The correct answer is D. EPLD (Erasable Programmable Logic Device) upgrades on Cisco Nexus 9000 switches are separate from the Cisco NX-OS software upgrade process, including ISSU (In-Service Software Upgrade). Cisco documentation clearly states that EPLD upgrades are performed independently of NX-OS upgrades, meaning they are not automatically included as part of ISSU or standard system image upgrades.
EPLDs control low-level hardware functions such as ASIC behavior, port logic, and system components. Because of their hardware-centric role, upgrading EPLDs often requires manual intervention and may involve device reloads or module resets, depending on the platform and components affected.
Option A is incorrect because EPLD upgrades are typically performed sequentially per module, not simultaneously. Option B is incorrect because EPLD upgrades are not part of ISSU processes. Option C is incorrect because EPLD upgrades may cause service disruption, especially if a reload is required.
Therefore, the key defining feature is that EPLD upgrades are independent of the NX-OS ISSU process, making D the correct and verified answer.
