Packets can either enter
the VLAN through a switch port or through a routed port after being routed. For more information,
see the “VLAN Maps” section on page 26-3.
You can use input port ACLs and VLAN maps on the same switch. However, a port ACL takes
precedence over a VLAN map. When an input port ACL is applied to an interface that belongs to a
VLAN that has a VLAN map applied, incoming packets received at the interface are filtered by the port
ACL. Other packets are filtered 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 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 26-1 is an example of using port
ACLs to control access to a network when all servers are in the same VLAN. ACLs applied at the Layer