This is an internal identifier string UCS assigns to a reference tying a VM-FEX port-profile/network definition pushed from UCS to the network object actually created on the VMM to correlate it with its counterpart object on the external VMM. Because the Dn and name of that port-profile reference are meaningful only within UCS's own tree, this internal id is what UCS actually uses under the hood to match that port-profile reference up with the corresponding object it created or found on the VMM side. A value like '42' would have no meaning to a human admin browsing the VMM's own UI, but is exactly what UCS Manager's integration code looks up internally to confirm it's talking about the same object.