Re: Bizarre packet loss
On Thu, 22 Oct 2020 22:07:18 -0400 Gregory Seidman wrote: > If I ping the Debian server from OpenWRT, the wireless device, or the > wired device I get 25%-30% packet loss *unless* I am pinging an > external IP from the Debian server at the same time, at which point > the packet loss goes below 1%. I have no explanation for this. Bizarre, indeed. The first thing I try is to cycle power on all three routers simultaneously. Leave them off for at least 20 seconds. Sometimes they just lose their marbles. Failing that, mtr (package mtr-tiny for the command line version) is an excellent diagnostic tool for this sort of thing. It will tell you where a problem lies much better than ping will. E.g.: mtr -r -i 3 -c 10 debian.org -- Does anybody read signatures any more? https://charlescurley.com https://charlescurley.com/blog/
Re: Bizarre packet loss
On 2020-10-22 19:07, Gregory Seidman wrote: First off, here's the network architecture: ISP (untrusted) router (NAT) | OpenWRT (trusted) router (NAT) ... wireless device | Cisco (unmanaged) switch---+ | | Netgear (unmanaged) switchwired device | Debian server If I ping the Debian server from OpenWRT, the wireless device, or the wired device I get 25%-30% packet loss *unless* I am pinging an external IP from the Debian server at the same time, at which point the packet loss goes below 1%. I have no explanation for this. But wait, it's even weirder than that. Pinging from one wireless device to another wireless device *also* shows significant (~20%) packet loss unless the Debian server is pinging an external IP. Note that pinging an external IP from a wired or wireless device doesn't seem to have any impact. I suspect that something bad is happening at the Ethernet layer that I'm just not seeing, but I don't know where it's coming from or what I'm looking for. I've used tcpdump from the places where I can (OpenWRT, Debian server, wired and wireless devices) and looked at it in Wireshark, but nothing jumps out at me. There is a pretty strong chance that this isn't coming from the Debian server at all, but a ping from it has some magical effect on the network. I've been fighting this for days and I'm just at a loss. I'd very much appreciate any advice or options to try. Thanks, --Gregory I would verify that all of the Ethernet cables are good. Fix or discard any that have issues: https://www.idealind.com/shop/62-200.html https://www.idealind.com/shop/30-696.html https://www.idealind.com/shop/85-396.html David
Bizarre packet loss
First off, here's the network architecture: ISP (untrusted) router (NAT) | OpenWRT (trusted) router (NAT) ... wireless device | Cisco (unmanaged) switch---+ | | Netgear (unmanaged) switchwired device | Debian server If I ping the Debian server from OpenWRT, the wireless device, or the wired device I get 25%-30% packet loss *unless* I am pinging an external IP from the Debian server at the same time, at which point the packet loss goes below 1%. I have no explanation for this. But wait, it's even weirder than that. Pinging from one wireless device to another wireless device *also* shows significant (~20%) packet loss unless the Debian server is pinging an external IP. Note that pinging an external IP from a wired or wireless device doesn't seem to have any impact. I suspect that something bad is happening at the Ethernet layer that I'm just not seeing, but I don't know where it's coming from or what I'm looking for. I've used tcpdump from the places where I can (OpenWRT, Debian server, wired and wireless devices) and looked at it in Wireshark, but nothing jumps out at me. There is a pretty strong chance that this isn't coming from the Debian server at all, but a ping from it has some magical effect on the network. I've been fighting this for days and I'm just at a loss. I'd very much appreciate any advice or options to try. Thanks, --Gregory
