Big packet loss (up to 40%) after switching to Pi4

[cpunk]

So I had 3 separate Pi3 computers on a LAN made of Cat5 Ethernet cables and a home router. One was a WWW server, another an API server, third one a DB server.

I upgraded them to Pi4 and now I observe great packet loss, extending up to 40% of pings. All three exhibit this effect. SSH barely works but running "apt-get update" usually times out after some megabytes. Effect also occurs on LAN only and besides, my internet connectivity is fine (I'm posting this over the same connection).

Suspicions:
- power supply cables (they are powered via thin cables from a common 5V 8A supply to their GPIO power pins)
- gigabit ethernet issues (maybe they're trying to operate on gigabit speeds, but my router or cables don't support that)

Excluded:
- IPv6 seems unrelated, I tried disabling it an nothing changed

Has anyone encountered similar issues, or can anyone please tell how to force a Pi4 ethernet adapter to 100 Mbit speed?

[cpunk]

P.S. I also get big packet loss when I bring up a WiFi interface on a Pi and then try to ping it from my laptop on the same LAN. Pinging the router has 0% packet loss, pinging the Pi has 40%.

Ping times are around 2 ms in both cases.

[cpunk]

Until now, I have found no cure for this.

I switched over to WiFi however and left the Ethernet cables unconnected. Now, packet loss is 0%, but it's WiFi... it's not a long term solution for me. Will try to find a known-good gigabit switch to test with.

[sniegu.pl]

I have the same problem with my ISP's Cisco (docsis) router. About 40% packets droped to gateway directly connected via Ethernet cable.

Forcing the link to be 100M instead of 1G fixes this for me. Seems that there is some problem with 1G in my setup.

Forcing the link to 100Mbps:

Code: Select all

# ethtool -s eth0 speed 100 duplex full