Neighbours

ovs-appctl

Also rstp/show, stp/show, RSTP status, port role, port state, Open vSwitch spanning tree

Asks a running Open vSwitch for internal state the database does not show — here, its Rapid Spanning Tree view.

ovs-appctl sends a command to a live Open vSwitch daemon and prints what it answers. ovs-appctl rstp/show br0 is the one to know for spanning tree: it prints the bridge's RSTP view — the root it sees, its own bridge ID, and each port with its role (Root, Designated, Alternate) and state (Discarding, Learning, Forwarding). The root bridge says This bridge is the root. (stp/show is the same for classic 802.1D.) The matching per-port values are also in the database — ovs-vsctl get port NAME rstp_status — for scripting.

ovs-appctl command usage

ovs-appctl rstp/show [BRIDGE]
ovs-appctl stp/show [BRIDGE]

Options

rstp/show br0: br0's Rapid Spanning Tree roles and states
stp/show br0: the same for classic 802.1D

ovs-appctl examples

ovs-appctl rstp/show br0: Prints the root, the bridge's own ID, and each port's role and state.
ovs-vsctl get port floor1 rstp_status:rstp_port_role: Reads one port's RSTP role from the database, for a script.

Reading the output

$ ovs-appctl rstp/show br0
---- br0 ----
Root ID:
  stp-priority    4096
  This bridge is the root
Interface  Role       State      Cost
---------- ---------- ---------- ----
floor1     Designated Forwarding 200
printer    Designated Forwarding 200

This bridge is the root: it has the lowest bridge ID.
An Alternate port shown Discarding is the backup that breaks the loop.

Pitfalls

The roles update as the tree converges: read twice a second apart and compare if you need a settled view.
ovs-appctl needs the daemon running; it talks to it over a unix socket, not the network.

Run it on real machines