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Cisco Catalyst 6500 Series Switches

Catalyst 6500 Switches Ternary Content Addressable Memory Customization

Document ID: 116132

Updated: Dec 19, 2014

Contributed by Shashank Singh, Cisco TAC Engineer.

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Introduction

This document describes how to customize the forwarding information base (FIB) ternary content addressable memory (TCAM) on Catalyst 6500 switches that run the Supervisor Engine 720.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

The information in this document is based on a Cisco Catalyst 6500 switch that runs on a Supervisor Engine 720 with PFC3BXL/PFC3CXL.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Problem

As outlined in the datasheet, PFC3BXL and PFC3CXL support one millon (1M) IPv4 routes and 512,000 (512k) IPv6 routes. However, default outputs look different:

6500#show mls cef maximum-routes 
FIB TCAM maximum routes :
=======================
Current :
---------
 IPv4 + MPLS         - 512k (default)
 IPv6 + IP Multicast - 256k (default)

Solution

The default numbers for PFC3BXL/PFC3CXL are 512k IPv4 routes and 256k IPv6 routes. These numbers can be increased to 1M IPv4 OR 512k IPv6 routes if you enter mls cef maximum-routes ip|ipv6 [] and reload. But, you cannot achieve both 1M IPv4 AND 512k IPv6 routes at the same time. If you increase the IPv4 TCAM size above the default value, it automatically takes up the IPv6 space and vice versa.

On August 8, 2014, the Classless Inter-Domain Routing (CIDR) Report, which provides statistics on the Global Internet Routing Table, reported that the Global Internet Routing Table has passed 512,000 routes. This example shows how you can increase the default TCAM space of 512,000 IPv4 routes to 768,000 IPv4 routes:

6500(config)#mls cef maximum-routes ip ?
  <1-1007>  number of 1K entries

6500(config)#mls cef maximum-routes ip 768
Maximum routes set to 786432. Configuration will be effective on reboot.


(After reload)
6500#show mls cef maximum-routes
FIB TCAM maximum routes:
=======================
IPv4                - 768k  
 MPLS                - 16k (default)
 IPv6 + IP Multicast - 120k (default)
Updated: Dec 19, 2014
Document ID: 116132