Cisco CCNA Spanning Tree Protocol (STP) 5

Question 1

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

Accepted Answer

Root Guard

Answer

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

Question 2

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

Accepted Answer

RSTP uses a proposal/agreement handshake mechanism between neighboring switches

Answer

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

Question 3

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

Accepted Answer

19

Answer

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

Question 4

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

Accepted Answer

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

Answer

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.

Question 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?

Accepted Answer

Root Guard placed the port in root-inconsistent blocking state

Answer

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.

Cisco CCNA Practice Test

Cisco CCNA Practice Test

Cisco CCNA Spanning Tree Protocol (STP) 5