单项选择题
A. to provide service internetworking
B. to support transparency for Layer 2 frames
C. as a connection identifier to indicate destination
D. as a mapping to the DLCI in service internetworking
E. to provide a trunk by which all VLANs can navigate from one site to one or multiple sites
单项选择题 Your MPLS implementation is currently using internal backdoor links. What can you do to minimize the impact of having these links?（）
多项选择题 Which two of these are characteristics of MPLS VPNs?（）
单项选择题 Which of these technologies is characterized as being a multipoint Layer 2 VPN that connects two or more customer devices using Ethernet bridging techniques?（）