Ever since I set it up, once my pfSense box has been running for a while it seems I will plug in the monitor to find two, three, or more messages about TX underruns, such as
dc0: TX underrun -- increasing TX threshold
However, my network started being slow to respond on the 6th, going so far as to drop one packet when I pinged Google. The LAN side was just fine. Yesterday I plugged the monitor into the router to see what was up, as I was unable to find a system log of console messages. The last message was
dc0: TX underrun -- using store and forward mode
My understanding is that this is why it became slow. This machine is not screaming fast by any means. It has 504 MB of RAM and a 499 MHz Pentium 3. Looking in the WAN interface settings, I realized I had misunderstood and set the wrong MTU. I saw the size for PPPoE, and given its mention in my modem’s configuration, I had understood, incorrectly, that my router would use PPPoE. (Even though the WAN interface was visibly set to DHCP on that very page.) I now do not know why I felt the need to set this manually, and as I reread my modem’s status page I feel more and more mystified as to how I came to that understanding: PPP on the modem (Public IP for LAN device). I left the field blank as to allow pfSense to set the MTU, and my WAN connections are speedy again.