ComCast cable WAN does not recover well after an outage.

  • My primary WAN is a ComCast cable modem.  I use AT&T UVerse as a failover.  That seems to work fine when the cable goes out, which, I'm sad to say, is fairly frequent.  Unfortunately, the cable does not recover well after an outage.  I pretty much have to reboot the pfSense router to get it straightened out.  My router is a NetGate m1n1wall, and I'm running pfSense 2.2.6 on it.  I may consider swapping to let UVerse be my primary, but the cable is faster and appears to have the lower latency.

    Any thoughts how to get it to recover without needing a reboot?


  • Does it have any IP on WAN after the outage? Probably the most common cause of that symptom is the cable modem handing out a private IP DHCP lease when it loses upstream connectivity, which requires a release and renew, or waiting for that lease to timeout, once it's back up.

    With an ALIX, there are some modems that don't play nicely with those vr NICs. In that case, putting a small switch between the modem and WAN port generally will resolve.

  • Yes, there is usually an IP that shows up during the recovery process, but the status bounces between "Pending" and "Online."  It sounds as if your diagnosis may be spot on.  I'll dig up a switch and give your suggestion a try.


  • And it's a public IP? If so and you see it bouncing up and down, then yeah I'd try putting a switch in between, that sounds like the exact symptoms of when you run into that problem.

  • Sadly, that does not seem to help.  I dug up an older 100Mbps switch from a closet and stuck it between the cable modem and the pfSense router.  The first thing I noticed after resetting things was that when I powered down the cable modem, the router didn't appear to even notice.  Eventually, it did go into a "Pending" mode, but it still thought it had a valid IP address and I never got a failover to the UVerse WAN.  Turning the cable modem back on resulting in no recovery at all.  I still needed to reset the modem and the router.

    As far as I can tell, the IP address that I'm given by ComCast is a public one.  It is not an RFC1918 address.


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