An engineer wants to implement a network with the RSTP+ but the majority of the equipment is running STP. What will be the outcome when running STP and RSTP+ simultaneously?

Question

Options

• ARSTP and STP will not work and the interface will be in error disabled
• BRSTP and STP will work and fast convergence will happen
• CRSTP and STP will work and fast convergence will not happen
• DRSTP and STP will choose the best convergence protocol

• A
  2% (1)
• B
  13% (7)
• C
  78% (43)
• D
  7% (4)

Explanation

RSTP (802.1w) is backward compatible with legacy STP (802.1D). When an RSTP switch detects that a neighboring switch is running legacy STP (via BPDUs), it falls back to legacy STP behavior on that specific port, using the slower 802.1D timers (hello = 2s, forward delay = 15s, max age = 20s). The network continues to function correctly - no ports go into error-disabled state - but the fast convergence benefit of RSTP is lost wherever legacy STP devices are present. There is no automatic selection of 'best convergence protocol'; RSTP simply degrades to STP behavior to maintain compatibility.

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