MetalLB in L2

Kubernetes architecture requires a LoadBalancer.

MetalLB can be deployed as a LoadBalancer in L2 mode, which is good for bare metal homelab style environments.

Example Deployment

deployment/controller   1 replica
daemonset/speaker       7 pods   

Theory

Controller

• Watches for LoadBalancer request
• Picks a free IP out of the pool
• Assigns it to the Service as its EXTERNAL-IP

Speaker

• bound to hostNetwork
• Runs stateless hash
• First on the list advertise the MetalLB IPs

L2 Operation

Is the service running?

kubectl get l2advertisements -n metallb-system

What services are consuming an IP?

kubectl get svc -A --field-selector spec.type=LoadBalancer

How the L2 leader election works

• Stateless

1. Creates a list of all speakers could announce the IP.
2. Sorts the list with a specific hash.
3. First speaker on the list announces the IP (responds to ARP).

References

metallb.io/