Replying here because AGL tech support doesn't have a clue and frankly neither do many people posting here.
Firstly, some important information. AGL uses CGNAT (Carrier Grade Network Address Translation). To put it in simple terms, imagine you share a house with 4 other people. As far as the world is concerned, all 5 of you have the same address and when mail comes to your house it is up to someone to sort it to make sure that the right mail gets to the right person. CGNAT is effectively the same thing your internet address (IP) is shared among tens if not hundreds of AGL internet subscribers and AGL has a sorting machine (router) which sorts internet traffic so that it reaches the right place. Now imagine mail comes just addressed to the house, there is no way to know who it should go to and the router isn't going to let everyone see it (imagine it had important details in there).
This means that no amount of dynamic dns, port forwarding or firewall rules on the users end will ever get outside traffic into your home network. You need AGL to turn off CGNAT - but don't mention this they won't have a clue what you are talking about. Instead you need to ask for a static IP - this isn't the same thing but AGL charges $7.50 for this service. When you ask for a static IP, tech support will assume you are running a business and try to get you on a business plan. No, I'm not running a business, there are many services today that need outside traffic to be able to come into the home e.g. google home, security cameras, etc.
You don't need to believe me, go into your router and if you look at the "supposed" address that AGL provides you. It will be in the 10.X.X.X private IP pool - this is akin to your internet address being "Unit 5"; that's great but Unit 5 of what address?
Here are some tips when talking to tech support:
1. Don't mention CGNAT - they have no clue what you are talking about.
2. Ask for a static IP.
3. Tell them that you are not running a business (otherwise you will pay costly business internet rates).
Now, once you get your static IP, AGL tech support still has no idea how their product works.
Normally, your static IP is configured from your internet providers end using a protocol known as DHCP. In basic terms, you home router goes "Hello AGL, I'm John Smith and I need an address" and AGL responds "Okay John Smith, I see you have a static IP, your address is 123.456.789.000".
However, for whatever reason this is not how it works with AGL. Once your static IP gets provisioned (you'll either get a text or an email), your internet will go down and you won't have a clue why. Calling up tech support will be fruitless the only thing they know how to do is to turn off your static IP (which will give you your internet back).
Basically, you need to manually put your static IP address into your home router (good luck with that if you aren't using an AGL provided device they can't help you with instructions) - this is akin to the conversation going "Hello AGL, I'm John Smith and I know my address is 123.456.789.000". You will also need to manually configure your DNS servers in your router.
If you get this far, you have probably spent about 4 hours over 2 days over the telephone with tech support like I did. Unfortunately for me, there's some kind of incompatibility between my router and this bizarre way that AGL is set up. It works for around 15 minutes and then I need to restart my router for it to work for another 15 minutes. It's frustrating, their tech support has no clue about basic internet networking concepts and if your anything like me you will leave AGL internet 4 days after you signed up with them.
