You are the network administrator of a small Layer 2 network with 50 users. Lately， users have been complaining that the network is very slow. While troubleshooting， you notice that the CAM table of your switch is full， although it supports up to 12，000 MAC addresses. How can you solve this issue and prevent it from happening in the future？（）

单项选择题Whentroubleshootingtheissue，younoticetheelectionofanewrootbridgewithanunknownMACaddress.KnowingthatallaccessportshavethePortFastfeatureenabled，whatwouldbetheeasiestwaytoresolvetheissuewithoutlosingredundantlinks？（）

A.Enable bpduguard globally.
B.Enable rootguard.
C.Enable loopguard.
D.Enable spanning tree.
E.Enable UDLD

多项选择题Youarethenetworkadministratorofamedium-sizedcompany，andusersarecomplainingthattheycannotsendemailstosomeorganizations.Duringyourtroubleshooting，younoticethatyourDNSMXrecordisblacklistedbyseveralpublicblacklistfilters.AfterclearingtheselistingsforyourIPaddress，andassumingthatyouremailserverhastherightvirusprotectioninplace，whataretwopossiblesolutionstopreventthisfromhappeninginthefuture？（）

A.Change your Internet provider.
B.Change your public IP address.
C.Allow the email server to send traffic only to TCP port 25.
D.Put your email server in a DMZ.
E.Use a separate public IP address for your email server only.

单项选择题AfterapplyinganewACLonadevice，itsCPUutilizationrosesignificantlyandmanymessagesstartingwith %SEC-6-IPACCESSLOG appearedontheSyslogserver.Whatcanbedonetoresolvethissituation？（）

A.Increase memory allocation for ACLs.
B.Remove all entries from the ACL and use a single permit ip any any statement.
C.Remove the log keyword from each ACL entry.
D.Reboot the device after the ACL has been applied.

单项选择题WhichfeaturewouldpreventguestusersfromgainingnetworkaccessbyunplugginganIPphoneandconnectingalaptopcomputer？（）

A.IPSec VPN
B.SSL VPN
C.port security
D.port security with statically configured MAC addresses
E.private VLANs

多项选择题Yournetworkissufferingfromregularoutages.Aftertroubleshooting，youlearnthatthetransmitleadofafiberuplinkwasdamaged.Whichtwofeaturescanpreventthesameissuesinthefuture？（）

A.root guard
B.loop guard
C.BPDU guard
D.UDLD
E.BPDU skew detection