Intro

In my previous [article]({{< ref "post/12-opnsense-virtualization-highly-available" >}}) I set up a PoC to validate building a cluster of two OPNsense VMs in Proxmox VE to make the firewall highly available.

Now I'm preparing to make that real in my homelab, this post documents my real OPNsense cluster configuration, from fresh installs to HA, DNS, DHCP, VPN and reverse proxy.

Context

Before diving into the OPNsense configuration, a little bit of context to understand the choices I made.

In my Proxmox VE cluster, I've created 2 VMs and installed OPNsense. The goal is to replace my single physical box by this cluster. Each VM have 7 NICs for the following networks:

• vmbr0: Mgmt
• vlan20: WAN
• vlan13: User
• vlan37: IoT
• vlan44: pfSync
• vlan55: DMZ
• vlan66: Lab

Initially I was thinking of just restoring my current configuration on the VM freshly installed. But then I realized that I didn't really documented how I put the pieces together the first time. This is the perfect moment to put things right.

⚠️ I can only have a single WAN IP, shared between the nodes, served by the DHCP of my ISP box. For this reason I won't have a VIP for the WAN and I have to find a solution to share this single IP.

Hopefully in the next post, if this project lands on my production network, I will also cover the VM creation on Proxmox and how I'm preparing this migration from my physical OPNsense box to this highly available cluster in VMs. Let's dive in!

System

General

I start with the basics, in System > Settings > General:

• Hostname: cerbere-head1 (cerbere-head2 for the second one).
• Domain: mgmt.vezpi.com.
• Time zone: Europe/Paris.
• Language: English.
• Theme: opnsense-dark.
• Prefer IPv4 over IPv6: tick the box to prefer IPv4.

Users

Then, in System > Access > Users, I create a new user rather than using root, add it to the admins group, and remove root from that group.

Administration

In System > Settings > Administration, I change several things:

• Web GUI
  • TCP port: from 443 to 4443, to free port 443 for the reverse proxy coming next.
  • HTTP Redirect: Disabled, to free port 80 for the reverse proxy
  • Alternate Hostnames: cerbere.vezpi.com which will be the URL to reach the firewall by the reverse proxy.
  • Access log: Enabled.
• Secure Shell
  • Secure Shell Server: Enabled.
  • Root Login: Disabled.
  • Authentication Method: Permit password login (no root login).
  • Listen Interfaces: Mgmt
• Authentication
  • Sudo: No password.

Once I click Save, I follow the link given to reach the WebGUI on port 4443.

Updates

Time for updates, in System > Firmware > Status, I check for firmware updates and apply them (requires reboot).

QEMU Guest Agent

Once updated and rebooted, I go to System > Firmware > Plugins, I tick the box to show community plugins. I install the QEMU Guest Agent, os-qemu-guest-agent, to allow communication between the VM and the Proxmox host.

This requires a shutdown. On Proxmox, I enable the QEMU Guest Agent in the VM options: Proxmox VM options with QEMU Guest Agent enabled

Finally I restart the VM. Once started, from the Proxmox WebGUI, I can see the IPs of the VM which confirms the guest agent is working.

Interfaces

On both firewalls, I assign the remaining NICs to new interfaces adding a description. The VMs have 7 interfaces, I carefully compare MAC addresses to avoid mixing interfaces:

In the end, the interfaces configuration looks like this:

I don't configure Virtual IPs yet, I'll manage that once high availability has been setup.

High Availability

Firewall Rule for pfSync

From here we can associate both instances to create a cluster. The last thing I need to do, is to allow the communication on the pfSync interface. By default, no communication is allowed on the new interfaces.

From Firewall > Rules > pfSync, I create a new rule on each firewall:

Configure HA

OPNsense HA uses pfSync for firewall state synchronization (real-time) and XMLRPC Sync to push config and services from master → backup (one-way).

The HA is setup in System > High Availability > Settings

Master

• General Settings
  • Synchronize all states via: pfSync
  • Synchronize Peer IP: 192.168.44.2, the backup node IP
• Configuration Synchronization Settings (XMLRPC Sync)
  • Synchronize Config: 192.168.44.2
  • Remote System Username: <username>
  • Remote System Password: <password>
• Services to synchronize (XMLRPC Sync)
  • Services: Select All

Backup (cerbere-head2):

• General Settings
  • Synchronize all states via: pfSync
  • Synchronize Peer IP: 192.168.44.1, the master node IP

⚠️ Do not fill the XMLRPC Sync fields on the backup node, only to be filled on the master.

