Using this repo, you can leverage nested namespaces to deploy an OVN cluster where outer namespaces represent a compute node -- aka OVN chassis. Inside each of these emulated chassis, we are then able to create inner namespaces to emulate something comparable to ports of a VM in a compute node.

For more details, take a look at this talk from the 2019 OVScon: Deploying multi chassis OVN using docker in docker by Numan Siddique, Red Hat: Slides Video

Step 1: Build the container images

By default, Docker is used (we can switch to Podman later):

OVN_SRC_PATH=<path_t_ovn_src_folder> OVS_SRC_PATH=<path_to_ovs_src_folder> sudo ./ovn_cluster.sh build

This will create 2 docker images

• ovn/cinc: base image that gives us the nesting capability
• ovn/ovn-multi-node: built on top of cinc where ovs+ovn is compiled and installed

Step 2: Start openvswitch in your host

In order to interconnect the containers that emulate the chassis, we need an underlay network. This step is what provides that.

sudo /usr/share/openvswitch/scripts/ovs-ctl --system-id=testovn start

Step 3: Start the ovn-fake-multinode

sudo ./ovn_cluster.sh start

Step 4: Stop the ovn-fake-multinode and tweak cluster as needed

sudo ./ovn_cluster.sh stop

# look for start-container and configure-ovn functions in
vi ./ovn_cluster.sh

# Go back to step 3 and have fun!

A port called ovnfake-ext is created in the fake underlay network as part of ovn_cluster.sh start. You can use that as an easy way of getting inside the cluster (via NAT in OVN). Look for ip netns add ovnfake-ext in ovn_cluster.sh. An example for doing that is shown here:

sudo ip netns exec ovnfake-ext bash
ip a
ip route
ping -i 1 -c 1 -w 1 172.16.0.110 >/dev/null && \
   echo 'happy happy, joy joy' || echo sad panda
exit

To deploy a VM that automatically performs the steps above as part of it's provisioning, consider using Vagrantfile located in this repo.

git clone https://github.com/numansiddique/ovn-fake-multinode.git && \
cd ovn-fake-multinode && vagrant up && vagrant ssh