September 28, 2009

Deploying Redundant Supervisors for Maximum Uptime

  • Cisco Catalyst 6500 High Availability
  • Cisco Systems

The Cisco® Catalyst® 6500 is deployed in the most critical parts of enterprise and service provider networks. Having such a vital position in the network, the Cisco Catalyst 6500 must provide the highest levels of availability. To achieve these levels of availability network engineers employ both network wide technologies as well as device level redundancy. This includes network designs with redundant switches, redundant paths using Cisco EtherChannel® technology, First Hop Redundancy Protocols, the Cisco Virtual Switching System (VSS) and of course redundant system components including power supplies, fans and Supervisor modules.

This paper discusses the Redundant Supervisor technologies for the Cisco Catalyst 6500. These technologies have evolved over time from nonstateful, Route Processor Redundancy mode (RPR) to the current Stateful Switchover (SSO) mode with Nonstop Forwarding (NSF). The newest addition to the suite of Redundant Supervisor technologies is the In-Service Software Upgrade (ISSU) technology which enables redundant Supervisors to use the SSO redundancy mode even when running different versions of Cisco IOS® Software. The new ISSU versioning infrastructure allows for a streamlined software upgrade process with minimal downtime when performing full image software upgrades. The ISSU process can also be used to activate Maintenance Packs within Cisco IOS Software Modularity. The new ISSU infrastructure provides a significant improvement for full image software upgrades when performed with the Cisco Virtual Switching System (VSS).

This paper describes the NSF and SSO platform-specific details. Although it is not the primary goal of this paper, it is very important for readers to understand how to design a highly available network with NSF and SSO. For high-availability campus network design information, in-depth information about generic NSF with SSO operations and Multicast Multilayer Switching (MMLS) NSF with SSO is included.

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