HA Status

In the section System > High Availability > Status, I can verify if the synchronization is working. On this page I can replicate any or all services from my master to my backup node:

Virtual IPs

Now that HA is configured, I can give my networks a virtual IP shared across my nodes. In Interfaces > Virtual IPs > Settings, I create one VIP for each of my networks using CARP (Common Address Redundancy Protocol). The target is to reuse the IP addresses used by my current OPNsense instance, but as it is still routing my network, I use different IPs for the configuration phase:

ℹ️ OPNsense allows CARP by default, no special firewall rule required

CARP Failover Script

In my setup, I only have a single WAN IP address which is served by the DHCP of my ISP box. OPNsense does not provide natively a way to handle this scenario. To manage it, I implement the same trick I used in the [PoC]({{< ref "post/12-opnsense-virtualization-highly-available" >}}).

Copy MAC Address

I copy the MAC of the net1 interface of cerbere-head1 and paste it to the same interface for cerbere-head2. Doing so, the DHCP lease for the WAN IP address can be shared among the nodes.

⚠️ Warning: Having two machines on the network with the same MAC can cause ARP conflicts and break connectivity. Only one VM should keep its interface active.

CARP Event Script

Under the hood, in OPNsense, a CARP event triggers some scripts (when the master dies). These are located in /usr/local/etc/rc.syshook.d/carp/.

To manage WAN interface on each node, I implement this PHP script 10-wan on both nodes, using SSH (do not forget to make it executable). Depending on their role (master or backup), this will enable or disable their WAN interface:

#!/usr/local/bin/php
<?php

require_once("config.inc");
require_once("interfaces.inc");
require_once("util.inc");
require_once("system.inc");

$subsystem = !empty($argv[1]) ? $argv[1] : '';
$type = !empty($argv[2]) ? $argv[2] : '';

if ($type != 'MASTER' && $type != 'BACKUP') {
    log_error("Carp '$type' event unknown from source '{$subsystem}'");
    exit(1);
}

if (!strstr($subsystem, '@')) {
    log_error("Carp '$type' event triggered from wrong source '{$subsystem}'");
    exit(1);
}

$ifkey = 'wan';

if ($type === "MASTER") {
    log_error("enable interface '$ifkey' due CARP event '$type'");
    $config['interfaces'][$ifkey]['enable'] = '1';
    write_config("enable interface '$ifkey' due CARP event '$type'", false);
    interface_configure(false, $ifkey, false, false);
} else {
    log_error("disable interface '$ifkey' due CARP event '$type'");
    unset($config['interfaces'][$ifkey]['enable']);
    write_config("disable interface '$ifkey' due CARP event '$type'", false);
    interface_configure(false, $ifkey, false, false);
}

In Interfaces > Virtual IPs > Status, I can force a CARP event by entering into Persistent maintenance mode. Triggering this allow me to test this script, which disable the WAN interface on the master while enabling it on the backup.

Firewall

Let's configure the core feature of OPNsense, the firewall. I don't want to go too crazy with the rules. I only need to configure the master, thanks to the replication.

Interface Groups

Basically I have 2 kinds of networks, those which I trust, and those which I don't. From this standpoint, I will create two zones.

Globally, my untrusted networks only have access to DNS and the internet. Trusted networks can reach other VLANs.

To begin, in Firewall > Groups, I create 2 zones to regroup my interfaces:

• Trusted: Mgmt, User
• Untrusted: IoT, DMZ, Lab

Network Aliases

Next, in Firewall > Aliases, I create an alias InternalNetworks to regroup all my internal networks:

Firewall Rules

For all my networks, I want to allow DNS queries on the local DNS. In Firewall > Rules > Floating, let's create the first rule:

Next I want to allow connections towards the internet. At the same place I create a second rule:

Finally, I want to allow anything from my trusted networks. In Firewall > Rules > Trusted, I create the rule:

Great, with these 3 rules, I cover the basics. The remaining rules would be to allow specific equipment to reach out to something else. For example my home assistant instance want to connect to my TV, both are on different VLAN, hence I need a rule to allow it:

DHCP

For the DHCP, I choose Dnsmasq. In my current installation I use ISC DHCPv4, but as it is now deprecated, I prefer to replace it. Dnsmasq will also act as DNS, but only for my local zones.

