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What Is a Fixed IP SIM Card? | Private IP and APN Explained
What Is a Fixed IP SIM Card?
A fixed IP SIM card is a mobile data SIM that gives the device it is installed in a permanent, unchanging IP address. Every time the device connects to the cellular network, it is assigned the same IP address. This is different from a standard SIM card, which receives a new, randomly allocated IP address each time it connects.
For most consumer uses – browsing the web, streaming video, general internet access – the IP address a SIM receives does not matter. The device connects outbound to services on the internet, and a changing address causes no problem. However, for industrial routers, IoT devices, CCTV cameras, ANPR systems, SCADA equipment, and any other device that needs to be reached consistently from a central system, a fixed IP address is essential. You cannot reliably connect to a device whose address changes every time it reconnects.
Fixed IP vs Dynamic IP: The Core Difference
Every device connected to the internet has an IP address. This address is what other systems use to find and communicate with it. There are two ways a SIM can be assigned an IP address: dynamically or statically.
Dynamic IP (standard SIM)
With a standard dynamic IP SIM, the mobile network allocates an available IP address from a shared pool when the device connects. The address changes between connection sessions and sometimes during them. The device cannot be consistently addressed from outside the network because its location on the network changes. Dynamic IP SIMs are perfectly adequate for outbound-only data – a device sending readings to a server, for example, does not need an inbound address.
Fixed IP (static IP SIM)
With a fixed IP SIM, the mobile network always assigns the same IP address to that specific SIM. The address is reserved exclusively for that SIM and does not change. This means a central system – a management platform, a VPN server, an NVR, a SCADA controller – can always reach the device at a known, consistent address. This is the foundation of secure remote access for industrial and IoT deployments.
Private IP vs Public IP: Two Types of Fixed IP SIM
Not all fixed IP SIMs work the same way. There are two distinct types: private IP and public IP. The difference determines how the device is accessed and how secure it is.
Fixed private IP SIM (private APN)
A fixed private IP SIM assigns the device a private IP address on a dedicated private APN (Access Point Name). The APN is a closed network operated by the SIM provider. The device connects outbound through this private network to cloud services and management platforms. It is not reachable from the open internet. To access the device remotely – to log into a router, pull footage from a camera, or poll a sensor – an engineer must first connect to the private APN over a VPN. Once connected to the VPN, they can reach every device on the private network using its fixed private address.
This is the more secure architecture and the preferred choice for professional IoT, CCTV, ANPR, and industrial deployments. The device is invisible to the public internet. It cannot be scanned or probed. Access is controlled entirely by the VPN gateway.
Fixed public IP SIM
A fixed public IP SIM assigns the device a publicly routable IP address – one that is directly reachable from the internet. Engineers can connect to the router or device directly without a VPN, using the public IP address and port forwarding rules configured on the router. This approach is simpler to set up initially but carries a higher security risk because the device is exposed to the public internet. Any internet-connected system can attempt to reach it. Public IP SIMs are still used in some legacy installations and in environments where VPN infrastructure is not in place, but professional practice and the requirements of modern ANPR, CCTV, and industrial platforms have moved firmly toward private IP with private APN as the standard approach.
In summary:
Fixed private IP SIM: device has a permanent address on a closed private network. Remote access requires VPN. Device is not reachable from the open internet. Recommended for most professional installations.
Fixed public IP SIM: device has a permanent address on the public internet. Remote access is direct. Device is exposed to the internet and requires firewall hardening. Used in some legacy and simple access scenarios.
What Is a Private APN?
APN stands for Access Point Name. It is the configuration setting that tells a SIM card which network gateway to connect through when it accesses the internet. Every SIM card has an APN – it determines how the device routes its traffic and what IP address it receives.
A private APN is a dedicated gateway operated by the SIM provider that creates a closed network for a specific customer or group of devices. Rather than sending traffic through the standard public internet gateway used by all of the operator’s subscribers, the SIM routes its traffic through the private APN. This creates a private network that is completely separate from the public internet.
All devices on the same private APN can communicate with each other using their fixed private addresses. They can also reach the internet outbound – to send data to a cloud platform, for example – but they cannot be reached inbound from the public internet. Access from outside the private network requires a VPN connection to the APN gateway.
Private APNs are used in industrial IoT deployments, CCTV and ANPR installations, SCADA and telemetry networks, building management systems, and any deployment where device security and controlled access are priorities.
When Do You Need a Fixed IP SIM?
The deciding factor is whether anything outside the device needs to initiate a connection to it. If the device only sends data outbound – uploading readings to a server, sending alerts to a cloud platform – a dynamic IP SIM is often sufficient. If a central system needs to reach the device, a fixed IP SIM is required.
| Use case | Fixed IP needed? | Reason |
|---|---|---|
| CCTV / NVR remote access | Yes | Central NVR or monitoring platform needs to reach each camera or recorder at a known address |
| ANPR camera remote management | Yes | Engineers need secure remote access to routers and cameras for configuration and diagnostics |
| SCADA / telemetry polling | Yes | SCADA controller polls remote RTUs and sensors using their fixed addresses |
| VPN remote access to remote router | Yes | VPN server needs a consistent address to initiate the tunnel, or the router needs a fixed address to be reachable on the VPN |
| EV charge point management | Depends | If connecting outbound to a cloud OCPP platform only, dynamic IP may suffice. If the back office polls the charger directly, fixed IP is needed. |
| Environmental sensor / metering | Usually no | Sensor sends data outbound on a schedule. No inbound connection required. Dynamic IP is sufficient. |
| Remote router management via Teltonika RMS | No | RMS uses an outbound tunnel from the router. Fixed IP is not required for RMS access. |
Fixed IP SIM and VPN: How They Work Together
A fixed private IP SIM and a VPN work together to create secure remote access to industrial devices. The fixed IP SIM gives each device a consistent, known address on the private APN network. The VPN provides an encrypted tunnel from an engineer’s computer (or a central management system) into that private network.
