I called Centurylinks official tech support line a few minutes ago and they hung up on me after I told them my modem make/model.
I use BTGuard as my personal VPN service and I can't connect to it using my Centurylink connection. I can connect to it on both of my mobile phones and I can connect to it on my laptop when I'm connected to my neighbor's wifi connection (Comcast). Changing DNS servers either on my laptop or via my router config doesn't help.
I also have a VPN tunnel for work and that one works just fine.