关于帧中继的排错题WhentroubleshootingaFrameRelayconnection,whatisthefirststepwhenperformingaloopbacktest?A.SettheencapsulationoftheinterfacetoHDLC.B.PlacetheCSU/DSUinlocal-loopmode.C.Enablelocal-loopmodeontheDCE

Question

关于帧中继的排错题
When troubleshooting a Frame Relay connection,what is the first step when performing a loopback
test?
A.Set the encapsulation of the interface to HDLC.
B.Place the CSU/DSU in local-loop mode.
C.Enable local-loop mode on the DCE Frame Relay router.
D.Verify that the encapsulation is set to Frame Relay.
Answer:A请问为什么不选D呢?为什么帧中继排错第一步不是去验证封装是否正确,而是直接把封装类型改为HDLC了呢?是不是帧中继的封装不能做环回测试呢?请给出较详细的回答,

Answer 1

loopback 测试,就是测试本地接口.这个题,可以理解为,FR环境中,如果想ping本地LMI 要怎么办.当然是先把封装改成HDLC了,因为,封装成FR ping 本地是不通的.看题目最后 performing a loopback test?
环回测试 意思是本地的
显然A
hdlc 是只定义本地意义的!就是DTE到贞中继交换机之间.