Examkin

Soru

Zorluk: Çok zorNetwork Cable Types and Connectors

A network technician is terminating a Cat 6 horizontal cabling drop from a patch panel to a wall jack. The patch panel end is wired according to the T568A pinout standard. During installation at the work area, the technician inadvertently wires the wall jack using the T568B pinout standard. A desktop computer is then connected to the wall jack using a standard T568B straight-through patch cable, and the patch panel port is connected to a switch port where Auto-MDIX (Automatic Medium-Dependent Interface Crossover) is explicitly disabled. Which of the following best describes the resulting physical layer connection state?

  1. No physical link will be established because the transmit and receive pin pairs are swapped between the MDI switch port and the MDI-X network interface card.Cevap
  2. B
    The connection will operate normally at Gigabit speeds because 1000BASE-T automatically uses all four wire pairs bidirectionally and ignores pinout color standards.
  3. C
    The link will establish and function, but severe near-end crosstalk (NEXT) will cause the switch port to continuously drop packets.
  4. D
    The link will fall back to a 100 Mbps half-duplex connection utilizing only wire pairs 1 and 4 for transmission.

Cevap

No physical link will be established because the mismatched wiring creates a crossover cable between a switch and a workstation, and Auto-MDIX is disabled.
Wiring T568A on one end of a cable and T568B on the other creates an Ethernet crossover cable by swapping wire pair 2 (orange) and wire pair 3 (green). Standard network deployment between different device types (e.g., a switch port and a desktop workstation NIC) requires a straight-through cable layout. When a crossover cable is inserted into this path and the switch port has Auto-MDIX disabled, the transmit pins of the NIC connect directly to the transmit pins of the switch port, and receive connects to receive. Consequently, signal synchronization fails completely and no physical link light or connection is established.

Adım Adım Çözüm

1
Analyze the pinout configuration of the horizontal cable drop.
One end is wired with T568A (Pair 2 on pins 3/6, Pair 3 on pins 1/2) and the other end with T568B (Pair 2 on pins 1/2, Pair 3 on pins 3/6).
Wiring T568A on one end and T568B on the other creates an Ethernet crossover cable.
2
Evaluate the device interface types and Auto-MDIX status.
Connecting a switch port (MDI-X) to a network workstation interface (MDI) normally requires a straight-through cable.
Straight-through cables connect transmit pins on one device to receive pins on the other device.
3
Determine the impact of using a crossover cable without Auto-MDIX.
The crossover cable swaps pins 1/2 with pins 3/6. Combined with the MDI to MDI-X port crossing, transmit pins connect directly to transmit pins and receive pins connect to receive pins.
Without Auto-MDIX to electronically reassign the port pins, signals cannot be received by either end, resulting in complete link down (no physical connection).

Anahtar Kavram

T568A/T568B Wiring Standards & MDI/MDI-X Crossover Rules
Bu soruyu puanla

Konular

Network Cable Types and Connectors

Bu konudan daha fazla soru