> For the complete documentation index, see [llms.txt](https://documentation.opencrvs.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://documentation.opencrvs.org/v2.0/technical/guides/installation/advanced-topics/ubuntu-firewall-configuration.md).

# Ubuntu Firewall configuration

### Overview

The firewall follows a default-deny approach:

* All inbound traffic is denied by default.
* Only ports required for cluster operation are opened.
* Firewall rules are managed automatically by Ansible.
* Existing OpenCRVS-managed rules are removed and recreated during each deployment to ensure configuration consistency.

### Unrestricted access

* `SSH`: All nodes allow inbound SSH connections on TCP port 22.
* `HTTP/HTTPS`: Control plane node (master) allows inbound traffic on 80 and 443 ports. These ports are used by Traefik to expose OpenCRVS services.

### Kubernetes API

Control plane node allows access to the Kubernetes API server on TCP port 6443 from:

* All Kubernetes cluster nodes
* Additional CIDR ranges specified through the `kubernetes_api_allowed_cidrs` configuration option

This allows cluster components to communicate with the API server while enabling operators to restrict administrative access to trusted networks.

### Internal Cluster Communication

OpenCRVS automatically discovers all Kubernetes node IP addresses and creates firewall rules allowing communication between cluster members only.

The master node's IP address comes from `KUBE_API_HOST`, and the worker addresses come from `KUBE_WORKER_NODES`. These must be the addresses the nodes use to reach each other. If the master node has both a public and a private network interface, set `KUBE_API_HOST` to the private IP address. Otherwise the firewall blocks traffic from the master to the worker nodes, and commands such as `kubectl logs` fail with `dial tcp <worker IP>:10250: i/o timeout`.

The following ports are opened between cluster nodes:

| Port  | Protocol | Purpose                         |
| ----- | -------- | ------------------------------- |
| 6443  | TCP      | Kubernetes API Server           |
| 10250 | TCP      | Kubelet API                     |
| 10251 | TCP      | kube-scheduler                  |
| 10252 | TCP      | kube-controller-manager         |
| 179   | TCP/UDP  | Calico BGP                      |
| 4789  | UDP      | Calico VXLAN overlay networking |
| 7946  | TCP/UDP  | Cluster networking components   |
| 8472  | UDP      | VXLAN overlay networking        |

{% hint style="info" %}
`etcd` communication ports (2379 and 2380) are not exposed publicly and are intended only for control plane communication within the cluster.

To support Calico networking, inbound traffic is allowed on the following interfaces:

* `cali+`
* `vxlan.calico`
  {% endhint %}

### Configuration options

| GitHub variable/secret    | Ansible variable          | Description                                                                                                                                       |
| ------------------------- | ------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------- |
| KUBE\_API\_HOST           | kube\_api\_host           | Kubernetes master node IP address. On a master node with several network interfaces, use the IP address from shared with the worker nodes subnet. |
| KUBE\_API\_ALLOWED\_CIDRS | kube\_api\_allowed\_cidrs | Subnets approved to access Kubernetes API server (master). Comma-separated list (e/g: `10.0.0.0/16,192.168.0.0/24`)                               |
| KUBE\_WORKER\_NODES       | n/a                       | Kubernetes worker nodes. Comma-separated list (e/g: `10.0.0.2,10.0.0.3,10.0.0.4`)                                                                 |


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://documentation.opencrvs.org/v2.0/technical/guides/installation/advanced-topics/ubuntu-firewall-configuration.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.