This read-only INTEGER, used together with ciscoWANPnniRemoteNodeId, indicates that the reachability of a specific remote PNNI node has changed, either ok(1) meaning it became reachable or fail(2) meaning it became unreachable. An administrator uses this to be notified when routing reachability to a specific remote node flips, which can explain sudden call-setup failures toward that node's addresses. For example, ciscoWANPnniReachability reporting fail(2) for the remote node identified in ciscoWANPnniRemoteNodeId explains why new SVC setup attempts toward addresses behind that node are now failing.