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Weird 10Gbe networking problems (lemmy.world)

submitted 11 months ago* (last edited 11 months ago) by tmjaea@lemmy.world to c/selfhosted@lemmy.world

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Hi,

I've got a network setup consisting of 3 proxmox servers of which two have a 10Gbe interface. All interfaces are RJ45 copper ports.

So far I've got two qnap switches with 2 10Gbe and 5 2.5Gbe portss. They are connected to each other via one of the 10Gbe ports, and one of the servers on the other one.

This setup is working flawlessly, iperf measurements show 9.4gbit/s in both directions.

Recently I tried to increase my network for future expansion and bought a trendnet switch with 5 10Gbe ports.

Weird problems occurred and as they were also described in some amazon reviews I returned the switch and bought another one, this time a 4port 10Gbe switch from ubiquity.

Again there are problems. This time one direction seems to be at 10gbit/s as expected while the other direction (between the same two servers) is limited to 1gbit/s. The connection to the third server shows the same problem (one direction 2.5gbit/s and the other one limited to 1gbit/s).

All wires are connected correctly and as there is no problem on the qnap switches I do believe that there is no hardware problem on the cable/NIC side.

However I'm not sure if this is this just bad luck or some deep network problem I don't understand.

Maybe someone has an idea?

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[–] bigredgiraffe@lemmy.world 0 points 11 months ago* (last edited 11 months ago)

So then it doesn’t work across the ubiquity switch just to double check? If so, you will need to enable jumbo frames on that for sure and it is not enabled by default and that could also explain the throughput as it is having to fragment then defragment the frames to cross the switch or iperf is using MSS to determine that it can only send 1500 byte frames, your slower speed is about line rate for 1500 byte frames no matter the speed of the actual link.

ETA: you can verify this by pinging with a large size and setting the “do not fragment” flag, so something like ‘ping -s 2000 -M do ip.addr ’ on Linux, windows uses different flags.