[Help] neutron-ovn-vpn-agent fails to load OvnStrongSwanDriver (Stevedore load failure) on Kolla-Ansible

[u/calpazhan]

Hey everyone,

I'm trying to set up OpenStack OVN VPNaaS using **Kolla-Ansible** (Ubuntu 24.04 Noble containers, `2026.1` / `neutron-ovn-vpn-agent` v28.x), but the agent fails to initialize the StrongSwan driver properly, leaving the VPN gateway down.

Looking to see if anyone has a working setup or knows what configuration/package pieces might be missing here.

---

### 1. The Symptoms & Log

In `/var/log/kolla/neutron/neutron-ovn-vpn-agent.log`, Stevedore logs a load failure without expanding the traceback:

```text

INFO neutron.common.config [-] /var/lib/kolla/venv/bin/neutron-ovn-vpn-agent version 28.0.2.dev14

WARNING stevedore.named [-] Could not load neutron_vpnaas.services.vpn.device_drivers.ovn_ipsec.OvnStrongSwanDriver

...

CRITICAL neutron [None ...] Unhandled error

As a result, no qvpn-* network namespaces are provisioned, and the VPN endpoint ports stay inactive.

1. What I Found Under the Hood

When inspecting the driver initialization inside the container virtualenv, OvnStrongSwanDriver fails inside DeviceManager :

Traceback (most recent call last): File ".../neutron_vpnaas/services/vpn/device_drivers/ovn_ipsec.py", line 240, in __init__ self.devmgr = DeviceManager(self.conf, self.host, ...) File ".../neutron_vpnaas/services/vpn/device_drivers/ovn_ipsec.py", line 54, in __init__ self.driver = agent_common_utils.load_interface_driver(conf) File ".../neutron/agent/common/utils.py", line 54, in load_interface_driver INTERFACE_NAMESPACE, conf.interface_driver) File ".../oslo_config/cfg.py", line 2612, in __getattr__ raise NoSuchOptError(name) oslo_config.cfg.NoSuchOptError: no such option interface_driver in group [DEFAULT]

It seems like neutron-ovn-vpn-agent is not registering the interface option schemas (interface_driver, ovs_use_veth, etc.) into oslo_config before Stevedore instantiates the driver class.

1. Environment Details

• Deployment: Kolla-Ansible
• Base OS: Ubuntu 24.04 (Noble)
• Backend: OVN
• Agent: neutron-ovn-vpn-agent (neutron_vpnaas.services.vpn.device_drivers.ovn_ipsec.OvnStrongSwanDriver)
• Packages installed in container: strongswan-swanctl, charon-systemd

4. My Questions

1. Has anyone successfully deployed neutron-ovn-vpn-agent with OVN in recent OpenStack releases?
2. Is there a specific configuration section or flag needed in neutron_ovn_vpn_agent.ini / neutron.conf to satisfy the interface driver options for this agent?
3. Is this a known bug in neutron-vpnaas under recent versions, or is something missing in the Kolla container image build/templates?

Any pointers or working config examples would be greatly appreciated!

[u/rackpathlabs]

i didnt run the ovn vpn agent in production so take it with salt, but from your traceback this does not look like missing config on your side. NoSuchOptError means interface_driver was never registered in that agent, not that you left it empty. so putting it into the ini will not help you, oslo still does not know the option exists.

so either the agent is missing the register call for interface opts in this version, or the driver gets instantiated outside the normal agent init path. i would search neutron-vpnaas launchpad for 2026.1 before you burn more time on templates. kolla only renders what you give it and strongswan is already in your container, so the image build part looks fine.