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352-001 · Question #364

Which two benefits does using virtual PortChannel technology provide? (Choose two).

The correct answer is A. vPC eliminates spanning-tree blocked ports. D. vPC uses all uplink bandwidth. Virtual PortChannel (vPC) eliminates STP-blocked ports by making dual-homed uplinks appear as a single logical bundle, and it uses all available uplink bandwidth because both switches forward traffic simultaneously in active-active mode.

Layer 2 Control Plane

Question

Which two benefits does using virtual PortChannel technology provide? (Choose two).

Options

  • AvPC eliminates spanning-tree blocked ports.
  • BvPC allows a dual-homed server to operate in active-standby mode.
  • CvPC significantly reduces latency.
  • DvPC uses all uplink bandwidth.
  • EvPC supports VLAN-based load balancing.

How the community answered

(27 responses)
  • A
    89% (24)
  • B
    4% (1)
  • E
    7% (2)

Why each option

Virtual PortChannel (vPC) eliminates STP-blocked ports by making dual-homed uplinks appear as a single logical bundle, and it uses all available uplink bandwidth because both switches forward traffic simultaneously in active-active mode.

AvPC eliminates spanning-tree blocked ports.Correct

vPC presents two physical Nexus switches as one logical port-channel peer to downstream devices, so spanning tree sees a single bundle rather than redundant paths requiring a blocked port - all member links remain in a forwarding state simultaneously.

BvPC allows a dual-homed server to operate in active-standby mode.

vPC enables active-active dual-homing where both uplinks forward simultaneously - active-standby is the opposite behavior and would negate the bandwidth and redundancy benefits vPC is designed to provide.

CvPC significantly reduces latency.

vPC is a redundancy and bandwidth aggregation technology and does not inherently reduce forwarding latency - any latency difference compared to a standard port-channel is negligible and not a primary benefit.

DvPC uses all uplink bandwidth.Correct

Because vPC operates in active-active mode with no blocked ports, traffic is hashed across all uplinks connected to both vPC peer switches, consuming the full aggregate bandwidth of all uplinks rather than only one active path.

EvPC supports VLAN-based load balancing.

vPC uses flow-based hash load balancing computed from source or destination MAC, IP address, or Layer 4 port fields - it does not perform VLAN-based load balancing across member links.

Concept tested: Cisco vPC active-active dual-homing benefits and STP elimination

Source: https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/configuration/guide/cli/CLIConfigurationGuide/vpc.html

Topics

#vPC#spanning tree#uplink bandwidth#Layer 2 multipath

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