Cisco Certified Network Associate (CCNA) Practice Exam 2025 - Free CCNA Practice Questions and Study Guide

The function of the virtual router backup in the Virtual Router Redundancy Protocol (VRRP) is to take over if the virtual router master fails. In a VRRP setup, multiple routers coordinate to present themselves as a single virtual router. The primary or master router handles the actual traffic, while the backup routers monitor its status.

If the master router becomes unavailable due to a failure, the backup router steps in and assumes the role of the master. This ensures continuous availability of routing services and minimizes downtime, which is crucial in maintaining network reliability. The backup router periodically checks the health of the master. If it detects that the master is no longer responsive, it promptly takes over as the new master, facilitating a seamless transition for network traffic.

This redundancy allows for high availability in network designs, as it prevents a single point of failure from affecting overall network performance. In summary, the primary role of the virtual router backup is to enhance the reliability and availability of the network by taking action when the primary router is down.