Flapping WAN with axe interface

[Adam Hunt]

I just replaced my old WRT54GS running DD-WRT at home with a proper pfSense
firewall. The only real problem I've had is my WAN link to Comcast goes
down at least every twelve hours. I used to think it was almost exactly
every twelve hours (leading me to think Comcast's DHCP server hated me) but
I have since noticed that the WAN flaps at less predictable intervals. I
can't figure out if it's related to DHCP or not. I can say that nothing out
of the ordinary was going on on my network when this happens. It happens
whether or not anyone is actively using any of the systems on the network.
It can happen when I'm working, browsing, and streaming Netflix or it can
happen everyone in the house is asleep and most everything is down or idle.

One thing that I have learned since I starting this adventure is that it's
in some way related to my D-Link DUB-E100 rev B1 USB NIC. I know that USB
isn't the preferred interface for networking but it's what I had. I'm
currently using a 3.4 GHz P4 Prescott Dell OptiPlex GX620 "ultra small form
factor" desktop for my firewall and it doesn't have any PCI/PCIe expansion
so I'm left with USB. For some reason I had a D-Link DUB-E100 ver. B
(AX88772) adapter laying in a box, since it was on the 8.3 HCL I decided to
give it a try.

Below you'll find the my system, dhcp, and gateway logs for the time that
the link goes down. If you need any other logs or other information I'll be
more than happy to provide it.

system.log: http://pastebin.com/mxuXd55w
dhcp.log: http://pastebin.com/tvAihELQ
gateways.log: http://pastebin.com/2cZqjJBa


So, after watching the logs, thinking, talking on IRC, checking with the
pfSense forums I decided to perform a simple experiment. I swapped the
interfaces, I connected my DOCSIS bridge to the bge0 onboard interface, and
hung my LAN off the USB NIC. Ever since swapping the interfaces everything
has been quiet. I haven't seen a single error in any of my logs.

What are your thoughts? Is is a Comcast issue, an issue with the DOCSIS
bridge, an axe bug, a USB bug, some combination of issues, or something
different entirely? I realize I could just leave everything as is but I'd
like to help solve this little mystery. Also, years ago I was taught it's
bad form not to report potential bugs.

Thanks for your help.

--adam