The statement that is true about the impact of a rolling EPLD upgrade on a Cisco MDS 9000 Series Switch is that only the modules that are being upgraded are disrupted. A rolling EPLD upgrade is a type of EPLD upgrade that allows the user to upgrade one or more modules in a switch without affecting the rest of the modules. The rolling EPLD upgrade requires a module reload for each module that is being upgraded, which causes a temporary disruption of traffic and services on that module. However, the other modules in the switch continue to operate normally and do not require a reload. The other statements are not true because:
* All modules on the switch are not disrupted. As explained above, only the modules that are being upgraded are disrupted, while the other modules are unaffected by the rolling EPLD upgrade.
* An EPLD upgrade is not nondisruptive. An EPLD upgrade is a process that updates the firmware of the electrical programmable logic devices (EPLDs) that provide hardware functionalities in the switch modules. An EPLD upgrade always involves a module reload, which causes a disruption of traffic and services on that module. However, the disruption can be minimized by using the hitless or non-disruptive EPLD upgrade modes, which preserve the forwarding state and configuration of the module during the reload.
* The upgrade cannot be performed from the standby supervisor module. The EPLD upgrade process requires the supervisor module to be in active mode before it can be upgraded. The standby supervisor module must be switched to active mode manually or automatically before the upgrade can begin.
References: For more information on how to perform a rolling EPLD upgrade on a Cisco MDS 9000 Series Switch, please refer to the following resources:
* Cisco MDS 9000 Series EPLD Release Notes, Release 8.4(1)
* Cisco MDS 9000 Series NX-OS System Management Configuration Guide