Troubleshooting VM Launch Issues with OVN Networks in oVirt Clusters

Adding a new node to an existing oVirt Cluster should be a seamless process, but sometimes you hit a snag. That’s exactly what happened to me recently when I realized that only virtual machines (VMs) without an OVN network were launching. For those who might not be familiar, OVN (Open Virtual Network) is a system that provides network virtualization to containers and VMs, and it’s a critical component for managing external VM networks within oVirt’s infrastructure.

Identifying the Culprits

After some digging, I pinpointed the issue to two specific problems:

1. OVN services were not properly initiated on the new oVirt Node Host.
2. A necessary VDSM (Virtual Desktop and Server Manager) configuration command had not been executed.

Implementing the Fixes

Here’s how I resolved these issues:

For the OVN Services:

The OVN services need to be enabled and started on the oVirt Node Host. This ensures that the necessary services for network virtualization are running and available. To do this, I used the following commands:

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systemctl enable openvswitch systemctl enable ovn-controller systemctl start openvswitch systemctl start ovn-controller

For the VDSM Configuration:

The VDSM tool comes with a utility to configure OVN. This step is crucial as it links your oVirt Node with the OVN provider. The command looks like this:

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vdsm-tool ovn-config <oVirt Engine IP> <oVirt Node IP>

Replace <oVirt Engine IP> with the IP address of your oVirt Engine, and <oVirt Node IP> with the IP address of your oVirt Node.

Additional Resources

For those who are setting up or troubleshooting their oVirt and OVN setup, I found the following resource to be incredibly helpful:

• oVirt Software Defined Networking – The OVN Network Provider

This blog post from the oVirt team provides an in-depth look at how OVN functions within the oVirt ecosystem.

Conclusion

If you’re encountering similar issues with your VMs and OVN networks in oVirt, I hope the steps I’ve outlined can help you as they did for me. Remember, the key to managing a smooth oVirt environment often lies in the details of service management and configuration. If you have any questions or additional insights, feel free to drop a comment below.

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