Which command would you use to find a router's uptime?

The command to find a router's uptime is "show system uptime." This command is specifically designed to display how long the router has been running since it was last rebooted. Uptime is a crucial metric for network devices, as it provides information on the stability and reliability of the device over time. Using the "show system uptime" command will return the total operational time, which can help network administrators assess the health of the device and schedule maintenance if necessary.

Other commands provided do not yield uptime information as effectively or at all. For instance, "show system status" focuses on the overall system state but does not explicitly present uptime. "Display uptime information" and "check uptime" are not valid Junos commands for retrieving uptime data on Juniper devices, which makes them less relevant in this context.