When an engineer needs to access a remote router, camera, or sensor, they connect to the VPN first. Once the VPN is established, they are inside the private network and can reach any device on it using its fixed private IP address. The connection is encrypted. The device remains invisible to the public internet throughout. No device ever needs to be exposed to open internet traffic.
Teltonika routers support multiple VPN protocols natively in RutOS, including OpenVPN, WireGuard, and IPsec. This makes them a natural fit for fixed private IP SIM deployments where VPN remote access is part of the installation design. See our VPN on cellular routers explainer for more detail on VPN configuration options.
Fixed IP SIM vs Roaming SIM: Are They Different?
These are two separate characteristics of a SIM, not an either/or choice. A fixed IP SIM refers to the type of IP address the SIM receives. A roaming SIM refers to the SIM’s ability to connect to multiple mobile networks rather than one.
Most professional IoT deployments need both. A fixed IP roaming SIM gives the device a permanent, unchanging IP address while also connecting to whichever of the major UK networks – EE, Vodafone, O2, Three – provides the best signal at the installation point. This combination is the standard specification for CCTV, ANPR, and industrial remote access deployments in the UK where coverage reliability and secure remote access are both requirements.
Fixed IP SIM vs Teltonika RMS: Do I Need Both?
Teltonika RMS (Remote Management System) provides remote access to Teltonika routers without requiring a fixed IP SIM. RMS works by the router establishing an outbound connection to the RMS cloud platform, creating a management tunnel. An engineer accesses the router through the RMS portal from any internet connection. No fixed IP address is needed because the router initiates the connection outbound.
However, RMS only provides access to the router itself. It does not give access to devices behind the router – a CCTV camera on the LAN, an NVR, a SCADA device, or a serial instrument. If remote access to those devices is required, a fixed private IP SIM and VPN are the correct solution. RMS and a fixed IP SIM are complementary, not competing. Many installations use both: RMS for day-to-day router monitoring and diagnostics, and a VPN over a fixed private IP SIM for direct access to connected devices when needed. Read more in our Teltonika RMS explainer.
Frequently Asked Questions
What is the difference between a fixed IP SIM and a normal SIM card?
A normal consumer SIM receives a different IP address each time it connects to the network. A fixed IP SIM always receives the same address. This makes the device consistently reachable from a central system, which is essential for remote monitoring, CCTV, ANPR, SCADA, and any application where something outside the device needs to initiate a connection to it.
What is the difference between a fixed private IP SIM and a fixed public IP SIM?
A fixed public IP SIM gives the device a permanent address on the public internet, making it directly reachable from anywhere. A fixed private IP SIM gives the device a permanent address on a closed private network accessible only via VPN. Private IP is more secure because the device is not exposed to the public internet. It is the recommended choice for professional CCTV, ANPR, and industrial installations.
Do I need a fixed IP SIM for remote access to my router?
Not always. Teltonika RMS provides remote access to Teltonika routers over an outbound tunnel without a fixed IP SIM. However, if you need direct access to devices connected behind the router – cameras, sensors, SCADA equipment – a fixed private IP SIM and VPN are the correct solution. Many installations use both for different access purposes.
Can I use a fixed IP SIM with any router?
Yes. A fixed IP SIM works with any 4G router that supports APN configuration, which includes all Teltonika, Proroute, Robustel, and industrial routers. The APN provided with the SIM is entered into the router’s cellular configuration. The router then receives the fixed IP address associated with that SIM on every connection.
Does a fixed IP SIM also roam across multiple networks?
It depends on the SIM plan. Millbeck supplies fixed IP SIMs on both single-network and multi-network roaming plans. For professional installations where coverage reliability matters – ANPR, CCTV, remote monitoring – a fixed IP SIM on a multi-network roaming plan provides both a permanent address and automatic network failover. This is the combination most often specified for UK deployments.
Fixed IP SIM Cards from Millbeck
Millbeck Communications supplies fixed IP SIM cards for industrial IoT, CCTV, ANPR, SCADA, and remote access deployments across the UK. Both private IP and public IP options are available, on single-network and multi-network roaming plans. Aggregated data bundles are available for fleet deployments. All SIMs are held in UK stock with next-day delivery available.
Visit the fixed IP SIM cards page to view current plans and request a tariff sheet, or call the team on 0300 124 6181 for advice on the right SIM configuration for your installation. For the full range of IoT SIM options including dynamic IP roaming SIMs, see the SIM connectivity hub.