Step-by-Step Guide: Setting Up a K3s Cluster with MetalLB and Multiple

Setting up a lightweight Kubernetes cluster with K3s and integrating it with MetalLB for load balancing is a powerful way to manage your containerized applications. In this guide, we’ll walk through setting up a K3s cluster with MetalLB and multiple agent nodes. We’ll configure the master node to listen on 0.0.0.0 and disable the default Service Load Balancer.

Prerequisites

Servers:
- kali Linux(192.168.1.210)(mater-node) MASTER_NODE_PUBLIC_IP is name for local setup
- Ubuntu2((192.168.1.207)(k8s-vm-worker-1)
- MetalLB IP Pool range (192.168.1.10-192.168.1.50)
Access:
- SSH access to all nodes.
Network:
- All nodes should be able to communicate with each other over a private network.
Tools Installed:

curl, iptables, and kubectl (optional for management).

Step 1: Install K3s on the Master Node

Update the Master Node:
```
 sudo apt update
```

Install K3s:

 curl -sfL https://get.k3s.io | sh -s - server \ 
     --disable servicelb \
     --node-external-ip 192.168.1.210 \ #<MASTER_NODE_PUBLIC_IP>
     --node-ip 192.168.1.210 \ #<MASTER_NODE_PRIVATE_IP>
     --bind-address 0.0.0.0

Replace:

<MASTER_NODE_PUBLIC_IP> with the public IP of the master node (if applicable).
<MASTER_NODE_PRIVATE_IP> with the private IP of the master node.

Confirm K3s Installation:
```
 sudo kubectl get nodes
```

Step 2: Retrieve the Join Token

On the master node, retrieve the join token that agent nodes will use to join the cluster:

sudo cat /var/lib/rancher/k3s/server/node-token

Copy the token for later use.

Step 3: Install K3s on Agent Nodes

Update Each Agent Node:
```
 sudo apt update
```
Install K3s Agents:

Run the following command on each agent node:
```
 curl -sfL https://get.k3s.io | K3S_URL=https://<MASTER_NODE_IP>:6443 \ 
     K3S_TOKEN=<TOKEN> sh -s - agent \
     --node-external-ip <AGENT_NODE_PUBLIC_IP> \
     --node-ip <AGENT_NODE_PRIVATE_IP>
```
Replace:
- <MASTER_NODE_IP> with the master node’s private IP.
- <TOKEN> with the token copied earlier.
- <AGENT_NODE_PUBLIC_IP> and <AGENT_NODE_PRIVATE_IP> with the respective IPs of the agent node.
Verify Nodes Are Added:

On the master node, check the status of the cluster:
```
 sudo kubectl get nodes
```
All nodes (master and agents) should be listed.

Step 4: Install MetalLB

Deploy the MetalLB Manifest:

Apply the official MetalLB manifest:

 kubectl apply -f https://raw.githubusercontent.com/metallb/metallb/main/config/manifests/metallb-native.yaml

Create a ConfigMap for MetalLB:

Determine a range of IPs on your network to use for load balancing. For example, 192.168.1.10-192.168.1.50.

Create a ConfigMap for MetalLB:

 cat <<EOF | kubectl apply -f -
 apiVersion: metallb.io/v1beta1
 kind: IPAddressPool
 metadata:
   name: pool
   namespace: metallb-system
 spec:
   addresses:
   - 192.168.1.10-192.168.1.50 # example: 192.168.1.10-192.168.1.50
 ---
 apiVersion: metallb.io/v1beta1
 kind: L2Advertisement
 metadata:
   name: l2-advertisement
   namespace: metallb-system
 spec:
   ipAddressPools:
   - pool

 EOF

Verify MetalLB Installation:
```
 kubectl get pods -n metallb-system
```
Ensure all MetalLB pods are running.

Step 5: Test Load Balancing

Deploy a Sample Application:

—load-balancer-ip can define from matallb ip pool range

 kubectl create deployment nginx --image=nginx
 kubectl expose pod my-nginx --port=80 --type=LoadBalancer --load-balancer-ip=192.168.1.11

Check the Load Balancer IP:
```
 kubectl get services
```
You should see an external IP assigned from the MetalLB range.
Access the Application:

Open a browser or use curl to access the external IP:
```
 curl http://192.168.1.11
```

notes: 192.168.1.1 is not able to ping.

Best Practices

Regularly update K3s and MetalLB to the latest versions.
Monitor node health using tools like kubectl top or a monitoring solution.
Use a firewall to secure access to cluster nodes.

How to Set Up a K3s Cluster with MetalLB and Multiple Agent Nodes

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