How do you disable a routing protocol on a Cisco device without removing the physical interface?

• A. Reload the router to disable protocols
• B. Enter the routing process in global config and use the shutdown command for that process
• C. Shutdown the interface
• D. Remove the routing protocol from the configuration

Answer: (B)

Routing protocols run as separate processes on Cisco devices, so you can stop one without touching any interfaces by shutting down that protocol’s process in its configuration. Enter global config, go into the protocol’s configuration mode (for example, router ospf 1), and issue the shutdown command. This halts the protocol, drops its adjacencies, and withdraws its learned routes, while leaving all physical interfaces up for other traffic. You can re-enable it later with no shutdown.

This is preferable to reloading the router (downtime), shutting the interface (disrupts that link), or removing the protocol from the configuration (removing and needing to re-add the protocol later). The shutdown approach keeps interfaces intact and provides an easy way to bring the protocol back up.