What happens when the root bridge receives a configuration BPDU containing superior information?

Question

Options

• AThe root bridge ignores the superior BPDU.
• BThe root bridge updates its own configuration BPDU and sends it out all designated ports.
• CThe root bridge recalculates the spanning tree.
• DThe root bridge forwards the superior BPDU out of all designated ports.

• A
  88% (46)
• B
  2% (1)
• C
  2% (1)
• D
  8% (4)

Explanation

By definition, the root bridge has the lowest Bridge ID in the spanning tree domain and is the authoritative source of configuration BPDUs. When the root bridge receives an incoming configuration BPDU, it compares that BPDU against its own information. Because no other bridge can have a bridge ID lower than the root bridge's, any incoming BPDU cannot truly be superior under normal STP operation - the root bridge will not update its own root information based on incoming configuration BPDUs. It ignores the BPDU and continues to originate its own configuration BPDUs out all designated ports unchanged.

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