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

The cost of a 10 Gbps interface according to the IEEE 802.1D Spanning Tree Protocol (STP) is 2. STP uses path costs to determine the best path for data to travel through a network while preventing loops. These costs are determined based on the bandwidth of the interfaces.

In the case of a 10 Gbps interface, the cost is calculated based on a specific formula defined in the STP standard. This formula provides a cost assignment that allows devices to compare paths effectively. A higher bandwidth results in a lower cost value, which then allows the STP protocol to prefer interfaces with higher speeds over lower-speed ones.

For instance, Ethernet interfaces have the following path costs according to their respective speeds:

• 10 Mbps: 100

• 100 Mbps: 19

• 1 Gbps: 4

• 10 Gbps: 2

This system of cost assignment helps ensure efficient data flow across the network while maintaining a loop-free topology. Hence, for a 10 Gbps interface, the correct STP cost is 2.