Cisco 400-007 Dumps Questions Answers

B: Faster control plane convergence reduces the total recovery time after failure detection.

D: Enabling lower layer detection (such as BFD or physical layer link failure detection) shortens the time it takes to notify the control plane about link failure.

Why other options are incorrect:

A: Stability improves network operation but doesn’t address detection delay directly.

C: Interface flaps notification frequency doesn’t reduce initial detection delay — could actually create instability.

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D (Root Guard): Prevents unauthorized devices from becoming the STP root by blocking superior BPDUs on access ports.

E (BPDU Guard): Immediately shuts down ports that receive unexpected BPDUs, protecting against accidental or malicious connection of switches to access ports.

Why other options are incorrect:

A: Loop Guard protects against unidirectional link failures but not unauthorized devices.

B: PortFast speeds up STP convergence on access ports but does not provide security.

C: DTF (Dynamic Trunking Protocol) is not a security feature.

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C: Serialization delay is the time it takes to place a packet onto the physical medium.

E: It is calculated as (packet size / link speed), thus depending on both the packet size and the interface speed.

Why other options are incorrect:

A: It depends on both size and line rate, not just line rate.

B: Packet type has no effect on serialization delay.

D: It's not only packet size, but also link speed that affects it.

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