IP Address Overlapping Error

  • Hi Guys,

    I have recently upgraded to the new version of PFsense 2.3.1 AMD64 and have encountered a strange problem.

    I have 1 x Inside Interface  (192.168.100.x) and two Outside interfaces x.x.x.x on a 28bit subnet - giving me around 13 usable IP's.  However, when I try and set the IP of the second of these addresses, I get the following  "IPv4 address xxxx/xx is being used by or overlaps with: OUTSIDE_1 (xxxx/xx)"

    These are separate public addresses.

    Anyone came across this?  Is it a bug?



  • LAYER 8 Global Moderator

    well without some details of the 2 networks your trying to set, have to assume the reason for the error is they overlap ;)

  • Thanks for your reply.

    without giving too much details:

    Outside_1  is  x.x.x.156/28
    Outside_2  is  x.x.x.157/28

    They worked fine in the previous version.  This is not a new install it was an upgraded of an existing config

    There is no overlap, just not sure why it thinks there is.

    Anyone any ideas?

  • Obviously there is an overlap.

    Both x.x.x.156/28 and x.x.x.157/28 would go from x.x.x.144 to x.x.x.159.

    You may want to try using an IP calculator such as:

    Jorge M. Oliveira

  • LAYER 8 Global Moderator

    Yeah as Jorge stated, that would be a overlap…

    What is the 3rd octet?

  • Sorry guys maybe I'm being a little thick here.

    But I have a range of public ip's 144-159 (defined by the 28bit subnet mask)  I want to set two IP's in this range as external interfaces.  With previous version of PfSense I would state Outside_1 = x.x.x.155/28  and Outside_2 = x.x.x.156/28.  These are two separate hosts in this range, so why can't set an interface to each host.  It work before, unless I'm missing something obvious.


  • LAYER 8 Global Moderator

    Why would you put 2 interfaces in the same network?  Are you saying your internet connection speed is higher than 1 interface speed?

    If you want to use multiple IPs in the same network as wan IPs, just put them as VIP on your interface.

    How is this physically connected to your isp.. if you want more than 1 physical connection create a lagg.  Then put your IP(s) on the lagg.

  • I have two external interfaces to split the services I have on the inside N/W.  Some services are very similar and require specific ports, so it's a way of using a particular port.


  • Hi Guys,

    I restored the XML file onto the system again, and now it seems happy enough.  Not sure what happened.

    Thanks for the replies.


  • I have the same issue in 2.3.2.

    I use console to setup interface, It works, But webgui can't.

  • LAYER 8 Netgate

    You want to use one interface with an interface address and Virtual IPs, not two interfaces.

  • I was in the same situation and I solved by using Virtual IP.

    Set the first interface normally,
    and set the second interface's static IP with Link-Local IP ( first,
    and add a Virtual IP for that interface with the IP and subnet you actually want for the interface.

    Then I was able two use two interfaces on one subnet.

    I know it would be better to use rather a LAGG interface, not two interfaces in this case.
    But the router my server is linked does not support LACP or link aggregation, so I had to settle with this solution for now.
    It had 10Gb links going outside so the actual bottleneck on my server was the link between the server and the router.
    And for load balancing, I'm currently using PBR to split its traffic by protocols and sources.
    But still this is a temporary solution and I'm still finding a way into LAGG config.

  • Netgate Administrator

    Please don't open threads from 3 years ago. If you are hitting something like this on the current version it's unlikely to be the same thing as something this old. It would have affected many people and would have been fixed since then. Please start your own thread to report an issue agains 2.4.4p2.

    This is fact does not look like a bug though. You cannot have two interfaces in the same subnet, that is invalid. You can obviously have multiple IPs but they should be added as virtual IPs on the initial interface.


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