多项选择题
Which three of these Metro Ethernet services map to E-Line services that are defined by the MEF?（）
A. Ethernet Private Line B. Ethernet Wire Service C. Ethernet Relay Service D. Ethernet Multipoint Service E. Ethernet Relay Multipoint Service
单项选择题 What is the recommended practice regarding UDLD when implementing it in all fiber-optic LAN ports?（）
多项选择题 Which two of these are recommended practices with trunks? （）
单项选择题 Why is STP required when VLANs span access layer switches?（）
