ISP Modem Mode Reverted - Question.



  • Hello there,

    Earlier today I discovered that my ISP modem/router, which I had set to "Modem Mode" as to use my new pfsense box to handle my small home network/firewall needs, had somehow reset itself back to its original state thus disabling Modem Mode.  I can't be clear how long it has been like this.

    What prompted me to check the ISP device was a vast quantity of the following entry in the pfsense logs:  Block ULA networks from WAN block fc00::/7 (12000).  (The rule info:  @58(1200) block drop in log quick on re1 inet from 10.0.0.0/8 to any label "Block private networks from WAN block 10/8")  I'd also began to discover the normal entries that pfBlocker was making to the logs (in respect of GeoIP blocks) were getting less and less.  To the point that they stopped happening.

    Some of the threads on the forum suggested unchecking "Block private networks and loopback addresses" to clear this log entry, others said it was IPV6 related and not to be too concerned.  Unchecking "Block private networks and loopback addresses" did indeed appear to completely stop that entry from showing up.

    After putting the ISP modem back into Modem Mode and re-checking "Block private networks and loopback addresses" the message returned but only twice every 7-10 minutes.  The normal pfBlocker entries all came streaming back as normal too resolving that particular issue for me.

    2 questions hoping someone could help me with:  1)  Is it likely that with this ISP router being "turned on" as opposed to modem mode being active and pfsense running through it, will this have caused any problems with the pfsense box in respect of configuration?  Do I need to do anything now pfsense is working with modem mode on again?  Anything I should be concerned about?

    2)  Regarding Block ULA networks from WAN block fc00::/7 (12000) - I'm still not entirely clear with my set up whether I should simply uncheck "Block private networks and loopback addresses" permenantly which seems to resolve the issue.  Or should I just ignore the log entry as it doesn't seem to be causing any problems.

    Any help would be much appreciated.

    Thank you.



    1. your ISP probably updated the firmware on their kit and reset it back their defaults.  Some do that.

    2. You know what is causing the situation, it’s up to you.  I’d ignore them, but others might disagree.



  • @motific:

    1. your ISP probably updated the firmware on their kit and reset it back their defaults.  Some do that.

    2. You know what is causing the situation, it’s up to you.  I’d ignore them, but others might disagree.

    Thank you motific - Much appreciate the response.


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