In critical sectors like hospitals, financial institutions, airports etc., a routine reload, or a maintenance upgrade can have serious consequences. Applications may miss a heartbeat, triggering network reconvergence. This means you’re not just accounting for reload or upgrade times, but also the network recovery time, resulting in overall traffic disruption.
This prompts a key question: how do we at Cisco ensure seamless operations during such events, given that network resiliency is no longer a choice but a necessity?
One such solution is ISSU (In-Service Software Upgrade) that’s available for the Catalyst 9400, 9500, and 9600 switches in Dual SUP HA or StackWise Virtual setups. It achieves its negligible downtime during software upgrades by maintaining data plane traffic flow while seamlessly upgrading the control plane using stateful failover.
Now, what about Catalyst 9300 series switches? Which is built for enterprise access and ensures connectivity for everything - from IoT sensors, servers to Wi-Fi access points and more, even in single-homed setups?
Enter xFSU - New and Enhanced!
Extended Fast Software Upgrade (xFSU) is a software upgrade mechanism designed for Catalyst 9300 series switches, whether deployed in standalone or stacked mode. It minimizes traffic downtime to less than 5 seconds during software upgrades and reloads, with no topology changes, regardless of whether the switch operates as a Layer 2 access node or a Layer 3 routed access node, while also, ensuring hitless Perpetual PoE for uninterrupted power to connected devices.
Peeling back the layers: how does xFSU get the job done?
During a reload or upgrade, it separates the control plane and data plane, leveraging NSF and Graceful Restart for control plane continuity while maintaining data plane traffic. Additionally, it uses cache and flush architecture for the data plane, ensuring minimal traffic disruption during the upgrade process.
Now, xFSU isn't just limited to standalone setups - it also supports stack configurations! For protocols requiring control plane intervention, the stack xFSU reload/upgrade process works seamlessly. It upgrades the standby and member switches first, then performs a stateful switchover to the standby, followed by the active switch reload/upgrade.
This approach keeps the control plane operational, ensuring each switch in the stack experiences less than 5 seconds of traffic downtime only.
And there’s more, xFSU supports flexible deployment across L2 access and L3 routed access nodes, requiring no topology changes for implementation.
Initially introduced in IOS XE 17.3.2a with a downtime of under 30 seconds, xFSU has been further enhanced in IOS XE 17.15.2 release, reducing downtime to less than 5 seconds to meet the demands of endpoints with aggressive timers.
xFSU supports software upgrades and reloads for specific IOS XE releases, including upgrades within EM releases, upgrades between EM releases, and reloads across both SM and EM releases.
Note: Minimum licensing requires Network Essentials for standalone switches and Network Advantage for stacked switches.
Tying all this together, xFSU offers a comprehensive coverage of all 9300 access use cases, thereby enabling seamless operation in mission-critical environments, thanks to its less than 5 second downtime during upgrades and reloads - now available from IOS XE 17.15.2 with enhancements! See the difference for yourself now!
For more details, please refer: Performing Extended Fast Software Upgrade (xFSU)
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