Network speed on isolated vmbr

[Dnezar]

Hi. I can't really find anywhere what determines the network speed between 2 nodes on a virtual bridge that has no gateway or physical NICs attached to them. I created a bridge and attached it to host and a VM and tested the speed using dd command write to dev>null and wasn't able to reach more than 800 MB/s. I had thought the speed would be higher. My CPU is an E5-2697A V4 and when doing the write test I can see it go up to 20% usage.
What is the limiting factor here?

 

[_gabriel]

I assume you meant "between two VM" :
speed between two VM over a Linux Bridge is bounded to the host CPU.
iperf is the tool to do the speedtest.
btw, 800 MB/s = 6,4 Gb/s