问答题 port-security的restrictaction是什么意思？
问答题 spanning-tree关于listeningandlearningtime如何adjustandchangeamountoftime？
问答题 WhichOSPFnetworktypeisidealforpartiallymeshedNBMAnetworksbecauseitiseasytoconfigure（requiresnoconfigurationofneighborcommands），consumesonlyoneIPsubnet，andrequiresnodesignatedrouterelection？