My ISP (Frontier communications) has recently implemented new security "features" which requires a backdoor be installed to allow them to make sure I am protected from the evil internets. This back door would allow them to remotely change things in case of a haxor taking over my modem. Without changing my modem's settings, they basically turn off the internet and only allow me to connect to their account page.
I have my modem (which is also a router/AP) set up as a bridge (no routing, no AP) because I prefer to use my Linksys running DD-WRT to perform routing tasks. I can still allow the Linksys perform those tasks with the modem in routed bridge mode, but there is a drawback. The primary one I'm concerned with is that my HA software (HomeGenie) has a companion Android app that allows me to control things from my phone. If I'm at home, my phone automatically connects to WiFi. The software only has 1 IP address that it points to (the external WAN IP) which works fine when I'm outside of my LAN, but when I request the external IP from inside the network (in routed bridge mode), it doesn't know what to do. However, if the modem is in bridge mode, it can perform a loopback which allows the external IP to bounce back inside the network as desired.
At this point, I only have 2 working methods to access my HA software from the app while at home. 1) I can manually type in the internal IP when I'm at home and then switch back to the external when I leave (requires me to write down or memorize the external IP which changes every power outage). 2) I can disable WiFi whenever I want to access HG (this wastes data especially if I forget to turn WiFi back on).
The third option I have been recommended is to use a dynamic DNS service and have something in the network update the external IP automatically (DD-WRT can do this for many services). The down side is that though there are some free services, they either have adds and/or require regularly renewing the subscription. I could pay for a service, but since I had a working setup for over a year, it leaves a bad taste having to now pay for more complexity. Also, it appears that my office blocks many of the these DDNS services which would then mean I have less capability.
The final option is not viable...change ISP. My home is well off the road and my neighborhood (rather rural) has only recently had cable run out our way. I could hook up to cable, but I would have to trust the independent contractor the cable company hires to not cut things up (power, phone, water, irrigation, etc) when digging a trench for the line as well as putting things back in a WAF approved fashion. They'll pay for install, but I know they won't pay for fixing those other things should they screw them up. Oh, and it appears that cable (Wave Broadband) is quite a bit more expensive for a similar service.
All this so I give someone else control over my own equipment. AWESOME!