Cisco Certified Network Professional 2025 – 400 Free Practice Questions to Pass the Exam

The redundancy mode that necessitates both supervisors to run the same IOS version is Stateful Switchover (SSO). This is important because SSO provides high availability by allowing one supervisor engine to take over seamlessly for another in the event of a failure. For this to happen effectively, both supervisors must maintain identical operating environments, including the same IOS software version, configurations, and state information.

In environments where SSO is implemented, both supervisors actively maintain the system's operational integrity and can synchronize their states. If one supervisor fails, the other can quickly assume control without loss of traffic, which is critical for maintaining uptime in enterprise networks.

Other redundancy modes like RPR (Route Processor Redundancy) and RPR+ do not require the same stringent conditions regarding the IOS versions, as they handle failover differently. StackWise pertains to a different type of architecture that allows multiple switches to operate as a single switch but does not depend solely on the IOS version for redundancy purposes. These differences highlight why SSO specifically mandates identical IOS versions for both supervisor modules for optimal functional redundancy.