| Exam 400-101 | Question id=1171 | Layer 2 Technologies |
Which of the following statements is accurate regarding alternate ports?
| A. |
An alternate port is always in the forwarding state. | |
| B. |
An alternate port is the port on a switch that has the best path to the root bridge. | |
| C. |
An alternate port is the port on a segment that has the best path to the root bridge. | |
| D. |
An alternate port is a blocked port that receives more useful BPDUs from a port on another switch. | |
| E. |
An alternate port is a blocked port that receives more useful BPDUs from another port on the local switch. |
An alternate port is a blocked port that receives more useful bridge protocol data units(BPDUs) from a port on another switch. Rapid Spanning Tree Protocol (RSTP) defines the following four port roles:
- Root port
- Designated port
- Alternate port
- Backup port
The root port on a switch is the port that receives the best BPDU, which indicates the best path to the root bridge based on the best root port cost. All switches except the root bridge contain exactly one root port. Because there is only one best path to the root bridge, a switch can have only one root port; only the root bridge does not have a root port. Root ports are always in the forwarding state.
The best path to the root bridge is the one that has the lowest cost to the root bridge. The cost is based on the bandwidth of a link. The higher the bandwidth, the lower the cost.