motivation
I got some new sfp modules today, and i wanted to validate them... I was feeling lazy to drag two machines together to plug in the sfp modules for a point to point link (plus many machines don't even have sfp slots), I was feeling lazy to daisy chain two switches together to use the sfp modules.....
I do have iperf3 testing already setup on a stable host server pair in my network... so
Setup two vlans A, B. These vlans have no dhcp, no routes, nothing - Attach a interface to each vlan, assign as static ip address on the same subnet, run iperf3 in server mode. The test comes from how you bridge the vlans: A switch with vlan A on port A, and vlan B on port B, now if you plug in SFP.A and SFP.B and bridge with a cable... iperf3 can connect.
This extends your in place network path from interface A to interface B by forcing it to go over SW.PortA->SFP.A->Test Cable->SFP.B->->SW.PortB
Host interface A
│
│ VLAN A
▼
switch.portA ── Test SFP.A
│
│ test-cable
│
switch.portB ── Test SFP.B
▲
│ VLAN B
│
Host interface B
Run iperf3 in a loop, and now you can swap modules/cables and get the full benefit of a point to point cable test without having to move any machines around. This will even work with a single machine for testing, with a interface on A and B (different namespaces), you just have to double your iperf results mentally.
I realize this is fairly niche, and probably obvious to many people, but I just stumbled upon it today and thought it was pretty neat.
FWIW my SFP modules ran at 9.6gbps, so I'm happy with them!
This feels illegal
The man is trying to get you not to use VLANs!
Can i interest you in a plastic baggie of dubiously sourced sfp modules?