[stomachmonkey]

Your Motorola modem is going to provide some routing.

Doubt dynamic DNS is the issue. They are not going to continually change your external IP address. Typically you'll pick up a new address if the broadband, Motorola, modem/router is power cycled and then they sometimes need to be off for a minute or so. For sure the external address will stay current for at least 24 hours.

I would start at the Motorola. Log into it's management pages and set a tunnel to the CISCO. Some broadband routers can be accessed via WIFI some limit access to devices physically connected to it via ethernet.

Most config pages can be accessed from inside the netwrok via a browser at 192.168.0.1, 192.168.1.1. It's typically the lowest number in your network range.

Google your specific model. They usually have a user/pass set up that a lot of techs don't bother changing the default values.