Don't send jumbo ethernet frames to Roku devices.

The title summarizes it all.

I've had ethernet at home for 35 years (started with thinnet back in the day after getting rid of some Arcnet), and I've had jumbo frame support (8K to 9K frame length instead of the default 1518) for about a quarter century.

Never had a compatibility problem; things just work a little faster.  Until spring of 2026.

Multiple models of Roku streamers plugged into multiple models of Netgear managed prosumer ethernet switches, all experiencing the same symptom at about the same rate.  The switch logs the port drops and comes back up a second later, causing minor performance degradation to the Roku and spam in my ethernet switch logs.  I theorize it's renegotiating the autodetected port speed when it drops "enough" 9K ethernet frames.  I can lock my ethernet switch port to 100M speed; however I can't lock the Roku streamer port, and that's the device that, what I theorize, is demanding a speed renegotiation and bouncing the port.

I set the MTU to 1518 bytes, and all devices on all switches are now stable.

Wild to think in a quarter century the only hardware/firmware/software I've EVER owned that's incompatible with jumbo ethernet frames is Roku streamer boxes.

I posted it to the blog because it was a fun and satisfying problem to diagnose and fix, and I have no idea where to file a real bug report.  I won't deal with consumer grade customer support LOL.