Final answer:
The running-configuration file of a Cisco router is stored in RAM, which reflects immediate changes to the configuration but requires saving to NVRAM to be persistent across reboots.
Step-by-step explanation:
The running-configuration file for a Cisco router is stored in RAM (Random Access Memory).
This configuration file is active on the router and any changes made to the configuration are immediately reflected in the running-configuration stored in RAM. It is important to note that if the router is restarted without saving these changes to the startup-configuration, which is stored in NVRAM (Non-Volatile Random Access Memory), all changes will be lost. The startup-configuration is what the router uses to boot with every restart, ensuring persistence of configurations across reboots.