Good write up. From what I can gather, it sounds like my modem lan ports were set to auto, but because my wan port on the router was set at 100mb/FullDuplex it would not negotiate a connection and the modem was falling back to half duplex. After I set the router to auto configure, both devices were able to talk and negotiate a true 100mb/FullDuplex connection. Very helpful for configuring devices in the future.
Hey TPS, noticed you got that firewall message in the middle.
I've found that entering "no event" in the CLI will disable those messages from spamming you during that session alone. Log out, log back in, and you can monitor the events again.
So if you ever need a clean capture (or just need stuff to NOT scroll off your PuTTY session on a misbehaving router), give that a try!
You can toggle default events back on by entering "events" (no quotes) at the enable prompt. Hope that saves you a logoff/on someday.
We did some testing awhile ago on the 3120 platform, WAN to LAN varied with NAT on/off, but we were seeing anywhere from 15-18mbs throughput.