Cisco Cisco Catalyst 4506-E Switch Troubleshooting Guide
ACL and QoS TCAM
Exhaustion Avoidance on
Catalyst 4500 Switches
Exhaustion Avoidance on
Catalyst 4500 Switches
Document ID: 66978
Contents
Introduction
Prerequisites
Requirements
Components Used
Conventions
Background Information
Catalyst 4500 ACL and QoS Hardware Programming
Architecture
Architecture
Types of TCAM
Troubleshoot TCAM Exhaustion
Suboptimal TCAM Programming Algorithm for TCAM 2
Excessive Use of L4Ops in an ACL
Excessive ACLs for the Supervisor Engine or Switch Type
Summary
NetPro Discussion Forums - Featured Conversations
Related Information
Introduction
Cisco Catalyst 4500 and Catalyst 4948 series switches support the wire-rate access control list (ACL)
and QoS feature with use of the ternary content addressable memory (TCAM). The enablement of ACLs
and policies does not decrease the switching or routing performance of the switch as long as the ACLs
are fully loaded in the TCAM. If the TCAM is exhausted, the packets may be forwarded via the CPU
path, which can decrease performance for those packets. This document provides details about:
and QoS feature with use of the ternary content addressable memory (TCAM). The enablement of ACLs
and policies does not decrease the switching or routing performance of the switch as long as the ACLs
are fully loaded in the TCAM. If the TCAM is exhausted, the packets may be forwarded via the CPU
path, which can decrease performance for those packets. This document provides details about:
The different types of TCAM that the Catalyst 4500 and Catalyst 4948 use
How the Catalyst 4500 programs the TCAMs
How to optimally configure the ACLs and TCAM on the switch in order to avoid TCAM
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Cisco - ACL and QoS TCAM Exhaustion Avoidance on Catalyst 4500 Switches
10/18/2005
http://www.cisco.com/warp/customer/473/tcam_cat_4500.html