问答题 spanning-tree关于listeningandlearningtime如何adjustandchangeamountoftime？
问答题 WhichOSPFnetworktypeisidealforpartiallymeshedNBMAnetworksbecauseitiseasytoconfigure（requiresnoconfigurationofneighborcommands），consumesonlyoneIPsubnet，andrequiresnodesignatedrouterelection？
问答题 WhichOSPFfeatureallowsaroutertocontinuetoforwardpacketswhileundergoingspecific，well-knownfailureconditions？