Ethernet Cable Connections

Types of Ethernet Cables

Straight Through Cable

• Commonly used to connect ethernet devices.
• Pin configuration: Pin 1 to Pin 1, Pin 2 to Pin 2, etc.
• Also known as a patch cable.
• Used in wiring closets to connect patch panels to ethernet switches.
• Common for connecting workstations to network devices (e.g., switches).
• 10Base-T and 100Base-T Straight Through Cables:
  • Only two pairs of wires are used (pins 1, 2, 3, 6).

Gigabit Networking (1000Base-T)

• Uses all four pairs of wires in the cable.
• Both transmit and receive on every wire.
• Requires all eight wires to connect on both sides.
• Labeling: Data A, Data B, Data C, Data D.

Crossover Cable

• Used to connect similar devices (e.g., two workstations or two switches).
• 10/100Base-T Crossover Cable:
  • Pin 1 to Pin 3, Pin 2 to Pin 6, etc.
• 1000Base-T Crossover Cable (802.3 Standard):
  • All eight wires crossed over.
  • Specific pin-out not following TIA-568A/B standards.

Media Dependent Interface (MDI) and Media Dependent Interface Crossover (MDIX)

• MDI: Adapter inside a computer (Network Interface Card).
  • Pin 1: Transmit+, Pin 2: Transmit-, Pin 3: Receive+, Pin 6: Receive-.
• MDIX: Network switch interface.
  • Pin 1: Receive+, Pin 2: Receive-, Pin 3: Transmit+, Pin 6: Transmit-.

Auto-MDIX

• Modern Ethernet devices can automatically detect and configure connections (straight through or crossover).
• Eliminates the need for separate crossover cables.

Connection Scenarios

• Workstation to Switch (MDI to MDIX): Straight through cable.
• Router to Switch: Straight through cable.
• Switch to Switch (MDIX to MDIX): Crossover cable.
• Router to Router: Crossover cable.
• Workstation to Workstation: Crossover cable.
• Workstation to Router: Crossover cable (both MDI devices).

Clarifications on Crossover Cables

• Misconception: One side TIA-568A, other side TIA-568B.
• Reality: 1000Base-T crossover does not follow TIA-568A/B standards.
• Standard comes from IEEE 802.3 Ethernet standard.