An Ethernet cable is attached to a PC NIC and then attached to a switch port. The PC power is turned on and the switch port link LED turns green. The link light indicates what two conditions?…

Question

Options

• ALayer 2 communication has been established between the PC and switch.
• BThe PC has received a DHCP address.
• CTraffic is being sent from the switch to the PC.
• DIf flashing, the green LED indicates port speed of 100 Mb/s.
• EThe Layer 1 media is functioning between the PC and switch.
• FThe switch port is functioning as a half-duplex connection.

• A
  95% (53)
• B
  2% (1)
• C
  4% (2)

Explanation

A green link LED confirms two things simultaneously: the physical medium (cables, connectors, NIC hardware) is functioning correctly at Layer 1, and the switch has successfully completed the Layer 2 link negotiation with the NIC - including auto-negotiation of speed and duplex - meaning Layer 2 communication is established. Both A and E are correct because a green link light requires both layers to be working.

The distractors fail for specific reasons: B is wrong because DHCP is a Layer 3/application process entirely separate from link state; C is wrong because a solid green LED means the link is up, not that traffic is flowing (flashing typically indicates activity); D is wrong because flashing green indicates traffic, not port speed (speed is usually shown via a separate LED or LED color scheme); F is wrong because the link LED gives no indication of duplex mode.

Memory tip: Think of the green LED as a "road is built and open" signal - it confirms the physical road exists (Layer 1) and vehicles are legally authorized to use it (Layer 2 link established), but it tells you nothing about whether cars are currently driving (traffic), the speed limit (port speed), or whether anyone has a GPS address yet (DHCP).

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