Cisco CCNA mock exam questions sample test – Question 93

Which switch port will be in a blocking state? (Click the Exhibit(s) button to view the switch port diagram.)

A. SwitchA Fa0/1
B. SwitchA Fa0/2
C. SwitchB Fa0/1
D. SwitchB Fa0/2

Correct Answer: D

SwitchB will be forwarding on F0/1, and blocking on F0/2.
SwitchA will become the STP root bridge due to its lower MAC address. All ports on the root bridge will become designated ports in a forwarding state. SwitchB has redundant
connectivity to the root bridge, and must block one of its interfaces to prevent a switching loop. STP will use its operations to determine which of the redundant interfaces on SwitchB
to block to prevent a switching loop
Both interfaces are the same speed (FastEthernet), and thus their cost to the root is the same.
Finally, the interface with the lowest number will become the forwarding port. F0/1 has a lower port number than F0/2, so F0/1 becomes a forwarding port, and F0/2 becomes a
blocking port.
Note: Unlike STP, Rapid Spanning Tree Protocol (RSTP) uses the term “discarding” for a switch port that is not forwarding frames.
LAN Switching Fundamentals
Describe and verify switching concepts
Cisco > Support > LAN Switching > Spanning Tree Protocol > Technology White Paper > Understanding Rapid Spanning Tree Protocol (802.1w) > Document ID: 24062