I don't have the setup.. but I can tell you hows whys and wherefores..
Let me start that Apple is not helpful here, as they deliberately restrict the use of TC to force people to use iCloud.. be clear.. the things you need to do have been removed.
Problem 1. Your IP address.. this is your publically allocated WAN ip address. Is it static? If so this is a cinch.. easy peasy setup. But let me guess.. you don't have nor does your ISP provide static IP's.
Apple do not have a dynamic DNS client in any of their router.. !! (well they do actually for icloud to work, but they made sure you cannot access it).
Step 1. Get a ddns account from a provider that hopefully your security cam has available. Check the manual and see if this is the available and set it up with one of the providers. If not.. you are dead and it is already time to replace the TC with something that does. All cable routers almost without exception these days include ddns clients. Except apple for the reasons stated.
Problem 2. What port do you have to open for access to the camera? Look it up in the manual and tell me. It is usually just port 80.
Step 2 is to forward port 80 to the camera. So the camera must have a static ip in the LAN.. either set ip directly on the camera or lock it via reserved host IP in the airport utility.
Problem 3. Doing this via v6 toyland airport utility is near impossible.. strongly advise using v5 tool.
Step 3. Determine your airport utility version. So if you are using Mountain Lion.. install 5.6 thusly.
How to load 5.6 into ML.
1. Download 5.6 for Lion.
http://support.apple.com/kb/DL1482
Click to open the dmg but do not attempt to install the pkg.. it won't work anyway.
2. Download and install unpkg.
http://www.timdoug.com/unpkg/
Run unpkg on the desktop.. it is very simple.. drag the AirPortUtility56.pkg file over to unpkg.. and it will create a new directory of the same name on the desktop.. drill down.. applications utilities .. there lo and behold is Airport utility 5.6 .. drag it to your main utilities directory or just run it from current location.
You cannot uninstall 6.1 so don't try.. and you cannot or should not run them both at the same time.. so just ignore the toyland version.. the plastic hammer.. and start using 5.6.. a real tool.
