An active network link fails on an access switch operating under standard IEEE 802.1D Spanning Tree Protocol (STP). In what chronological order do the switches process and propagate this event across the switched network?
- 1The switch experiencing the link state change generates a Topology Change Notification (TCN) BPDU.
- 2The local switch transmits the TCN BPDU out its Designated/Root Port toward the Root Bridge.
- 3The upstream switch acknowledges receipt of the TCN BPDU by returning a Topology Change Acknowledgment (TCA) flag and forwards the TCN toward the Root Bridge.
- 4The Root Bridge receives the TCN BPDU and sets the Topology Change (TC) bit in its periodic Configuration BPDUs.
- 5Receiving switches temporarily shorten their MAC address table aging timer to flush stale forwarding entries.
Cevap
The correct chronological sequence begins with the local switch generating a TCN BPDU upon link failure, sending it upstream toward the Root Bridge, followed by intermediate switches acknowledging receipt with a TCA flag and forwarding the TCN upstream. Next, the Root Bridge receives the TCN and broadcasts Configuration BPDUs with the TC flag set, causing all switches in the network to temporarily reduce their MAC address table aging timer to flush stale entries.
The correct order follows the standard 802.1D Topology Change Notification mechanism: Local event detection and TCN generation -> Upstream TCN transmission -> Hop-by-hop TCA acknowledgment -> Root Bridge TC flag announcement -> Network-wide MAC table aging timer reduction.
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Anahtar Kavram
802.1D Spanning Tree Topology Change Notification (TCN) propagation and MAC aging timer adjustment