Port Forwarding Doesn’t Work

One of our most common support queries is about port forwarding and the conversation usually goes something like this :-

“My port forwarding doesn’t work”

“The first rule of port forwarding is ‘the router must be accessible from the internet’ – how have you achieved this – for example did you use a fixed IP SIM card?”

“No I didn’t use a fixed IP SIM card – I’m using DYNDNS”

“Okay – so can you access your router over the internet?”

“No – The Dynamic DNS on the router is not working”

“Okay – so which network SIM card are you using?”


“Ah – that will will explain it then – a standard Vodafone SIM card will only give your 3G/4G connection a PRIVATE IP address which means you won’t be able to access your router from the internet and why your DDNS is not working – because in order to use DYNDNS your 3G/4G internet connection needs to have a PUBLIC IP Address.  This will explain why your port forwarding does not work – because you can’t remotely access your router which means that it can’t forward anything”

“But my router has an IP address and I can see it when I visit a website like www.showmyip.co.uk”

“The IP address you can see on www.showmyip.co.uk is in fact the Vodafone PUBLIC IP address on their network – however Vodafone use CGNAT (carrier Grade NAT) which means that behind this PUBLIC IP address are 250 devices with a PRIVATE IP address of which your router is one.  So in order to connect to your router you will have to ask Vodafone to disconnect the other 249 users and re-configure their network to allocate that single, public IP address just to your connection – Good Luck with that!”

“So how do I get port forwarding to work?”

“There are two options – The easy option is to get a Fixed IP SIM card – you can see the tariffs on our website www.3grouterstore.co.uk where you can see options for 3G Fixed IP SIM Cards and 4G Fixed IP SIM Cards – you get one of these and use this with your 3G/4G router and you will get an internet connection with a fixed, public IP address so you can now achieve the first rule of port forwarding and connect to the router over the Internet”

“What is the other option if I don’t want to pay for that type of service?”

“Your only option is to use a 3mobile SIM card and use the APN of 3internet and when the router connects it will request a PUBLIC IP address and if there are some available then your connection will receive a public IP address.  if you are using a 4G router then you will need to set your router to connect at 3G speeds only because this public IP address service with this APN does not work for 4G connections.

You should also be aware that this is not a guaranteed service and Three Mobile may stop this at any time and because it is not a contractual part of your service you will still be liable to pay for the remainder of the contract even though you no longer get a PUBLIC IP address and of course you will then need to subscribe to a Fixed IP SIM card service and visit all your sites to replace the SIM cards.”

We hope that this helps you understand about port forwarding – if you can remotely access your router over the internet and have correctly configured port forwarding then everything should work.  The only other thing to remember is to correctly configure your devices on the LAN – you need to configure IP address, Subnet and IMPORTANTLY you need to include the Default Gateway in your device IP configuration or port forwarding will not work.

If it does not work then please email the support team with screen shots of the following

  1. Status page
  2. APN settings page
  3. Port forwarding settings page
  4. IP settings of your device on the LAN eg DVR/camera