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Up to 50% packet loss since days, only after gateway.

I am experiencing huge packet loss since a few days now and my ISP seems baffled and unable to fix the problem. First I thought it would be a damaged Ethernet cable in my LAN, but I checked the cable and also tested if the packet loss is happening on other OSes and hardware. It is persistent across Linux/Mac/Windows, Ethernet/WiFi and four different PCs.

I spoke twice with the disruption department of my ISP. They measured the connection/wire, found no indices of malfunction on the physical layer, I guess. The router had the strange behavior of losing the connection a few times an hour. Currently my ISP is still investigating, but they don't seem to solve this. So maybe there is something to see from my side.

I did the following to diagnose the problem:

  • Used MTR (Matt's Traceroute) on different IPs/Hosts.
  • Checked all LAN connected devices with MTR and ping. No losses in the LAN, including the gateway router.
  • Pinged the first hop (as reported by traceroute) behind my gateway router. Losses start there.
  • The router itself has a diagnose panel, which displays 0 for the router and the switching centre.
  • There is no cyclic pattern in the bursts of packet loss. At least for my untrained eyes.
  • The connection is unusable in this state. I couldn't even solve the captcha for minutes, because of connection errors.

Matt's TraceRoute Screenshot

Wireshark Capture at Cloudshark