I am looking to setup CARP following this guide across two pfSense firewalls.

I have setup CARP before on a WAN link with a big IP space, so allocating a distinct WAN IP per each device (as shown in the guide) was palatable.

Now, I am trying to do the same, but only one WAN IP is available per link.

Is there a way to use only one WAN IP?

Edit: What if you have the following configuration? (would this work?)

  • WAN1: WAN IP, local IP
  • WAN2: WAN IP, local IP
  • pf1: On interface WAN1, local IP; on WAN 2, local IP;
  • pf2: On interface WAN1, local IP; on WAN 2, local IP;
  • On both pf1 and pf2, monitor IP set to the ISP-appropriate value
  • VIP on,

No, carp requires three WAN IPs.

  • 2
    Just to clear it up, this is not true since version 2.2. It is now possible to use CARP with as little as just one WAN IP, setting the interfaces IP as private ones and your WAN IP as CARP IP.
    – tstark81
    Oct 4 '16 at 13:15

It does not, it depends on your Setup. I have a working solution with 1 IP. The Slave just uses the Master as a gateway.

  • Would you care to share how this is done? Jul 15 '15 at 21:22
  • 1
    On the Internet-interface i have a separate network which is being used to negotiate the VIP, the IP itself is configured as CARP IP. Other than that i just gave each Firewall a seperate gateway with lower priority which points to the other firewall so that both firewall can route to the internet. Jul 20 '15 at 14:53
  • Alessandro, how do you manage to have the lowpri routes pointing to the other firewall? do you have the static route sync turned off? Oct 14 '15 at 20:04
  • Hi Florian - the other Firewall is just the secondary default gateway for the non-master firewall. And the first gateway is the providers gateway which is not reachable when there is no CARP IP assigned (=Slave) Oct 20 '15 at 7:35
  • Thank you that's simple and elegant. I did not come up with that idea, as much as I tried ;) Oct 23 '15 at 17:55

CARP is like VRRP, HSRP and most other routing redundancy protocols, you must have 3 static IPs in the same subnet.

That may change at some point in the future, but it's true for the time being.

  • Any VRRP / HSRP setup I've seen so far has not used IPs from the attached subnet for the cluster interfaces themselves. Dec 1 '15 at 3:42

this topic has been requested as a feature in the pfsense bugtracker https://redmine.pfsense.org/issues/3859 and also issue 4597

and in this post https://forum.pfsense.org/index.php?topic=87546.msg495163#msg495163

it seems possible but you have to work around the webGUI

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