eFSU Operation
eFSU is an enhanced software upgrade procedure. Non-eFSU (FSU) software upgrades require system downtime, because a software version mismatch between the active and the standby supervisor engines forces the system to boot in RPR redundancy mode, which is stateless and causes a hard reset of the all modules.
eFSU enables an increase in network availability by reducing the downtime caused by software upgrades. eFSU does this by:
- Bringing up the standby supervisor engine in SSO mode even when the active and the standby supervisor engines have different software versions, or with VSS configured, when the supervisor engines in the two chassis have different software versions.
During an eFSU, new software is loaded onto the standby supervisor engine while the active supervisor engine continues to operate using the previous software. As part of the upgrade, the standby processor reaches the SSO Standby Hot stage, a switchover occurs, and the standby becomes active, running the new software. In previous releases Supervisor Engines running different software versions ran in the Route Processor Redundancy Mode.
You can continue with the upgrade to load the new software onto the other processor, or you can abort the upgrade and resume operation with the old software.
- Preloading new module software into memory on supported modules to avoid a hard reset.
If the new software release contains new module software, eFSU preloads the new module software onto any modules in the switch that support eFSU preload. When the switchover occurs between the active and standby supervisor engines, the modules are restarted with the new software image.
The WS-X67 xx modules modules support eFSU preload. All other modules undergo a hard reset at switchover, and the software image loads after the module restarts.
During a software upgrade, the switch performs the following steps automatically on modules that support eFSU preload:
– Reserves the necessary memory for the new Cisco IOS software image on each module.
– Preloads a new software image onto the modules as part of the issu loadversion command.
– Restarts the modules with the new software image when a switchover occurs (issu runversion).
– During the restart, the software features and routing protocols are not available.
– If a rollback or abort occurs, to minimize disruption, the switch preloads the original software version onto the module. Once the rollback or abort is completed, the module is restarted with the original software version.
Note All modules that support eFSU preload must have at least 512 MB of memory, with enough memory free to hold the new software image. If there is insufficient free memory, eFSU does not attempt the preload, but instead resets the modules during the switchover.
Reserving Module Memory
On modules that support eFSU, the supervisor engine automatically reserves memory on the module to store the new software image (decompressed format). The amount of memory needed varies according to the module type.
Although we do not recommend it, you can enter the following command to keep the switch from reserving memory for the software preload (where slot-num specifies which slot the module is installed in):
no mdr download reserve memory image slot slot-num
Note All modules that support eFSU preload must have at least 512 MB of memory, with enough memory free to hold the new software image. If there is insufficient free memory, eFSU does not attempt the preload, but instead resets the modules during the switchover.
To display whether or not the memory reservation was successful on a module, use the show issu outage slot all command See the “Displaying the Maximum Outage Time for Installed Modules (Optional)” section for a command example.