AT-S63 Management Software Features Guide
Section II: Advanced Operations
137
Overview
An access control list is a filter that controls the ingress traffic on a port. It
defines a category of traffic and the action of the port when it receives
packets of the category. The action can be to accept the defined packets
or discard them. You can use this feature to increase the security to your
network by restricting access to certain areas or subnets, or to enhance
network performance by forming network links dedicated to carrying
specified types of traffic.
Note
This feature is not related to the management ACL feature,
described in Chapter 39, “Management Access Control List” on
page 455. They perform different functions and are configured in
different ways.
The heart of an ACL is a classifier. A classifier, as explained “Overview” on
page 127, defines packets that share a common trait. Packets that share a
trait are referred to as a traffic flow. A traffic flow can be very broad, such
as all IP packets, or very specific, such as packets from a specified end
node destined for another specified node. You specify the traffic using
different criteria, such as source and destination MAC addresses or
protocol.
When you create an ACL, you must specify the classifier that defines the
traffic flow to permit or deny on a port.
There are two kinds of ACLs based on the two actions that an ACL can
perform. One is called a permit ACL. Packets that meet the criteria in a
permit ACL are accepted by a port.
The second type of ACL is a deny ACL. This type of ACL denies entry to
packets that meet the criteria of its classifiers, unless the packet also
meets the criteria of a permit ACL on the same port, in which case the
packet is accepted. This is because a permit ACL overrides a deny ACL.
Here is an overview of how the process works.
1. When an ingress packet arrives on a port, it is checked against the
criteria in the classifiers of all the ACLs, both permit and deny,
assigned to the port.
2. If the packet matches the criteria of a permit ACL, the port immediately
accepts it, even if the packet also matches a deny ACL assigned to the
same port, because a permit ACL always overrides a deny ACL.
3. If a packet meets the criteria of a deny ACL but not any permit ACLs
on the port, then the packet is discarded.
Summary of Contents for AT-S63
Page 14: ...Figures 14 ...
Page 18: ...Tables 18 ...
Page 28: ...28 Section I Basic Operations ...
Page 58: ...Chapter 1 Overview 58 ...
Page 76: ...Chapter 2 AT 9400Ts Stacks 76 Section I Basic Operations ...
Page 96: ...Chapter 5 MAC Address Table 96 Section I Basic Operations ...
Page 114: ...Chapter 8 Port Mirror 114 Section I Basic Operations ...
Page 116: ...116 Section II Advanced Operations ...
Page 146: ...Chapter 12 Access Control Lists 146 Section II Advanced Operations ...
Page 176: ...Chapter 14 Quality of Service 176 Section II Advanced Operations ...
Page 196: ...196 Section III Snooping Protocols ...
Page 204: ...Chapter 18 Multicast Listener Discovery Snooping 204 Section III Snooping Protocols ...
Page 216: ...Chapter 20 Ethernet Protection Switching Ring Snooping 216 Section III Snooping Protocols ...
Page 218: ...218 Section IV SNMPv3 ...
Page 234: ...234 Section V Spanning Tree Protocols ...
Page 268: ...268 Section VI Virtual LANs ...
Page 306: ...Chapter 27 Protected Ports VLANs 306 Section VI Virtual LANs ...
Page 320: ...320 Section VII Internet Protocol Routing ...
Page 360: ...Chapter 30 BOOTP Relay Agent 360 Section VII Routing ...
Page 370: ...Chapter 31 Virtual Router Redundancy Protocol 370 Section VII Routing ...
Page 372: ...372 Section VIII Port Security ...
Page 402: ...Chapter 33 802 1x Port based Network Access Control 402 Section VIII Port Security ...
Page 404: ...404 Section IX Management Security ...
Page 436: ...Chapter 36 PKI Certificates and SSL 436 Section IX Management Security ...
Page 454: ...Chapter 38 TACACS and RADIUS Protocols 454 Section IX Management Security ...
Page 462: ...Chapter 39 Management Access Control List 462 Section IX Management Security ...
Page 532: ...Appendix D MIB Objects 532 ...