In what situation must spanning-tree be implemented?

Question

Options

• AWhen redundant Layer 2 links, that are not part of a single EtherChannel or bundle, exist between
• BWhen redundant Layer 3 links, that are not part of a single EtherChannel or bundle, exist between
• CBetween Distribution and Core switches when interfaces are configured with "no switchport"
• DBetween Distribution and Core switches when VSS is configured

• A
  94% (46)
• B
  2% (1)
• C
  4% (2)

Explanation

Spanning Tree Protocol (STP) exists to prevent Layer 2 (Ethernet) broadcast storms and loops. It is required whenever redundant Layer 2 links exist between switches that are NOT part of an EtherChannel or port-channel bundle. EtherChannel bundles multiple physical links into a single logical link, so STP sees only one link and no loop is formed. Redundant Layer 3 links (B) do not create Layer 2 loops - routing protocols handle loop prevention at Layer 3. When interfaces are configured with 'no switchport' (C), they operate as routed (Layer 3) ports, eliminating the Layer 2 loop concern. VSS (Virtual Switching System) (D) makes two physical switches appear as a single logical switch, so redundant links between VSS members form a port-channel and no STP loop exists. Therefore, STP is mandatory only for redundant, unbundled Layer 2 links between switches.

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