This is an optional step since it is possible to reconfigure an existing bridge on the host. However, using separate bridge for the data plane traffic helps to isolate that traffic from other virtual devices.
To create a new bridge using the generic procedure:
iface ens3f0 inet manual
auto vmbr1
iface vmbr1 inet manual
bridge-ports ens3f0
bridge-stp off
bridge-fd 0