A network with five switches has been configured to run Rapid Spanning Tree Protocol (RSTP)
with default settings. How many seconds does it take to detect a failure between two neighboring
switches?
A.
2 seconds
B.
3 seconds
C.
6 seconds
D.
15 seconds
Answer should be C (6 seconds)
http://www.juniper.net/documentation/en_US/junos12.1/topics/concept/spanning-trees-ex-series-rstp-understanding.html
To maintain the tree, the root bridge continues to send BPDUs at a “hello time” interval (default 2 seconds)
When an RSTP port does not receive a BPDU for three hello times, it reacts one of two ways. If the port is the root port, a complete rework of the spanning-tree occurs—see When an RSTP Root Bridge Fails. If the bridge is any non-root bridge, RSTP detects that the connected device cannot send BPDUs and converts that port to an edge port.
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Exactly correct: From the Juniper site: http://liner.link/eqQir
RSTP evolved from the original STP IEEE 802.1D protocol to providefaster spanning-tree re-convergence after a switch port, switch, orLAN failure. Where STP took up to 50 seconds to respond to topologychanges, RSTP responds to changes within the timeframe of three helloBPDUs (bridge protocol data units), or 6 seconds. This is the primaryreason that RSTP is the default configuration on EX Series switches.In addition, note that EX Series switches configured to use STP actuallyrun RSTP force version 0, which is compatible with STP.
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