Switching, VLAN and spanning tree troubleshooting

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By the end you’ll be able to

Troubleshoot switch forwarding issues by interpreting MAC address table behavior, interface status, port roles and symptoms such as unknown destination flooding, intermittent loss and one-way communication.
Diagnose VLAN configuration problems, including incorrect access VLAN assignment, missing VLANs, disabled VLANs, voice VLAN issues and failed inter-VLAN communication when the fault lies in switching configuration.

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Interpret spanning tree states, roles and topology changes to isolate loops, unexpected blocking, root bridge misselection, slow convergence symptoms and broadcast storms.

Differentiate switching issues from routing or host issues by validating local segment behavior, ARP or neighbor discovery outcomes and same-VLAN versus different-VLAN reachability.

Verify remediation by confirming correct VLAN propagation, stable spanning tree topology, restored trunk operation and expected host connectivity across the switched domain.

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