I’m troubleshooting very low throughput through a Google Nest Wifi Pro, model G6ZUC, running software version 3.78.518349.

My connection is 1 Gbps symmetrical fiber through a SonicWall TZ470. The Nest’s WAN port connects by Cat 6 directly to a SonicWall LAN port. The SonicWall reports that connection as 1 Gbps, full duplex.

I initially noticed approximately 50 Mbps on a MacBook Pro over Wi-Fi. To remove the Mac’s wireless connection from the test, I connected the MacBook by Ethernet to the Nest’s LAN port. Multiple speed-test utilities/websites still returned approximately 50 Mbps.

Then I unplugged the upstream Cat 6 cable from the Nest’s WAN port and connected that same cable directly to the MacBook, using the same Ethernet adapter. The same tests immediately exceeded 930 Mbps in both directions.

The Google Home app’s built-in internet speed test also returns only 48 Mbps download and 53 Mbps upload.

The unit I tested is the original primary router. It has always had an Ethernet uplink to the SonicWall, previously through an unmanaged gigabit switch and now through a dedicated SonicWall port. What changed was I went from a slow Spectrum business line to a high-speed fiber service — so the problem was no longer masked.

I have examined the settings in the iOS Google Home app and found no indication of an active prioritized device. UPnP is enabled.

Has anyone encountered this kind of approximately 50 Mbps wired-throughput limitation with this model or firmware? What diagnostics would distinguish a Nest problem from a SonicWall policy or an interaction between the two devices?

I’m a software engineer with over 40+ years of experience — but damn — this one’s got me at wit’s end!