Basics and Concepts Flashcards
7 cards from real STP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Basics and Concepts flashcards as text
Which STP enhancement runs a separate spanning tree instance per VLAN on Cisco switches?
Answer: PVST+
Per-VLAN Spanning Tree Plus (PVST+) runs an independent STP instance for each VLAN, allowing load balancing across redundant links.
In STP, what does the 'port ID' consist of?
Answer: Port priority and port number
The port ID is an 8-bit priority (default 128) combined with the port number, used as a final tiebreaker in root port selection.
What is the STP behavior when two switches are connected by two parallel links and one switch is non-root?
Answer: One port becomes root port; the other is blocked
STP blocks one of the redundant ports on the non-root switch to eliminate the loop, keeping only the lowest-cost path active.
Which STP timer defines how frequently the root bridge sends BPDUs?
Answer: Hello time
The hello time (default 2 seconds) controls the interval at which the root bridge generates and sends configuration BPDUs.
What is the effect of configuring PortFast on a switch port?
Answer: The port skips Listening and Learning and goes directly to Forwarding
PortFast bypasses the 30-second STP convergence delay by moving end-device ports directly to the Forwarding state.
What is the Bridge Protocol Data Unit (BPDU) guard feature designed to do?
Answer: Shut down a PortFast port if it receives a BPDU
BPDU Guard err-disables a PortFast-enabled port if any BPDU is received, protecting the topology from rogue switches.
Which STP port state is responsible for populating the MAC address table but NOT forwarding data frames?
Answer: Learning
The Learning state allows the switch to populate its MAC address table from incoming frames without actually forwarding those frames.