Ensuring that data is transmitted securely over an IP network is the main purpose of：（）

单项选择题WhichofthefollowingisSTPBESTidentifiedbyunderthecablesheath？（）

A.Number of twists in wires
B.Number of wires
C.Lubricant
D.Foil

多项选择题Whichofthefollowingwouldbeconsideredaroutingprotocol？（）

A.OSPF
B.DHCP
C.SMTP
D.SNMP
E.RIP

单项选择题WhichofthefollowingnetworkservicesisresponsibleformappingnamestoIPaddresses？（）

A.DHCP
B.DNS
C.IMAP4
D.Telnet

单项选择题Whenoneconnectiontoahostfailsinafullmeshnetwork，whichofthefollowingistrue？（）

A.All hosts can communicate.
B.No hosts can communicate.
C.Half of the hosts will lose communication.
D.Only the two hosts between the failed connection will lose communication.

单项选择题AuserconnectstothecompanysintranetserverviaaVPNconnectionfromasmalloffice homeoffice（SOHO）usingthebroadbandservice.Oneday，theusercannotsuccessfullyconnecttotheVPNandreceivesanerrormessagethatstates Usernameandpasswordareinvalidonthedomain. Whichofthefollowingshouldbedonetocorrectthisproblem？（）

A.Call the corporate help desk to have the VPN server rebooted
B.Re-enter the username and password in the VPN connection and reconnect
C.Call the broadband Internet provider to replace the SOHO router with a newer model
D.Ping the corporate VPN server to ensure it is online