Dual Wan with Same Wan Subnet and Same DNS

  • Trying to setup my dual wan connection and have a few questions to ask.

    My current setup is dual wan and 1 gigabit lan.

    I was interested in setting up Dual Wan via this article: http://doc.pfsense.org/index.php/MultiWanVersion1.2

    But I hit an issue. My modems are both part of the same subnet (actually only 1 number apart. One is xxx.xxx.xxx.231 the other is xxx.xxx.xxx.232). Thus they have the same DNS servers.

    I wanted to setup 3 pools like the article but am stumped at what I should use for the Ping ip for each. I can't use DNS because it will just ping it from the other WAN correct? Should I use the other modems ip as the ping?

    Please Help.

    Also I wanted to see if I could setup Traffic Shaping on this setup. I heard that it may not be available for dual wans yet. Is there an update on that?

    Thanks in advance.

  • Thraffic shapins is not possible with dual WAN.
    Having both WAN's in the same subnet is not possible also.

    You will need a cheap 20$ router in front of on of the two interfaces to create an additional subnet between the pfSense and the actual WAN.

  • Oh well… no traffic shaping, no biggie.

    But the Dual wan is needed. If I put a router before each modem, how would that help? Even If i have them on different subnets the ping would still be the internet.

    If I do that, then what ip do I use to test the line? I can't use the cheap routers ip because that will always resolve fine. If I use the DNS then won't it just use the other modem to route the ping, thus killing the whole point of it?

    Perhaps I am too n00bish or just confused. My setup is as follows.

    Modem 1 (xxx.xxx.xxx.231) -> Wan 1 Port
    Modem 2 (xxx.xxx.xxx.232) -> Wan 2 Port

    Both modem 1 & 2 are on the same subnet and have the same DNS.

    Gigabit Lan ( -> Lan 1 port

  • I have a similar situation. I am running a multi wan setup all on the same network.
    all but one wan are setup through cheap routers.

    I don't really worry about the monitor ip's because if the wan goes down for me they all go down. Your situation may differ.

    I just set the monitor ip to the interface's gateway. wan -> wan's gateway, opt1 -> opt1's gateway etc.

    hope this helps!

  • Take a look at the routing table.
    There is an entry for each subnet that is directly reachable.
    The routing table is processed from top to down.
    If there are 2 entries for the same subnet (for both interfaces one entry) then only one entry will have an effect. (because it's sequentially processed and not concurrent).
    Now if you have one of the both interfaces in a different subnet and a cheap router in front the routing table will look different –> pfSense is able to distinguish the two subnets.
    From the outside it wont make a differenece but from the inside it's something else.

    If you want to know more you should take a look at the basics of how routing works. (wikipedia is a great source).

  • Got it working with a Load Balancing Pool. Just setup both Cable modems to run DHCP and host on their own subnet. Works like a charm.

    Thanks for all the feedback.

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