Refer to the exhibit． Which statement describes DLCI 17?

A、 DLCI 17 describes the ISDN circuit between R2 and R3．
B、 DLCI 17 describes a PVC on R2． It cannot be used on R3 or R1．
C、 DLCI 17 is the Layer 2 address used by R2 to describe a PVC to R3．
D、 DLCI 17 describes the dial-up circuit from R2 and R3 to the service provider．

【正确答案】 C

【答案解析】DLCI是在Frame-relay中的描述二层信息的地址，他的地位等同于以太网中的MAC地址。我们以R2上的DLCI 17来看，DLCI 17描述的是：从这个接口出去的目的地为R3的接口的这条PVC的二层的地址为17。