What is the 802.1D STP cost for a 10 Mbps interface?

The Spanning Tree Protocol (STP) uses a cost metric to determine the best path for data to travel through a network. The cost of an interface is inversely related to its bandwidth; the higher the bandwidth, the lower the STP cost.

For a 10 Mbps interface, the cost is defined according to the formula typically used in STP calculations, which is based on the bandwidth. The cost for 10 Mbps is set to 100 in the IEEE 802.1D standard. This means that when STP evaluates paths to determine the best forwarding route, a 10 Mbps interface contributes a cost of 100, reflecting its limited throughput compared to faster interfaces.

Thus, when assessing the available choices, the correct value for a 10 Mbps interface is 100, aligning with the standardized metrics for link costs in Spanning Tree Protocol implementations.