200-301 Question #1368: Real Exam Question with Answer & Explanation

Question

What is the operating mode and role of a backup port on a shared LAN segment in Rapid PVST+?

Options

• Alearning mode and provides the shortest path toward the root bridge handling traffic away from
• Bblocking mode and provides an alternate path toward the designated bridge
• Cforwarding mode and provides the lowest-cost path to the root bridge for each VLAN
• Dlistening mode and provides an alternate path toward the root bridge

Explanation

In Rapid PVST+, a backup port on a shared LAN segment operates in a blocking mode to provide an alternate path towards the designated bridge.

Common mistakes.

• A. A learning port is preparing to forward but not yet forwarding traffic, and a backup port's role is not to provide the shortest path; that is the role of a root port.
• C. A forwarding port is actively sending/receiving traffic and is part of the active topology, whereas a backup port is explicitly in a blocking state.
• D. Listening mode is an intermediate state in traditional STP; in Rapid PVST+, ports transition more quickly or are primarily in blocking/forwarding states, and while it provides an alternate path, its operating mode is blocking.

Concept tested. Rapid PVST+ Port Roles

Reference. https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/12-2_55_se/configuration/guide/3750x_cg/sw_rstp.html

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