STP Flashcards
What is the main purpose of Spanning Tree Protocol (STP)?
To prevent loops in a Layer 2 network
Which IEEE standard defines STP?
IEEE 802.1D
What are the five port states in classic STP?
Blocking Listening Learning Forwarding and Disabled
What is the default STP bridge priority?
32768
How does STP elect a root bridge?
The switch with the lowest bridge ID (priority + MAC address) becomes the root bridge
What happens if two switches have the same priority during root bridge election?
The switch with the lowest MAC address becomes the root bridge
What is the purpose of a root port in STP?
It is the port with the lowest cost path to the root bridge
How does STP calculate path cost?
By summing the cost of each link based on its bandwidth
Which port state listens for BPDUs but does not forward frames?
Listening
Which STP port role blocks traffic to prevent loops?
Alternate port
What is the purpose of the designated port in STP?
It forwards traffic toward downstream switches and has the lowest cost to the root bridge
What is the purpose of BPDU (Bridge Protocol Data Units) in STP?
To exchange information about topology and determine the best paths
What is the default STP Hello Timer interval?
2 seconds
What is the default Forward Delay timer in STP?
15 seconds
How does STP handle topology changes?
It temporarily reduces the aging time of MAC addresses to speed up convergence
Which STP enhancement helps prevent TCNs caused by frequent topology changes?
PortFast
What is the difference between STP and RSTP?
RSTP provides faster convergence by eliminating the listening state
Which IEEE standard defines Rapid Spanning Tree Protocol (RSTP)?
IEEE 802.1w
What STP feature prevents BPDUs from being received on an access port?
BPDU Guard
What STP feature prevents loops by placing inconsistent BPDUs on a port?
Root Guard
Which feature is used to limit the number of BPDUs a port can receive?
BPDU Filter
Which STP version supports multiple spanning tree instances?
MSTP (Multiple Spanning Tree Protocol)
What is the IEEE standard for MSTP?
IEEE 802.1s
What is the main advantage of MSTP over other STP versions?
It allows multiple VLANs to be mapped to the same spanning-tree instance
