TX Underrun

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.

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