The real DESCRIPTION field here is just the auto-generated stub "Cisco UCS fabric:FcVsanPortEp:peerDn managed object property", so it carries no real prose -- but the property name and its SnmpAdminString type tell you what it holds: It holds the dn of the object on the far end of this VSAN port endpoint's connection -- effectively recording what the SAN switch port on the other end of that VSAN link. This is the field that lets UCS Manager (and anything polling this OID) trace a wire all the way through: given this VSAN port endpoint, you can look up peerDn to find exactly which switch, port, or port-channel object it is paired with, without having to cross-reference cabling diagrams by hand. For this VSAN port endpoint, peerDn might read something like fc-switch/slot-8/port-25, naming the specific device and port on the SAN side.