Ethernet LED Indicators and Duplexing Issues

Vocabulary-style flashcards covering NIC LED indicators (activity and link speed), switch LEDs, duplexing concepts (duplex mismatch, auto negotiation, full vs half duplex), collision domains, and common symptoms (runts).

Activity light (NIC LED)

Indicator on a NIC that shows link status and activity: off = no link, solid orange = link established with the upstream device (e.g., switch), blinking orange = data activity.

Link speed light (NIC LED)

Indicator of connection speed: green = 1 Gbps, orange = 100 Mbps, off = 10 Mbps.

Off activity light

No link or connection is established.

Solid orange activity light

A link has been established between the NIC and the upstream device (such as a switch).

Blinking orange activity light

Data activity is occurring on the link.

Duplex mismatch

A common duplexing issue where two ends negotiate different duplex modes (one full duplex, the other half duplex), causing performance problems.

Auto negotiate

Process by which two devices automatically determine speed and duplex; recommended to enable on both ends to prevent mismatches.

Full duplex

Mode where a device can transmit and receive simultaneously; typically used with switches; minimizes collisions.

Half duplex

Mode where a device can transmit or receive at a time; can lead to collisions in traditional Ethernet networks.

Collision domain

A network segment where simultaneous transmissions can collide; each switch port creates its own collision domain; using switches with full duplex reduces collisions.

Runts

Very small Ethernet frames (smaller than the 64-byte minimum) that can appear with duplex mismatch or other link problems.

Switch port LEDs

LEDs on each switch port that show the status and activity for quick port-by-port troubleshooting.