CISCO GSR routers do loopback testing, steps and configuration specific how to do, please help, thank you Be careful：

  Show Controllers Pos x/y,This command can only check the received light power is how much, can't see luminous power module, the premise is can't run power test, for help, thank you

Ping destination address for routing table, traceroute destination address also find routing table, but sometimes can ping pass traceroute impassability, please explain why, that is the way to the way back, will appear above, please explain in both r...

   ping 目标地址找路由表，traceroute 目标地址也找路由表，但是有时候能ping通traceroute不通，请解释为什么，也就是去的路跟回来的路不一样，就会出现上述情况，请解释下两者在路由表查找有那些异同。