I found a way to create a virtual network interface (like veth in linux):

ifconfig feth0 create
ifconfig feth1 create
ifconfig feth0 peer feth1

Then you can add it to the existed bridge:

ifconfig bridge1 addm feth0

All command must run with root (sudo).

Source: https://apple.stackexchange.com/questions/337715/fake-ethernet-interfaces-feth-if-fake-anyone-ever-seen-this