Commands to Monitor Interfaces on Junos Devices
You’ll often want to look at how your interfaces are behaving to figure out what is happening to the traffic within your device. As such, you need to become an expert in the show interfaces command.
As with all show commands, this command has several variations:
show interfaces (no modifier): The show interfaces command, issued with no modifier, gives you a summary of some of the most important fields and counters tracked for interfaces. This command is an excellent starting point for most interface activities.
show interfaces brief: The brief version of the same command pares down the output even more. This command is useful when you’re looking for big things such as whether an interface is up. If you need detailed statistics or counters, you must delve a little deeper than the brief command.
show interfaces detail: The detailed output for show interfaces includes all the information from the previous commands, and it also includes detailed statistics about the interface, including the interface counters for packets and bytes, as well as queuing information, which is useful when you have class of service (CoS) configured.
class-of-service Show class-of-service (CoS) information
Which version of the command you use depends on your goal.