What is the default OSPF reference bandwidth for calculations?

The default OSPF reference bandwidth for calculations is 100 Mbps. OSPF (Open Shortest Path First) uses this reference bandwidth to calculate the cost of routes within a network. The cost of an OSPF route is inversely related to the bandwidth of that link; a higher bandwidth results in a lower cost.

This default setting of 100 Mbps was chosen to suit most Ethernet networks, which typically operate at or above this speed. However, in scenarios where links with higher bandwidth (like 1 Gbps or faster) are common, network engineers may need to adjust the reference bandwidth to accurately reflect performance and optimize routing decisions. The flexibility to modify this value allows OSPF to accurately account for different link speeds, ensuring efficient routing paths are chosen based on actual bandwidth capabilities.

Understanding this concept is crucial for network design and troubleshooting, particularly as network speeds continue to increase and more sophisticated configurations are employed.