In order of preference/priority, what factors do you consider in driving an upgrade (or downgrade) with Cisco IOS? If no compelling factors exist, how long would you allow a particular version of IOS to stay running? I’ve seen some switches with uptimes > 5 years. And when upgrading, how is the specific IOS release identified as the upgrade target?
In order of preference/priority, best practice tends to dictate an upgrade based on these factors:
- Vulnerabilities, vulnerabilities, vulnerabilities!
- Attaining new features not currently available— new cards/modules have a “first sup
- Migrating away from retired release trains
- Matching versions on more recently deployed and similar hardware