What command is used to configure the OSPF reference bandwidth?

The command used to configure the OSPF reference bandwidth is indeed "auto-cost reference-bandwidth megabits-per-second." This command allows network administrators to set the reference bandwidth that OSPF uses to calculate the cost of routes based on the interface speeds. By default, OSPF uses a reference bandwidth of 100 Mbps. However, in modern networks, especially those using higher-speed links, you may want to adjust this reference bandwidth to better reflect the speeds of your network interfaces, ensuring that OSPF makes optimal routing decisions.

When configuring OSPF, the reference bandwidth is a crucial parameter because OSPF uses it in conjunction with interface bandwidth to compute costs, impacting the overall routing metrics. Setting this parameter correctly can lead to better performance in OSPF route calculations and ultimately more efficient routing within the network.

The other commands listed do not accurately reflect valid OSPF commands recognized by Cisco devices for configuring reference bandwidth. Some may resemble valid configurations for other contexts but do not apply to OSPF. Thus, understanding the proper syntax of Cisco IOS commands is essential for successful network configuration and management.