No internet from opnsense in bridge mode

Started by SoScuba, August 14, 2025, 05:14:12 PM

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Hello, I'm a total beginner with opnsense so apologies if I did something stupid.

I'm trying to configure opnsense as a transparent filtering bridge (because I'd rather keep using my FritzBox as a router for both Wifi and wired clients).

My opnsense device has 3 ports:

  • port 0 (WAN) is connected to my modem/router
  • port 1 (LAN) is connected to my main switch
  • port 2 (MGMT) is a management port

The bridge is composed of the WAN and LAN interfaces.

My current configuration seems to be mostly working except that opnsense itself has no internet access, which means I can't get updates or install plugins.

I have tried to follow this guide: https://homenetworkguy.com/how-to/configure-opnsense-transparent-filtering-bridge/

But I have an issue at step 7.1, if I try to add a gateway for the management interface then it fails saying that the IP already exists (which is true: my router is already defined as a gateway on the WAN interface).

What am I supposed to do here? If I put the gateway on the MGMT interface instead of the WAN interface then I have no internet access from the LAN.

If I connect to the console I can see that there is no default route:

Internet:
Destination        Gateway            Flags         Netif Expire
127.0.0.1          link#5             UH              lo0
<LAN subnet>    link#3             U              igc2
<MGMT IP>      link#5             UHS             lo0

If I add a route manually using

route add default <router IP>
then opnsense has internet access but that only works until the next reboot and it obviously isn't clean...

Nevermind it seems that putting the gateway on the MGMT interface was indeed correct but that a reboot was required to make it work.