Practice Test GeeksCisco CCNA Practice Test
← All Cisco CCNA Flashcard Decks

Spanning Tree Protocol (STP) Flashcards

7 cards from real Cisco CCNA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Spanning Tree Protocol (STP) flashcards as text

  1. Which STP feature prevents a port connected to a non-root switch from becoming a root port and thus prevents root bridge changes?

    Answer: Root Guard

    Root Guard enforces the root bridge placement by putting a port in root-inconsistent state if a superior BPDU is received on it.

  2. How does RSTP achieve faster convergence compared to traditional 802.1D STP?

    Answer: RSTP uses a proposal/agreement handshake mechanism between neighboring switches

    RSTP's proposal/agreement mechanism allows ports to synchronize and transition to Forwarding without waiting for timers to expire.

  3. What STP port cost is assigned to a 100 Mbps Fast Ethernet link using the original IEEE 802.1D-1998 cost table?

    Answer: 19

    The original 802.1D-1998 standard assigns a cost of 19 to 100 Mbps links; this is the default cost Cisco switches use.

  4. In STP, which switch port is elected as the designated port on each network segment?

    Answer: The port with the lowest cumulative path cost to the root bridge on that segment

    On each segment, the designated port is the one offering the best (lowest cost) path to the root bridge; if tied, the lower bridge ID wins.

  5. A switch port is stuck in the STP Blocking state and does not transition even after the network stabilizes. Which feature is most likely responsible?

    Answer: Root Guard placed the port in root-inconsistent blocking state

    Root Guard places a port in root-inconsistent (blocking) state when a superior BPDU is received; the port stays blocked until no more superior BPDUs arrive.

  6. Which command configures BPDU Guard globally on all PortFast-enabled ports on a Cisco switch?

    Answer: spanning-tree portfast bpduguard default

    The global command 'spanning-tree portfast bpduguard default' enables BPDU Guard on all ports that have PortFast configured.

  7. What is the purpose of the STP max age timer (default 20 seconds)?

    Answer: It defines how long a switch stores BPDU information before discarding it as stale

    If a switch does not receive a BPDU within the max age period (20s default), it assumes the path has failed and begins STP recalculation.