Home » Cisco » 300-115 » How quickly can a non-edge port discover that its neighbor is down?
With RSTP hello timers set to the default interval, how quickly can a non-edge port discover that its neighbor is down?
A. 20 seconds
B. 10 seconds
C. 6 seconds
D. 5 seconds
Correct Answer: C
Explanation/Reference:
Answer:
With Rapid Spanning Tree Protocol (RSTP) hello timers set at the default interval, a non-edge port can discover that its neighbor is down in 6 seconds. One of the advantages of RSTP over STP is quicker convergence when changes occur in the topology. After a non-edge port fails to receive three Bridge Protocol Data Units (BPDUs) from its neighbor, it will assume the neighbor to be down and will age out all information regarding the neighbor. Since hellos are sent at 2second intervals in RSTP, it will take only 6 seconds for this to occur, as compared to 20 seconds for STP.
All other options are incorrect values for the default convergence time for RSTP.
Objective:
Layer 2 Technologies Sub-Objective:
Configure and verify spanning tree
References:
Cisco > Home > Support > Technology Support > LAN Switching > Spanning Tree Protocol > Technology Information > Technology White Paper > Understanding Rapid Spanning Tree Protocol (802.1w)
