Strange problem with forwarded 443 to exchange server and Spectrum Modem

  • At my work, we have an interesting problem.  NOTE: this problem exists with either our pfSense router OR our old SonicWall.

    We run Exchange 2016 / Outlook Anywhere.  When we forward port 443 through to the server, within about 10 minutes or so, our Spectrum-provided Arris modem starts rebooting.  It goes down for 5-10 minutes, comes back up for about 5-10 minutes,  and repeats this behavior until we block port 443 through to the Exchange server.

    If I turn off the web service on the server, the problem stops, OR if I disable the forwarding rule it stops.

    Of course, leaving this turned off makes my mobile users rather testy since they can't get their email.

    There is something going on related to how the exchange server is somehow responding to traffic being sent to it, thus causing the modem to reboot.

    We have been fighting this issue for some time.  We got some relief for a few weeks by getting Spectrum to replace our modem with a different unit that doesn't reboot, but has horrible ping times (3s!) until this past Sunday when that modem died and the tech replaced it with another Arris unit.  Then the rebooting started again.

    I don't know where to look from here.  I get the notion that this is malicious attack for some reason because of this last data point:

    The rebooting behavior starts around 8-10am and stops at 5-7 pm.  System stays up rock solid all night long.  We have rebuilt the Exchange server TWICE in case there was a problem.  We replaced our SonicWall with pfSense.  The problem persists.

    Please give me some idea where to look next to track this down.  The boss is getting pretty upset.

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