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Weird 10Gbe networking problems

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?

kelvie ,

Have you tried playing with the flow control settings on your ubiquiti switch? I was having problems streaming video games until I toggled that setting (forget if it was on or off, though).

tmjaea OP ,

As I am not sure if I should keep it return it I hesitated to do anything else than using it as a dumb switch.

bigredgiraffe ,

Can you draw a picture of how you have all 3 switches connected with all of the wires? I am suspicious that you are creating a switching loop or spanning tree isn’t picking the optimal link on accident so I’m curious.

vettnerk ,

I was thinking the same thing. Spanning tree is love. Spanning tree is life…when deployed correctly.

Alternatively I’m thinking noise, as I’ve seen that in 10gig connections a few times, which is why I prefer LC fiber where possible.

bigredgiraffe ,

Oh yeah for sure, every time I’m like “it can’t be spanning tree” it is spanning tree. Do you mean copper vs fiber? LC connectors can carry a variety of speeds but generally yeah I try to use fiber or DAC cables which are shielded wherever I can.

tmjaea OP ,

It’s just two switches.

Server 1 — 10Gbe — ubiquity switch — 10Gbe — qnap switch — 10Gbe — server 2.

bigredgiraffe , (edited )

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.

tmjaea OP ,

Yes,

It does not work. Additionally, the ubiquity switch does not sync with 10gbit/s to one of the qnap switches (I tested with different cables and ports, but the led on the qnap stays orange, indicating connection speed lower than 10gbit/s)

As I’m maybe returning the switch due to the problems I hesitate to register it to access settings. Jumbo frames settings could actually be the solution. But with the problem mentioned in the first paragraph I’m not sure. A 300€ device should just work IMHO…

Thanks for the suggestion with ping, I will test it.

perslue ,

I’ll ask some basics:

Is the ubiquity switch the flex-xg? Make sure you’re using the 10G ports as the poe port is only 1G.

I’m assuming all the ethernet cables are rated for 10G?

Are any of the switches or NICs manually configured to negotiate at a lower transmit rate?

That’s all I’ve got, good luck.

tmjaea OP ,

Thanks for your input. All criteria you mentioned are met.

If I build the same connection with the second qnap switch instead of the ubiquity it is working flawlessly.

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