Whether it is a fresh new install or a software upgrade, these would be the time for you to also consider an EPLD upgrade. Unlike software upgrade where you can potentially avoid an extended downtime using In-Service Software Upgrade (ISSU), EPLD upgrade requires the hardware to be taken offline and, in some cases, even chassis reload. Since the EPLD version has to stay in sync with the NXOS version, depending on what version you are upgrading to, you might need to upgrade all the pieces of hardware, and these include all supervisors, linecards, fans, and fabrics, which can result in a significant downtime.
In this article, we will provide timing results from running tests between sequential and parallel EPLD upgrade. This is to give you some guideline and help you determine appropriate actions for your environment.