Here is information about the network:

  • I have 2 WAN connections to the same ISP which they provided 2 modems for and configured them to be in bridge mode.
  • My MDF router (pfSense) connects both of them through two different physical interfaces.
  • One interface is configured for DHCP and the other is static, with a static IP and gateway provided by my ISP.
  • The WANs are setup to be load balancing on the router (which works as expected).
  • From the pfSense web GUI I can see the interfaces get their public IP address & gateway addresses.
  • I have a LAN network of a typical, but I can still access the web interface for these modems at

Since their web interfaces are both accessible through, although they are connect to different interfaces on the same router, can they interfere with each other and kick each other offline?

I am having connectivity issues, latency, and packet loss when they are connected at the same time, but do not seem to have as much of an issue when I have one at a time connected.

  • 2
    You really don't want ambiguous addressing on your network and should consider renumbering one of the transfer networks.
    – Zac67
    Jan 13, 2023 at 21:39

2 Answers 2


There's only a problem when they're on the same wire ("broadcast domain") -- but it won't stop either modem from working. And it's only a problem for you as you won't know which one will respond. Which ever one your system accepts as the answer to the ARP request will be the one you're talking to. As they're on separate interfaces, which one you talk to is up to routing -- which ever link the load balancing selects will be the modem you see, and that could change unpredictably.


You have 2 different issues, most likely but neither is well explained in the question. The services described appear to be consumer cable internet services (modems as described are generally for DOCSIS cable internet) and DHCP configured internet service is generally consumer/home use service which I believe is off topic here.

The first issue is the packet loss while both internet services are connected. You'll need to get a lot deeper into that issue and clarify whether the issue happens with either service when only that one is connected. You seem unsure whether that is the case for sure, possibly that you do have packet loss with only one connection or the other as well. Start by nailing that down. Once you verify both internet services are reliable on their own, then you can figure out why they don't work when you try to have PFSense use them as failover.

The second issue is simply reliable access to the local management interface of the modem. The modem 'watches' for traffic passing through it destined for and replies with its management interface for local diagnostic display. That should never interfere with other traffic. That diagnostic interface is simply to access things like signal strength data, etc. about the cable connection. That configuration of the IP address for the management interface is set by the cable service provider via a config download to the modem when it boots up and you cannot change it and they probably won't either. In any case, you probably don't need to care about it unless you routinely want to check the signal strength of your cable connection on both services for some reason. You can probably just ignore that IP address for most of your life.

The main problem is probably a misconfiguration of PFSense in the failover/load balancing of the 2 internet services, possibly compounded by a problem with the reliability of one or both connections.

  • 1
    While I agree, DSL and DOCSIS are "consumer level", they're sold to and used by a great many businesses. I've run various enterprises off DSL and cable many times -- it's cheap and quickly available. (I'd also add xPON, but you can get decent bandwidth/latency these days.)
    – Ricky
    Jan 16, 2023 at 19:54
  • Definitely true that DSL and DOCSIS can be used for businesses and are sold that way, the original question seemed to indicate that at least one of the connections was probably sold under a 'home user' type account based on the use of DHCP (just my assumption really though). It's probably not too relevant to the actual issue though. I think it is basically a PFSense configuration problem or possibly hardware issue. Jan 20, 2023 at 20:53
  • Business accounts use DHCP. The addresses change so infrequently, it's rarely necessary to pay for the privilege of statics. I've run dns, smtp, and web on dynamic addresses. VPNs are little messy on DHCP, but I only have to clean that up every few years.
    – Ricky
    Jan 21, 2023 at 1:58

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