Skip to content

network – Tagged VLAN traffic goes only one way between mac and Linux

  • by

I used to have a Mac Mini 2018 with 10Gpbs ethernet connected to my 10Gbps switch. I had a tagged vlan to access my NAS. It worked very well last time I checked. I don’t remember when I actually checked it last time, but at least everything – time machine, shared mounts, etc – seemed to be working fine) until I replaced it with a Mac Studio in april.

Then I realized something weird: traffic between Mac Studio and other macs on my network – 10Gbps or not – flows very well on tagged vlans. However, traffic between my Mac Studio and my NAS (and then between my Mac Studio and other Linux machines) goes only one way – Mac -> Linux, when using a tagged vlan. I get no traffic from the linux machines back to the mac. Linux <–> Linux works well, Mac <–> Mac works well.

I thought initially this was a Mac Studio issue. So I tested with a MacBook Pro M1. Same problem. I thought, oh well, this might be an M1 issue. I borrowed a MacBook Pro 2018, and again, same issue.

I used iperf3 for testing. I changed the switches – my network has mostly Ubiquiti switches, but I also have a small Mikrotik, and I tested with it. I even tested traffic between a mac and a Linux VM on ESXi running on a Mac Mini 2014. Still the same issue: traffic goes only one way between macOS and non-macOS. I also tried different Linux distros (Fedora, Ubuntu, TrueNAS Scale).

I am inclined to believe this is a Monterey issue, but my previous Mac Mini did have Monterey (although it was still one of the first versions).

The only thing I haven’t tested is traffic to a linux machine that is not on a VM. All my tests were between a mac and a Linux hosted on a VM under ESXi. But still, traffic between Linux on different hosts/machines/esxi-nodes worked fine.

Traffic that goes on untagged vlan flows normally.

Any clue on how to debug this properly to get the culprit?

EDIT: just to clarify, I don’t believe it is an MTU issue. I had jumbo frames enabled all the way (the Mac Studio had absolutely the same configuration as my previous Mac Mini, which had its MTU adjusted to 9000). And, as said, it does work between two macs and to Linux machines. I also tried with the standard MTU (1500), adjusting it all along the way, and same behavior.

EDIT #2: I manage to test traffic between the Mac and a Linux (Fedora) on bare metal, again, on tagged vlan. It worked. So maybe ESXi is the problem.

Leave a Reply

Your email address will not be published. Required fields are marked *