Which command shows active configuration?

The show running-config command is used on Cisco IOS devices to display the configuration that is currently active in the device's Random Access Memory (RAM). This is the "live" or "active" configuration that dictates the device's current behavior. Any changes made via the command-line interface are immediately applied to the running configuration. This command is fundamental for verifying the current operational state and for real-time troubleshooting of the device's settings.

B. show startup-config: This command displays the configuration stored in Non-Volatile RAM (NVRAM). This is the backup configuration that is loaded into RAM when the device boots, not the currently active one.

C. show version: This command provides system information such as the IOS software version, hardware details, system uptime, and the configuration register value, but not the active configuration commands.

D. show ip route: This command displays the device's IP routing table, which is a dynamic table showing network paths. It is a result of the active configuration, not the configuration file itself.

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1. Cisco Systems, Inc., "Cisco IOS Configuration Fundamentals Command Reference," Document ID: a006878. In the chapter for "Show Commands," the description for show running-config states, "To display the contents of the current running configuration file... use the show running-config command in privileged EXEC mode." This confirms it shows the current, active configuration.

2. Cisco Systems, Inc., "Basic Device Configuration," Cisco IOS XE Gibraltar 16.11.x (Catalyst 9300 Switches) Software Configuration Guide. In the section "Managing Configuration Files," it is explained that the running configuration "resides in RAM" and the startup configuration "resides in NVRAM." The guide specifies using show running-config to view the active configuration.

3. University of Kentucky, College of Engineering, "Introduction to Cisco Router Configuration," Course materials for EE/CPE 588. Page 10, Section "Saving the Configuration." The document explicitly states: "The show running-config command will show you the configuration that is currently running on the router." It contrasts this with show startup-config, which shows the configuration stored in NVRAM.