What is the command to save a Cisco router or switch configuration?

The command to save a Cisco router or switch configuration is indeed "copy running-config startup-config." This command is essential as it transfers the current running configuration, which resides in the router or switch's volatile memory (RAM), to the startup configuration stored in non-volatile memory (NVRAM). The startup configuration is what the device loads upon reboot, ensuring that all configurations are retained after a power cycle.

Using this command effectively makes sure that all changes made to the running configuration—such as interface settings, routing protocols, and other configurations—are preserved for future use. If the running configuration is not saved, any changes made will be lost when the device is restarted.

In the context of the other choices, some of them do not adhere to the correct syntax or functionality in Cisco IOS. For instance, "copy startup-config running-config" actually copies the saved configuration into the running configuration, which is the opposite of saving current changes. "save running-config startup-config" lacks the proper command syntax used in Cisco devices, as the correct method involves the 'copy' command. Lastly, "store config running-config" is not a valid command in the Cisco command set, as 'store' is not used in this context.

Therefore, the command "