So... after my last post, I thought it was only appropriate to share how CenturyLink sucks.
First, they gave me an activation date, but no activation time. When during this magical date was the activation to occur? I spent about 15 minutes on the phone (most of that time waiting on hold) before I was given a time (5pm). If they had just included that information in my order confirmation emails, they could have saved us both some time. (Granted, I could have been patient and just seen if it was working the day after, but still.)
Next, during the days before the activation date (they call it an "installation date", by the way), I tried to get my modem sort of "pre-configured". I wanted it to be ready-to-go when they were ready to activate it. So, prior to today (my activation and call-to-find-out-what-time day), I spent a while fighting with it on Firefox - the built-in configuration pages wouldn't work on Chrome. CenturyLink refused to help with anything other than "basic setup", which apparently turning it into a simpler device (by disabling wireless, DHCP, et cetera) wasn't considered "basic setup". Odd.
Anyhow, I decided to contact Actiontec - the manufacturer of the modem. Similarly unhelpful, they at least pointed me in the right direction when they said it was caused by security settings in Chrome. I discovered that Opera worked fine with it.
Able to save my settings (the part that Firefox couldn't do on some pages), I made it my own. I turned on DMZ, tried disabling NAT, and a few other things.
Ultimately, once it was activated, I was locked out of my modem. Not necessarily CenturyLink's fault, but still annoying, nonetheless. I had to do a factory reset (losing all of my settings in the process), and re-setup what I had done.
I discovered that disabling NAT disables Internet access (something that Actiontec had warned me about), but that turning on DMZ really seemed to do nothing, when (in theory) it should have forwarded all unused/unassigned ports to the IP address I specified (as consumer devices do).
It didn't work. Instead, I just forwarded all ports (1-65535) to my firewall, and it's working fine now. So I take to Twitter with my discovery. CenturyLink responds, offering to help. Huh? I let them know (briefly) that they wouldn't help, although that doesn't really matter now.
Note: I realize that some of my issues were due to lack of technological literacy, as well as impatience. Nonetheless, CenturyLink's refusal to help didn't make things any better. Better than Mediacom, but still far from "good".