If you need to use the Teltonika TCR100 fro remote access and use port forwarding to connect to your devices on the LAN then the first thing you will need to ensure is that you can connect to the router over the Internet.

Using a standard 4G SIM card obtained directly from the mobile networks (EE, Vodafone, O2, 3 Mobile) will provide your 4G router with an INternet connection, however the IP address of the router will be a private Ip address on the mobile providers network.  This means that you will be unable to connect to the router, nor will you be able to use DYNDNS / DDNS to connect to the TCR100.  This means that Port Forwarding will not work.

Fixed IP SIM Cards

If you need remote access to the TCR100 for example to connect to a CCTV NVR solution or remote access to a home or office service then you will need to use a Fixed IP SIM Card.  This is a service provided by several companies in the UK who have their own interconnects into the mobile networks and overlay a fixed, public or private IP address to the 4G connection.  This enables remote access to your 4G router and enables port forwarding to be used.  If you have a public fixed IP address SIM card service then you can communicate directly to the router from anywhere on the Internet and the TCR100 firewall can handle the security of this public IP connection.  For a more secure (but expensive) solution you can use a prive IP address fixed IP SIM card which means you pay for the fixed IP SIM service and in addition pay for a VPN link into the fixed IP sim network provider in order to access your router and connected devices.  So when you need to connect you first of all create a VPN from your PC to the network and can then access the private IP addresses.

Fixed IP SIM cards are more expensive than normal data SIM cards, but you are paying for the ability to access your router and you cant do that with a normal data SIM.

Fixed IP SIM cards have traditionally been charged with per month inclusive data allowances eg. 1GB per month for £16.00, 10GB per month for £35.00 and 20GB per month for £60.00 per month and if you go over your inclusive allowance then you would end up paying overage charges of around £15.00 per GB.

But now there is an alternative with the arrival of unlimited fixed IP SIM cards which offer a data plan with a fixed, public IP address with a fair use policy of 500GB of data per month for around £85 for a 4G Fixed IP SIM or £130 for a 5G Fixed IP SIM card.  This makes remote access to the TCR100 for large amounts of data alot more competitive than traditional lower data plans that have recently been available.