Document ID: 109547

PDF Downloads Cisco Catalyst 6500 Virtual Switching System Deployment Best Practices

Introduction

This document provides best practices for Cisco Catalyst 6500 Virtual Switching System 1440 deployment scenarios.

This document provides modular configuration guidance. Therefore, you can read each section independently and make changes in a phased approach. This document assumes a basic comprehension and familiarity with the Cisco IOS® Software user interface. The document does not cover overall network design.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

This document is not restricted to specific software and hardware versions.

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.

Conventions

Refer to Cisco Technical Tips Conventions for more information on document conventions.

VSS Deployment Best Practices

The solutions that this document offers represent years of field experience from Cisco engineers who work with complex networks and many of the largest customers. Consequently, this document emphasizes configurations that make networks successful. This document offers these solutions:

• Solutions that are easy to manage and that network operations teams configure

• Solutions that promote high availability and high stability

VSS High Availability

• Non Stop Forwarding

• OOB MAC Synchronization

Non Stop Forwarding

Catalyst 6500 series switches support fault resistance, because it allows a redundant supervisor engine to take over if the primary supervisor engine fails. Cisco Non Stop Forwarding (NSF) works with Stateful SwitchOver (SSO) in order to minimize the amount of time a network is unavailable to its users after a switchover while IP packets continue to be forwarded.

Recommendations

• Non Stop Forwarding is required for supervisor switchover convergence at sub-second time.

• Use default Hello and Dead timers for EIGRP / OSPF protocols when you run in a VSS environment.

• If you run the system with modular Cisco IOS software, it is recommended to go for larger value OSPF Dead timer.

EIGRP

Switch(config)# router eigrp 100
Switch(config-router)# nsf

Switch# show ip protocols
*** IP Routing is NSF aware ***

Routing Protocol is "eigrp 100"

!--- part of the output truncated

EIGRP NSF-aware route hold timer is 240s

!--- indicates that EIGRP is configured to be NSF aware


!--- part of the output truncated

EIGRP NSF enabled

!--- indicates that EIGRP is configured to be NSF capable


!--- rest of the output truncated

OSPF

Switch(config)# router ospf 100
Switch(config-router)# nsf

Switch# show ip ospf
Routing Process "ospf 100" with ID 10.120.250.4
Start time: 00:01:37:484, Time elapsed: 3w2d

!--- part of the output truncated

Supports Link-local Signalling (LLS)

!--- indicates that OSPF is configured to be NSF aware


!--- part of the output truncated

Non-Stop Forwarding enabled, last NSF restart 3w2d ago (took 31 secs)

!--- indicates that OSPF is configured to be NSF capable


!--- rest of the output truncated

Refer to Configuring NSF with SSO Supervisor Engine Redundancy for more information on NSF.

OOB MAC Synchronization

In distributed switching, each Distributed Feature Card (DFC) maintains its own CAM table. This means that each DFC learns the MAC address and ages them, which depends on the CAM aging and traffic matching of that particular entry. With distributed switching, it is normal that the supervisor engine does not see any traffic for a particular MAC address for a while, so the entry can expire. There are currently two mechanisms available to keep the CAM tables consistent between the different engines, such as DFC, which is present in line modules, and Policy Feature Card (PFC), which is present in supervisor modules:

• Flood to Fabric (FF)

• MAC Notification (MN)

When a MAC address entry is aged out on the PFC, the show mac-address address <MAC_Address> all command displays the DFC or PFC that holds this MAC address. In order to prevent the age out of an entry on a DFC or PFC, even if there is not traffic for that MAC address, enable the MAC address synchronization. Issue the mac-address-table synchronize global configuration command and clear mac-address-table dynamic privileged EXEC command in order to enable the synchronization. This mac-address-table synchronize command is available from Cisco IOS Software Releases 12.2(18)SXE4 and later. After you enable it, it is possible to still see entries that are not present in PFC or DFC. However, the module has a way to learn it from others that use Ethernet Out of Band Channel (EOBC).

Recommendations

Enable Out-of-Band MAC synchronization. It is used in order to synchronize mac-address tables across the forwarding engines. If WS-6708-10G is present in the VSS system, MAC synchronization is automatically enabled. If not, it must be enabled manually.

Dist-VSS(config)# mac-address-table synchronize
% Current activity time is [160] seconds
% Recommended aging time for all vlans is atleast three times the activity interval

Dist-VSS# clear mac-address-table dynamic
% MAC entries cleared.

Dist-VSS# show mac-address-table synchronize statistics

MAC Entry Out-of-band Synchronization Feature Statistics:
---------------------------------------------------------
Switch [1] Module [4]
---------------------
Module Status:
Statistics collected from Switch/Module   : 1/4
Number of L2 asics in this module         : 1

Global Status:
Status of feature enabled on the switch   : on
Default activity time                     : 160
Configured current activity time          : 480

Capacity Planning for Virtual Switch Link (VSL)

Ideally in dual-homed VSS configuration, no data traffic is sent on the VSL link. Each switch is programmed to choose its local interfaces for traffic forwarding.

Additional VSL link capacity planning is required for traffic carried by:

• Single homed devices

• Remote SPAN from one switch to another

• Service module traffic â