i have two ubunutu vm started using virt-manager say vm1 and vm2. Both has one interface has one network interface ( vnet0 and vnet1 respectively ) and they are bridged using virbr0 ( using brctl command ). i excuted command netperf -H "vm2 ip address" from vm1 ubuntu machine. i got result = 164. I wrote a usespace program - which creates two tap devices ( tap1 and tap2) and will read from tap1 and write to tap2 ( and vice versa ) using epoll system call. i removed vibr0 brdige. i bridged ( using brctl ) tap1 and vnet0 together and tap2 and vnet1 together. i repeated above netperf test. I am getting same 164. In the first test, i avoided 2 userspace copies and 2 read system call and 2 write system call. why performance is same in both case ? any hint is really appreciated ? Thanks, Ratheesh