单项选择题 While troubleshooting a network connectivity issue, you suspect that a router may be missing a route, or may be receiving bad routing information to a destination. What command should you issue to view the route that the router will use to reach a given destination?（）

单项选择题 While logged into a router you manually shut down the serial 0 interface using the "shutdown" interface configuration command. You then issue the "show interface serial 0" command in exec mode. What could you expect the status of the serial 0 interface to be?（）

单项选择题 There is a connectivity problem between the serial 0/0 interface of router TESTKING1 and the serial 0/0 interface of TESTKING2. A leased line point to point circuit is installed between these two routers. The output from the "show interface serial 0/0" command is displayed below for each of these routers: From your observations of the above exhibit, what is the underlying cause of the problem?（）