Link Flapping

What is link flapping?

Link flapping happens when an Ethernet port keeps going up and down, connecting and disconnecting over and over. Each time the link drops, traffic stops for a moment while the port renegotiates the connection. If this happens dozens or hundreds of times, the result is a connection that feels unreliable and choppy.

Imagine a light switch that keeps flickering on and off. The light technically "works," but you would not call it reliable. Link flapping is the networking equivalent: the port never stays connected long enough to provide a stable experience.

Why it matters

Every time a link flaps, devices connected through that port lose connectivity for a brief moment. This causes video calls to freeze, file transfers to restart, and web pages to stall. If the flapping is fast enough, your computer might not even report a disconnection, but you will notice the dropouts.

Link flapping can also confuse your router and switch. Each time a port comes back up, the switch has to relearn which devices are connected to it. On busy networks, rapid flapping can generate enough overhead to slow down other ports too.

What you can do

• Check the Ethernet cable for visible damage: kinks, crushed sections, chewed spots (pets love network cables), or connectors that are cracked
• Replace the cable with a known good one; this is the single most common fix for link flapping
• Make sure the cable is fully seated in the port; a loose connection can cause intermittent drops
• If the cable runs near power lines, fluorescent lights, or electrical motors, try rerouting it; electromagnetic interference can cause flapping
• Try a different port on the switch or router to rule out a faulty port
• If the problem only happens when the cable is moved or touched, the connector or cable is damaged and needs to be replaced

What Network Weather shows you

Network Weather tracks how often each port's link state changes. Frequent changes indicate an unstable connection that needs attention.