Dnsmasq doesn't sync leases. To avoid conflicts, both nodes serve DHCP but with staggered reply delay and different ranges. The master covers the main pool, the backup a small fallback pool

Dnsmasq General Configuration

In Services > Dnsmasq DNS & DHCP > General, I configure the master firewall as follow:

• Default
  • Enable: Yes
  • Interface: Mgmt, User, IoT, DMZ and Lab
• DNS
  • Listen port: 53053
• DNS Query Forwarding
  • Do not forward to system defined DNS servers: Enabled
• DHCP
  • DHCP FQDN: Enabled
  • DHCP local domain: Enabled
  • DHCP authoritative: Enabled
  • DHCP reply delay: 0
  • DHCP register firewall rules: Enabled
  • Disable HA sync: Enabled

On the backup node, I configure it the same, the only difference will be the DHCP reply delay which I set to 10. This gives the master time to answer DHCP requests before the backup responds.

DHCP Ranges

Next I configure the DHCP ranges. Both firewalls will have different ranges, the backup node will have smaller ones (only 10 leases should be enough). On the master, they are configured as follow:

DHCP Options

Then I set some DHCP options for each domain: the router, the dns-server and the domain-name. I'm pointing the IP addresses to the interface's VIP:

Hosts

Finally in in the Hosts tab, I define static DHCP mappings but also static IP not managed by the DHCP, to have them registered in the DNS:

DNS

For the DNS, I use Unbound. It is a validating, recursive, caching DNS resolver built into OPNsense, which can:

• Resolve queries from the root servers.
• Cache results for faster responses.
• Check domain authenticity with DNSSEC.
• Block domains based on a blacklist.
• Add custom records.

Unbound is the recursive resolver, for local zones I forward queries to Dnsmasq.

Unbound General Settings

Let's configure it, in Services > Unbound DNS > General:

DNS Blocklist

Then I configure the blocklist in Services > Unbound DNS > Blocklist. I enable it and select the [hagezi] Multi PRO mini list. Initially I was using AdGuard Home, but I want to give this blocklist feature a chance.

To maintain the service up to date, in System > Settings > Cron, I add my first job that runs every night at 2AM to Update Unbound DNSBLs.

Query Forwarding

Finally I configure query forwarding for my local domains to Dnsmasq. In Services > Unbound DNS > Query Forwarding, I add each of my local domains with their reverse lookup (PTR record):

VPN

When I'm not home, I still want to be able to reach my services and enjoy my DNS ad blocker. For that I'm setting up a VPN, with WireGuard. It's fast, secure and easy to set up.

WireGuard Instance Setup

In VPN > WireGuard > Instances, I create a new one:

• Enabled: Yes
• Name: Homelan
• Public/Private keys: Key-pair generated
• Listen port: 61337
• Tunnel address: 10.13.37.1/24
• Depend on (CARP): on lan (vhid 1)

Once configured, I enable WireGuard and apply the configuration.

Peer Setup

Next in the Peer generator tab, I fulfill the empty fields for my first device:

• Endpoint: vezpi.com
• Name: S25Ultra
• DNS Servers: 10.13.37.1

Before clicking Store and generate next, from my device, I configure the peer by capturing the QR code. Finally I can save that peer and start over for new ones.

Create VPN Interface

This step is not required, but ease the configuration management for firewall rules. On both firewall, in Interfaces > Assignments, I assign the wg0 (WireGuard - Homelan) interface and name it VPN.

Then in Interfaces > VPN, I enable this interface.

Finally, in Firewall > Groups, I add this interface in the Trusted group.

Firewall Rule

To allow connections from outside, I need to create a firewall rule on the WAN interface:

Reverse Proxy

The next feature I need is a reverse proxy, to redirect incoming HTTPS requests to reach my services, such as this blog. For that I use Caddy. It will listen on port 80/443, that's why I moved the WebGUI off these ports at the beginning.

This service is not installed by default, I need to add a plugin. On both firewalls, In System > Firmware > Plugins, I tick the box to show community plugins and install os-caddy.

