CompTIA Network+ (N10-009)Network ImplementationHard
A technician connects two switches directly together using a standard Ethernet patch cable instead of a crossover cable, and the link comes up successfully with no manual configuration. Which feature on modern switch ports allows this to work?
- AAuto-MDIX
- BLink Aggregation Control Protocol (LACP)
- CPower over Ethernet (PoE) negotiation
- DSpanning Tree Protocol (STP)
Show answer & explanationAnswer & explanation
Correct answer: A. Auto-MDIX
Auto-MDIX (Automatic Medium-Dependent Interface Crossover) allows a switch port to automatically detect the required pin configuration and internally swap transmit/receive pairs as needed, eliminating the historical requirement to use a crossover cable when connecting like devices such as switch-to-switch.
Why the other options are wrong
- B. LACP is used for bundling multiple links into an aggregate, unrelated to cable pinout detection.
- C. PoE negotiation determines power delivery classification, not signal pinout wiring.
- D. STP prevents Layer 2 loops but has no role in detecting cable pinout requirements.
Auto-MDIX
A feature on modern Ethernet ports that automatically detects and corrects for cable type (straight-through vs. crossover), allowing either cable type to establish a working link.
- Eliminates need to manually choose crossover vs. straight-through cables
- Standard on virtually all modern switches and NICs
- Historically required crossover cables for switch-to-switch or PC-to-PC links
Memory trick: Auto-MDIX is the port's 'auto-correct' for backwards wiring.