vpc

If you are familiar with Nexus vPC configuration, you might have been setting different STP priority on the primary and secondary switches so the primary is always a STP root, and have that lined up with, for example, HSRP active node. With vPC+ (ie. running vPC on a pair of switches that participate in fabricpath), the two Nexus switches appear as a single logical switch to both fabricpath cloud and upstream/downstream vPC switches, so it is actually crucial to make sure the upstream/downstream vPC switches receive consistent STP root priority regardless of which path is active. In this article, we demonstrate the importance of setting identical STP priority on the vPC+ peer switches, how the switches react when a superior BPDU is received, and other implications using Cisco Nexus 5000.

When you configure vPC on Cisco Nexus switches, vPC keepalive link is used by the two vPC peers to detect the liveliness of each other. The vPC keepalive plays a critical role of resolving a dual-active (aka split brain) scenario when the vPC peer link is down. This article presents different interface options of configuring vPC keepalive link on Nexus 5000 and discusses their pros and cons.