3 Disruptions: Direct Cellular IP

Today, with the rapid development of the Internet of Things (IoT) and industrial Internet, an increasing number of devices need to access the Internet via cellular networks. In these application scenarios, how to directly expose the devices to the public network to achieve remote access and control has become a key issue. IP Passthrough is precisely the powerful tool to solve this problem.

So, what exactly is IP direct access? How does it work in a cellular router? What conveniences can it bring us again? Today, let's delve into the core technology of this "network transparent transmission".

What is IP direct access?

• To understand IP pass-through, we first need to understand the "conventional path" for devices to access the Internet in the traditional routing mode. In the vast majority of home and enterprise networks, routers play the roles of "traffic police" and "interpreters". It acquires one or more public IP addresses from the operator, and then through NAT (Network Address Translation) technology, "translates" this scarce public IP address into hundreds or even thousands of private IP addresses, which are allocated to all devices within the internal network (such as mobile phones, computers, cameras, etc.). In this way, all internal network devices share the same public IP "exit" to access the Internet. This approach greatly saves IP address resources, but it also builds a natural "barrier", making it extremely difficult to actively access a specific device within the internal network from the public network.

• IP direct access, as the name suggests, is to completely break down this barrier. It is a special network working mode that allows Cellular network routers to "transparent" or "bridge" all network configuration information, including the public IP address dynamically obtained from the operator, as well as the corresponding subnet mask, gateway, DNS, etc., to a designated device connected to the downstream without any changes. This process is equivalent to the Cellular network router giving up its role as a routing gateway and instead becoming a transparent "bridge".

• Let's understand it with a more vivid metaphor. The traditional Cellular network routing mode is like the switchboard of a large company. External callers (public network data) can only dial the main switchboard number (public network IP), and then the operator (NAT) will transfer the call to the specific employee (internal network device) based on the extension number (port). In the IP direct access mode, the CEO of the company (the target device) is directly equipped with a landline phone. This phone has an independent and publicly available number (public IP), allowing anyone to make a direct call without going through the switchboard for transfer. This "direct" mode endows the target device with unprecedented network autonomy.

The workflow of IP passthrough in Cellular Network routers

The realization of IP direct access is not merely a simple switch. Behind it lies a precise collaborative working mechanism, with each step closely centered around the characteristics of Cellular network.

• Step 1: Acquisition and "Hosting" of Public IP Addresses
  Everything began with the establishment of Cellular network connections. When the Cellular network router is powered on, its built-in cellular modules (such as 5G/4G modules) will search and register with the operator's base station. Subsequently, the router initiates an IP address request to the operator's core network via PPP (Point-to-Point Protocol), DHCP (Dynamic Host Configuration Protocol), or other dial-up methods. After the operator's authentication server verifies the user's identity (via SIM card), it will allocate a public IP address from its IP address pool to this Cellular network connection. In the traditional mode, the router will immediately configure its WAN port using this IP. However, in the IP pass-through mode, the router will temporarily "host" this precious public IP address, waiting for the next allocation instruction.

• Step 2: Specification and binding of the target device
  Users need to manually enable the IP pass-through function in the management background of the Cellular network router and specify a "lucky one" - that is, the downlink device that needs to exclusively enjoy the public IP. This specified process is usually bound through the MAC address (physical address) of the device to ensure uniqueness and accuracy. For instance, a user can input the MAC address of an industrial PLC into the system to declare that this device will become the ultimate recipient of the public IP address. This step is the core of the IP pass-through function, which determines the flow direction of Cellular network resources.

• Step 3: "Transparent transmission" and assignment of network configuration
  Once the target device is specified, the Cellular network router will perform the most critical "passthrough" operation. It will, through the DHCP server function, package the previously "hosted" public IP address, subnet mask, gateway address (this gateway is usually the core gateway of the Cellular network) and DNS server address into a complete network configuration package and send it directly to the bound target device. After receiving this information, the target device (such as IPC, PLC) will automatically configure its own network interface. From then on, it has a "legitimate" public network identity independent of the Cellular network router.

• Step 4: "Bidirectional transparent" forwarding of data packets
  After the configuration is completed, the data flow becomes extremely pure. When the target device sends a data packet to an external server, the source IP address of the data packet is this public IP address, which is directly sent to the Cellular network through the Cellular network router without any NAT address translation in the middle. Conversely, when the external network sends data to this public IP, after the data packet arrives at the Cellular network router, the router will, based on its internal binding table, forward the data packet directly to the target device just like a "Courier" precisely delivering a package. The entire process is completely transparent to the upper-layer application.

