Dual wans on the same subnet

  • I have two fios connections that are on the same subnet. My current firewall ( fortigate), will not allow this since the gateway is the same.

    fios1 = gateway =
    fios2 = gateway -

    (These are obviously not their numbers, and they are not behind routers)

    I have been told that pfsense would not have an issue with this. We have tried for 4 weeks to get verizon to change one of the lines to a different network, but it looks like it is not possible. We also have a cable modem that would be for failover. I know I could put them on routers and then nat one or both, but I am looking to not do that.


  • Hi,

    I had the same problem with two modems from the same ISP. Some times I would get a unique gateway on both modems but sometimes I would get the same gateway if one modem flapped. It really screwed things up and load balancing collapsed. It got worse when I went over to a Vlan configuration the same MAC address was presented to the ISP out or both modems even if I tried to manually set one under one of the WAN  interfaces.
    To cure all my problems I just plopped an old access point in the path of one of the modems with everything turned off. So I'm using its MAC address to go to the ISP and its 10.x.x.x address as a gate way to my router.


  • So you cannot use two WAN's that are using the same subnet for loadbalancing or as i want it, for port forwarding?

  • If both WANs are using the same gateway IP, you need an intermediate NAT device. The balancing or policy routing is done by gateway IP.

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