How does pfSense detect a network failure?



  • I have set up a pfSense at a very small hotel with 2 WAN and 2 LAN.

    The WAN part is provided as two ADSL lines with Thomson modems. I am just wondering how pfSense can detect if one of these modems drops their internet connection? It is fully possible that the connection from pfSense to the modem is working perfect, while there is no connection to the internet.

    The modems connect to the internet via PPPoE and give a private IP address to pfSense. I think it should be possible to route the official IP address through to pfSense, but has not had any time to investigate this yet.



  • You have to change the monitor ip under system->gateways to something else than the modem lan ip.
    It will make detection work as you expect after.



  • I guess you meant System>Routing>Gateways :-)

    Found it after a little bit of searching through the menus there. Thanks! I set it to monitor the DNS address of the ISP. Is that an OK address, or should I aim for something else? Does it matter if both WAN's monitor the same address? In my head, it should not matter, but better safe than sorry!



  • You dns isp server is ok depending on your link.
    If it is dynamic and ppp type it makes sense otherwise not so much.

    For using the same ip in both WAN the culprit is mostly having both of them fail if that ip fails.
    Other than that it is ok.



  • Yes, the DSL connections use PPPoE. BTW - just realised the last message could be understood as a sarcastic message. That was NOT the intention! I am truly grateful for the help here!

    Both connections use the same gateway, so I guess I could also use that as a test, the logic being - if a modem fails the gateway will not be reached. If the gateway fails, both lines will fail no matter what. I will ask if it is possible to connect through a different gateway for one of the modems. It is in the middle of a city. But I don't know if there are options and how willing the ISP is to help.


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