单项选择题
Which command displays the results of a loopback test you executed on a CT3 line module in slot 5, port 0, t1 number 4?（）
A.A B.B C.C D.D
Which command is used on the local router to invoke a l...
Which command is used on the local router to invoke a loopback mode on a remote ERX Edge Router?（）
Which command prompts an ERX Edge Router to go into a l...
Which command prompts an ERX Edge Router to go into a loopback mode on T1 number 1 when a command is received from a remote ERX Edge Router?（）
Which control expression must be the last line in all m...
Which control expression must be the last line in all macros?（）
