CARP with only one available WAN ip address



  • We have a /30 netblock to manage the link between our ISP's router and us, with a larger netblock routable via our systems.  So of the two usable ip addresses on the 30 network, the lower address is used by their router and is our gateway to the Net, while the higher address is used by our kit and is the gateway to our larger DMZ netblock.

    Now, I'd like to use a pair of pfsense boxes to link all this together, but I can't create the VIP because the web interface will not allow me to create a VIP where there is no matching subnet already configured on an interface.

    Is there a practical way for me to get around that restriction, or am I just going to have to put in something else to manage the initial link?

    Using the latest stable version, btw.


  • Rebel Alliance Developer Netgate

    There is no currently supported/working way to do CARP on WAN with a single IP address. You need at least three: One for each box, and the shared CARP VIP.

    This may change in the future if carpdev ever makes its way in. From what I understand that lets the routers have IPs in a separate subnet from the shared IP. But for now, with only a /30 on WAN, something will have to talk to that.

    In doing so, however, you lose the high availability that CARP gains you and you're back to a single point of failure.


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