Wehavealreadycoveredthetopicofnetworkaddresses.Thefirst(71)inablock(inclassesA,B,and C)definesthenetworkaddress.InclassesA,B,andC,ifthehostidisallls,theaddressiscalledadirectbroadcastaddress.Itisusedbya.()tosendapackettoallhostsinaspecificnetwork.Allhostswillacceptapackethavingthistypeofdestinationaddress.Notethatthisaddresscanbeusedonlyasa(73)addressinanlPpacket.NotealsothatthisspecialaddressalsoreducesthenumberofavailablehostidforeachnetidinclassesA,B,and C. InclassesA,B,andC,anaddresswithallIsforthenetidandhostid(32bits)definesa(74)addressinthecurrentnetwork.AhostthatwantstosendamessagetoeveryotherhostcanusethisaddressasadestinationaddressinanIPpacket.However,arouterwillblockapackethavingthistypeofaddresstoconfinethebroadcastingtothe(75)network.Notethatthisaddressbelongstoclass E. A.router
A.switch B.hu D.firewall正确答案A
