Virtlet networking

One interface

Virtlet, as other CRI implementations, uses CNI (Container Network Interface). When only one interface is used then no additional configuration is required. As you saw in the previous chapter it just works.

Multiple interfaces

For multiple interfaces Virtlet uses CNI-Genie. When running demo.sh script you have set MULTI_CNI=1 which tells kubeadm-dind-cluster to install CNI-Genie and two network providers: flannel and calico.

Check that all is already installed:

kubectl -n kube-system get pod

You should see genie, flannel and calico-related pods in the output.

See Virtlet docs for more details about multiple interfaces support.

demo.sh script configured CNI-Genie to create two network interfaces for each newly created pod. That includes docker pods and Virtlet pods.

Check the ubuntu-vm to see that it has already configured two interfaces. Attach to the VM (log in as testuser/testuser):

kubectl attach -it ubuntu-vm-with-testuser

and list addresses on interfaces:

ip address

See how to specify which networks to use:

cat examples/ubuntu-multi-cni.yaml

See cni: "calico,flannel" annotation. It tells CNI-Genie which networks to use. If no cni annotation is specified then default plugin will be used. In demo.sh script default is set also to "calico,flannel":

docker exec kube-node-1 cat /etc/cni/net.d/00-genie.conf