Caddy General Settings

I refresh the page and, on the master, in Services > Caddy > General Settings:

• Enable Caddy: Yes
• Enable Layer4 Proxy: Yes
• ACME: <email address>
• Auto HTTPS: On (default)

There are two types of redirections, the Reverse Proxy and the Layer4 Proxy. The first one is for HTTPS only, where Caddy will manage the SSL.

Reverse Proxy

In Services > Caddy > Reverse Proxy, I define the services directly managed by Caddy.

These services should not be exposed to everyone. In the Access tab, I create a list, called Internal, of allowed networks, including my LAN and VPN networks.

Then in the Domains tab, I add my domains. For example, this is here I define cerbere.vezpi.com, my URL to reach my OPNsense WebGUI:

• Enable: Yes
• Frontend
  • Protocol: https://
  • Domain: cerbere.vezpi.com
  • Port: leave empty
  • Certificate: Auto HTTPS
  • HTTP-01 Challenge Redirection: 192.168.44.2, for high availability setup
  • Description: OPNsense
• Access
  • Access List: Internal
  • HTTP Access Log: Enabled

Finally in the Handlers tab, I define to which upstream these domains are forwarded to. For cerbere.vezpi.com I define this:

• Enabled: Yes
• Frontend
  • Domain: https://cerbere.vezpi.com
  • Subdomain: None
• Handler
  • Path: any
• Access
  • Access List: None
• Directive
  • Directive: reverse_proxy
• Upstream
  • Protocol: https://
  • Upstream Domain: 127.0.0.1
  • Upstream Port: 4443
  • TLS Insecure Skip Verify: Enabled
  • Description: OPNSense

Layer4 Proxy

Most of my services are behind another reverse proxy on my network, Traefik. To let it manage normally its domains, I forward them using Layer4 Routes. It prevents Caddy to terminate SSL, the HTTPS stream is left intact.

In Services > Caddy > Layer4 Proxy, I create 3 routes.

The first one is for internet exposed services, like this blog or my Gitea instance:

• Enabled: Yes
• Sequence: 1
• Layer 4
  • Routing Type: listener_wrappers
• Layer 7
  • Matchers: TLS (SNI Client Hello)
  • Domain: blog.vezpi.com git.vezpi.com
  • Terminate SSL: No
• Upstream
  • Upstream Domain: 192.168.66.50
  • Upstream Port: 443
  • Proxy Protocol: v2, if your upstream supports it
  • Description: External Traefik HTTPS dockerVM

The second one is for internal only services. It is configured pretty much the same but using an access list:

• Sequence: 2
• Access
  • Remote IP: 192.168.13.0/24 192.168.88.0/24 10.13.37.0/24

The third one is for Traefik HTTP challenges for Let's Encrypt:

• Sequence: 3
• Layer 7
  • Matchers: HTTP (Host Header)
  • Domain: blog.vezpi.com git.vezpi.com etc.
• Upstream:
  • Upstream Port: 80
  • Proxy Protocol: Off (default)

Firewall Rules

Finally, I need to allow connection of these ports on the firewall, I create one rule for HTTPS (and another for HTTP):

mDNS Repeater

The last service I want to setup in OPNsense is a mDNS repeater. This is useful for some devices to announce themselves on the network, when not on the same VLAN, such as my printer or my Chromecast. The mDNS repeater get the message from an interface to forward it to another one.

This service is also not installed by default. On both firewalls, In System > Firmware > Plugins, I tick the box to show community plugins and install os-mdns-repeater.

Then in Services > mDNS Repeater, the configuration is pretty straight forward:

• Enable: Yes
• Enable CARP Failover: Yes
• Listen Interfaces: IoT, User

Service Synchronization

The final step is to synchronize all the services between the master and the backup node in the cluster. First in System > High Availability > Status, I click the button to Synchronize and reconfigure all.

Then I want to make sure that future changes are synchronized if I omit to replicate them myself. In System > Settings > Cron, I add a new job that runs every night to HA update and reconfigure backup.

Conclusion

🚀 My OPNsense cluster is now configured and ready to go live!

I hope this OPNsense full configuration for my own network, help you with your own setup.

The next phase is to plan the migration from my current OPNsense box to these two highly available firewalls. This new infrastructure would secure my future operations on the firewall, while removing this SPOF (Single Point Of Failure) of my network.

See you next time to tell how this operation went!