Which statement best describes BPDU guard and root guard on access ports?

Which statement best describes BPDU guard and root guard on access ports?

• A. BPDU guard disables a port that receives BPDUs; Root guard prevents a port from becoming a root port.
• B. BPDU guard prevents a port from becoming a designated port; Root guard disables a port that receives BPDUs.
• C. BPDU guard prevents root bridges from forming; Root guard guarantees a port will become designated.
• D. BPDU guard and root guard are identical in function.

Answer: (B)

On access ports, BPDU guard and root guard are safeguards that react to BPDUs to keep the topology stable. BPDU guard is aimed at edge ports that should not participate in STP. When a BPDU is received on such a port, it is immediately put into an error-disabled state, effectively preventing that port from forwarding or becoming a designated port. This is why describing it as preventing the port from becoming a designated port fits. Root guard serves a different purpose: it stops a port from becoming a root port. If the port receives a BPDU that suggests another switch should be the root (a superior root), the port is placed into a blocking/root-inconsistent state to halt that path from making this switch the root. In practical terms, that action is described as disabling a port that receives BPDUs. The other choices either mix up the roles or claim they’re identical, which isn’t accurate.

On access ports, BPDU guard and root guard are safeguards that react to BPDUs to keep the topology stable. BPDU guard is aimed at edge ports that should not participate in STP. When a BPDU is received on such a port, it is immediately put into an error-disabled state, effectively preventing that port from forwarding or becoming a designated port. This is why describing it as preventing the port from becoming a designated port fits.

Root guard serves a different purpose: it stops a port from becoming a root port. If the port receives a BPDU that suggests another switch should be the root (a superior root), the port is placed into a blocking/root-inconsistent state to halt that path from making this switch the root. In practical terms, that action is described as disabling a port that receives BPDUs.

The other choices either mix up the roles or claim they’re identical, which isn’t accurate.