OpenStack Networking Debug -- SDN Troubleshooting Operations

Networking debug is the most hands-on troubleshooting domain in cloud operations. Virtual networks add multiple abstraction layers between user intent and physical packets -- an instance's traffic passes through a tap device, a Linux bridge or OVS port, integration bridge flows, tunnel encapsulation, and physical NIC before reaching the wire. When connectivity breaks, the operator must trace through every layer to find where packets stop flowing.

The debugging mental model: Start at the instance and trace outward. The packet path for a tenant instance is: instance vNIC -> tap device -> qbr bridge (if OVS with iptables) -> OVS br-int -> tunnel or VLAN tag -> OVS br-ex (for external traffic) -> physical NIC. For OVN, the path simplifies: instance vNIC -> OVS br-int (with OVN flows) -> tunnel or physical port. Every hop is inspectable. Every hop can be the failure point.

This skill is the primary reference for the CRAFT-network agent when diagnosing connectivity issues during Phase E operations.

Deploy

Debug Tooling Setup

Verify all diagnostic tools are available before beginning any debug session.

OVS diagnostic commands (available inside openvswitch_vswitchd container):