Disable WAN Interface on CARP Backup

10-wancarp

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

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

@stevencoutts Do tell, how did you manage to configure this functionality directly within OpnSense?

The main thing I was missing was CARP on the VLAN interface of my WAN port. I had tried CARP on the physical interface, but it had to be on the VLAN. It works as expected now.

That sounds like a solution that only works for PPPoE connections. I believe that the "Disconnect dialup interfaces" functionality has been in there for a while now. This script is trying to solve the failover situation for any interface connection, including things like fiber, cellular bridge, or cable modem connections.

For anyone landing here later: I made a working fork for my setup, tested on OPNsense 26.1.6.

Warning: it is vibe-coded / AI-assisted, so please review it carefully before using it in production.

You must adapt the CARP trigger subsystem, interface key, and gateway name placeholders to your own setup.

In my environment, it correctly keeps the DHCP WAN inactive on BACKUP and active on MASTER.

Fork: Link