Cisco
352-001 · Question #516
352-001 Question #516: Real Exam Question with Answer & Explanation
The correct answer is C: REP is enabled on the port. REP (Resilient Ethernet Protocol) is a Cisco proprietary ring protocol that replaces STP and uses its own control mechanism instead of BPDUs, so no configuration BPDUs are exchanged even though the network operates normally.
Question
An operations engineer asks for your help with a new switching deployment. The engineer confirms that STP is enabled on an edge switch, and a particular port is connected to another switch. The switch is not receiving configuration BPDUs, although it appears that everything is functioning correctly in the network. What is the design explanation?
Options
- ABridge Assurance is enabled on the port
- BStorm control broadcast is enabled on the port
- CREP is enabled on the port
- DBPDU Guard is enabled on the port
Explanation
REP (Resilient Ethernet Protocol) is a Cisco proprietary ring protocol that replaces STP and uses its own control mechanism instead of BPDUs, so no configuration BPDUs are exchanged even though the network operates normally.
Common mistakes.
- A. Bridge Assurance requires BPDUs to be continuously exchanged on point-to-point links, and if BPDUs stop arriving, Bridge Assurance moves the port to a blocked inconsistent state - causing disruption rather than normal operation.
- B. Storm control broadcast limits the rate of broadcast traffic on a port but has no effect on BPDU transmission or STP operation, so it does not explain the absence of configuration BPDUs.
- D. BPDU Guard err-disables a port upon receiving a BPDU rather than suppressing BPDU transmission, and does not explain why configuration BPDUs are absent on a port connected to another switch.
Concept tested. Resilient Ethernet Protocol vs STP BPDU behavior
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