Diagram

Here's a text-based network diagram for your k3s cluster across two VMs on separate physical machines:

Network Diagram

+-----------------------------------------------------------------------------------------+
|                                      Home Lab Network                                   |
|                                (LAN/WAN, e.g., 192.168.1.0/24)                         |
|                                                                                         |
|  +-----------------------------+          +-----------------------------+              |
|  |  Physical Machine 1         |          |  Physical Machine 2         |              |
|  | +-------------------------+ |          | +-------------------------+ |              |
|  | |     VM 1 (Master Node)   | |          | |     VM 2 (Worker Node)  | |              |
|  | |  - IP: 192.168.1.10      | |          | |  - IP: 192.168.1.11     | |              |
|  | |  - k3s Control Plane     | |          | |  - k3s Agent            | |              |
|  | |    - kube-apiserver      | |          | |    - kubelet            | |              |
|  | |    - etcd (embedded)     | |          | |    - containerd         | |              |
|  | |  - Longhorn Manager      | |          | |  - Longhorn Replica     | |              |
|  | |  - MetalLB Controller   | |          | |  - MetalLB Speaker      | |              |
|  | +------------|-------------+ |          | +------------|-------------+ |              |
|  +--------------|---------------+          +---------------|--------------+              |
|                   |                                        |                             |
|                   |                  Router/Gateway        |                             |
|                   |                (e.g., 192.168.1.1)     |                             |
|                   +----------------------------------------+                             |
+-----------------------------------------------------------------------------------------+

Key Components & Flow

Physical Machines:
- Each runs a VM with static IPs (192.168.1.10 for master, 192.168.1.11 for worker).
- Connected via the same LAN/WAN subnet for inter-VM communication.
k3s Control Plane (Master):
- Hosts the Kubernetes API server (kube-apiserver), scheduler, and embedded etcd (for storage).
- Manages cluster state and worker node coordination.
- Critical ports: 6443 (API), 8472 (Flannel VXLAN), 10250 (kubelet).
k3s Worker Node:
- Runs pods/deployments via containerd runtime.
- Connects to the master via K3S_URL (API server on 6443).
Networking:
- Flannel: Provides pod-to-pod networking (VXLAN over 8472).
- MetalLB: Assigns external IPs to services (Layer 2 mode, e.g., 192.168.1.100-192.168.1.150).
Storage:
- Longhorn: Replicates persistent volumes across both nodes (syncs data between longhorn-manager and longhorn-replica).
External Access:
- Ingress traffic (e.g., HTTP/80, HTTPS/443) routed via MetalLB to Traefik/Nginx Ingress Controller.

Traffic Flow Example

+----------------+       +----------------+       +----------------+       +----------------+
| External User  | ----> | MetalLB VIP    | ----> | Ingress (Traefik) | ----> | App Pod (Worker) |
+----------------+       +----------------+       +----------------+       +----------------+
                                  ↑
                                  | Service IP: 192.168.1.100

Critical Connections

Master ↔ Worker:
- Kubernetes API (6443): Worker polls master for instructions.
- Flannel VXLAN (8472): Pod-to-pod cross-node networking.
- Longhorn Sync: Replicates storage volumes between nodes.
External ↔ Cluster:
- MetalLB assigns external IPs to LoadBalancer-type services.
- Ingress controllers (Traefik/Nginx) route HTTP(S) traffic to pods.

Security Notes

Firewall rules should allow bidirectional traffic on ports 6443, 8472, and 10250.
Use SSH key authentication for VM access.
Restrict MetalLB IP pool to unused addresses in your subnet.

Tools to Visualize

For an actual diagram, use tools like:

Draw.io (free, browser-based)
Lucidchart
Excalidraw (hand-drawn style)

Let me know if you'd like a step-by-step config for any specific component!