Open Stack

We are configuring Neutron's vpnaas extension and although the guide 
seems to be quite short, it looks like that there are some dependencies 
that we are not aware of since we are receiving this error when we start 
the neutron server:

WARNING stevedore.named [req-dca2e9a8-1799-45c7-9380-f247510af7e5 - - - 
- -] Could not load 
neutron_vpnaas.services.vpn.device_drivers.libreswan_ipsec.LibreSwanDriver

We have followed this guide 
https://docs.openstack.org/neutron/latest/admin/vpnaas-scenario.html and 
before that we have also installed the below packages from the repos:

openstack-neutron-vpnaas-17.0.0-2.el8.noarch

libreswan-3.32-7.el8_3.x86_64

our config files are the below:

l3_agent.ini

[DEFAULT]
interface_driver = linuxbridge
debug = true
[AGENT]
extensions = vpnaas
[vpnagent]
vpn_device_driver = 
neutron_vpnaas.services.vpn.device_drivers.libreswan_ipsec.LibreSwanDriver

neutron_vpnaas.conf

[service_providers]
service_provider = 
VPN:openswan:neutron_vpnaas.services.vpn.service_drivers.ipsec.IPsecVPNDriver:default

vpn_agent.ini is empty since the guide documents the changes in the 
l3_agent.ini file

in neutron.conf we have also added the below:

service_plugins = router,vpnaas

At this point, my main question would be, is VPNaaS supported with linux 
bridge or just with OpenvSwitch?

Thanks in advance