单项选择题
A.Upgrade the switches
B.Configure BPDU guard
C.Configure VLAN access lists
D.Configure port security
E.Configure Dynamic ARP inspection
单项选择题 TworoutersconfiguredtorunBGPhavebeenconnectedtoafirewall，oneontheinsideinterfaceandoneontheoutsideinterface.BGPhasbeenconfiguredsothetworoutersshouldpeer，includingthecorrectBGPsessionendpointaddressesandthecorrectBGPsessionhop-countlimit（EBGPmultihop）.WhatisagoodfirsttesttoseeifBGPwillworkacrossthefirewall？（）
多项选择题 Youarethenetworkadministratorofamedium-sizedcompany，andusersarecomplainingthattheycannotsendemailstosomeorganizations.Duringyourtroubleshooting，younoticethatyourDNSMXrecordisblacklistedbyseveralpublicblacklistfilters.AfterclearingtheselistingsforyourIPaddress，andassumingthatyouremailserverhastherightvirusprotectioninplace，whataretwopossiblesolutionstopreventthisfromhappeninginthefuture？（）
单项选择题 Whiledeployinganewswitch，youaccidentlyconnectports3/12and3/18together，creatingaloop.STPdetecteditandplacedport3/18inblockingmode.WhydidSTPnotplaceport3/12inblockingmodeinstead？（）