单项选择题
What is one of the reasons that custom QoS ACLs are recommended over automatic QoS when configuring ports on a Catalyst 6500 for use with IP phones？（）
A. 79xx IP phones do not automatically mark voice packets with non-zero DSCP values.
B. 79xx IP phones do not mark protocol packets such as DHCP， DNS， or TFTP with non-zero DSCP values.
C. 79xx IP phones do not mark voice packets with optimal DSCP values.
D. 79xx IP phones use a custom protocol to communicate CDP information to the switch.
相关考题
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单项选择题
VLANTagging，alsoknownasFrameTagging，isamethoddevelopedbyCiscotohelpidentify packetstravellingthroughtrunklinks.WhenanEthernetframetraversesatrunklink，aspecial VLANtagisaddedtotheframeandsentacrossthetrunklink.HowdoesERSusetheVLANtag？（）
A. provide service internetworking
B. support transparency for Layer 2 frames
C. indicate destination as a connection identifier
D. map to the DLCI in service internetworking -
单项选择题
WhichofthesestatementsbestdescribesVPLS？（）
A. Neither broadcast nor multicast traffic is ever flooded in VPLS.
B. Multicast traffic is flooded but broadcast traffic is not flooded in VPLS.
C. VPLS emulates an Ethernet switch， with each EMS being analogous to a VLAN.
D. Because U-PE devices act as IEEE 802.1 devices， the VPLS core must use STP.
E. When the provider experiences an outage， IP re-routing restores PW connectivity and MAC re-learning is needed. -
多项选择题
WhichtwobenefitsdoesVoFRprovide？（）
A. bandwidth efficiency
B. cell-switching
C. congestion notification
D. heterogeneous network
