单项选择题
You work as a network engineer， do you know an IPsec tunnel is negotiated within the protection of whichtype of tunnel？（）
A.L2F tunnel B.L2TP tunnel C.GRE tunnel D.ISAKMP tunnel
单项选择题 Forthefollowingitems，whichmanagementtopologykeepsmanagementtrafficisolatedfromActualTests.comproductiontraffic？（）
单项选择题 Whichdescriptionaboutasymmetricencryptionalgorithmsiscorrect？（）
单项选择题 Forthefollowingitems，whichonecanbeusedtoauthenticatetheIPsecpeersduringIKEPhase1？（）
