mscVrPpSrsePortNum 1.3.6.1.4.1.562.36.2.1.100.3.10.10.1.5

This attribute is indicative of the unique number assigned to the bridge port. It is used for SNMP management of this bridge port and in spanning tree as an identifier this bridge port. Notes regarding portNum: Escape routines exist for initializing, copying, and deleting port numbers. This is necessary because SNMP requires a unique port instance identifier. The initPortNum escape routine sets the port number to a value in the range 1-255 for this purpose. The setCopiedPortNum escape routine exists to maintain the uniqueness of the port number in cases when one port is copied to another. When a bridge port is deleted, the releasePortNum escape routine places the port number being released into a pending deletion state. This is because the port number cannot be re-allocated until the port is truely deleted in the current view. This is necessary since there is no guarantee of order when processing changes to multiple protocol ports so without the pending deletion state, the same port number could be temporarily assigned to two ports for a short period of time. The portNum is set as component critical since bridging also uses the port number as a key for indexing into its data structures. If a port is deleted then re-added under the same protocol port, CAS treats the change as a SET to the portNum attribute.