• Step 5: Network isolation of other devices
  Enabling IP passthrough also means a kind of "sacrifice". Since the Cellular network router fully allocates the unique public IP resources to a single device, its own routing and NAT functions fail accordingly. Therefore, other devices connected to the LAN port or Wi-Fi of this router will not be able to access the Internet through this Cellular network connection. They are effectively isolated from the public network. This ensures the exclusivity of public IP addresses, but also limits the multi-device sharing capability of Cellular network routers.

Application scenarios of IP direct access

IP pass-through is not designed for daily Internet access. Its value is fully demonstrated in professional and industrial fields, especially in those scenarios with special requirements for Cellular network connections.

• 1. Remote video monitoring and low-latency image transmission
  In scenarios such as smart construction sites, forest fire prevention, reservoir monitoring, and security for temporary events, high-definition network cameras (IPCs) or unmanned aerial vehicle (UAV) video transmission systems need to push real-time video streams to the monitoring center via Cellular network. In the traditional NAT mode, the complex port mapping is not only cumbersome to configure but may also introduce additional forwarding latency and connection instability. IP pass-through enables the IPC to directly own a public IP address. The monitoring center can directly access this IP to obtain video streams. The path is the shortest and the latency is the lowest, ensuring the real-time and smooth performance of the video. This is crucial for emergency command and real-time analysis.

• 2. Industrial Automation and Remote Equipment Operation and Maintenance
  Under the background of Industry 4.0, PLCS (Programmable Logic Controllers), SCADA (Data Acquisition and Control Systems), industrial robots and other devices distributed in various places require engineers to conduct remote programming, fault diagnosis and maintenance. By configuring a Cellular network router that supports IP pass-through for these critical industrial terminals, engineers can access the Web interface or remote desktop of the devices directly through the Cellular network no matter where they are, just as if they were within a local area network. This greatly shortens the fault response time and reduces travel costs. It ensures the continuity of the production line.

• 3. Reliable connection between Internet of Things (iot) devices and cloud platforms
  Although most IoT devices actively report data using protocols such as MQTT, some high-end applications, such as those that need to establish stable P2P (peer-to-peer) connections with cloud platforms or receive downlink instructions from cloud servers for rapid responses, perform better in the IP pass-through mode. It avoids the connection interruption problem caused by NAT session timeout, simplifies the communication logic, and enhances the robustness of the entire Cellular network Internet of Things system.

• 4. Build cross-regional secure VPN tunnels
  For enterprises with multiple branches, building a VPN tunnel through Cellular network is a flexible networking method. However, the IPsec VPN protocol is highly sensitive to NAT traversal, often resulting in failed tunnel establishment or frequent disconnections. Enabling IP passthrough on the Cellular network router of the branch office enables the VPN gateway device to obtain a public IP address, which can perfectly bypass the complexity of NAT-T (NAT Traversal), making the VPN tunnel connection more stable, more secure, and the configuration simpler.

The advantages and precautions of IP direct access
Any technology is a double-edged sword. While IP direct access brings great convenience, it also comes with challenges that need to be treated with caution.

✅ significant advantages:

• Ultimate low latency: Data packets bypass NAT processing, reducing forwarding levels and significantly lowering Cellular network transmission latency, which is of great significance for applications with high real-time requirements.

• Ultimate simplified configuration: Say goodbye to the cumbersome port mapping, UPnP or DMZ Settings, and achieve "zero configuration" public network exposure, greatly reducing the technical threshold for deployment and maintenance.

• Outstanding compatibility: For all protocols and applications that are "allergic" to NAT (such as IPsec VPN, SIP voice, and certain P2P applications), IP passthrough provides the most fundamental solution.

• Ultimate convenient management: The device has an independent public IP address, just like having a fixed network address number, which facilitates asset management, remote diagnosis and centralized monitoring.

⚠️ Important notes:

• Severe security risks: This is the biggest "Achilles' heel" of IP direct access. The device is directly exposed to a public network environment full of attacks, just like leaving the door of home open. Any system vulnerability can be exploited by hackers. Therefore, it is necessary to configure a powerful firewall for the target device, disable unnecessary ports, use strong passwords, and update the firmware regularly to build a defense system in depth.

• Limited IP resources: In the vast majority of cases, operators allocate only one public IPv4 address for a single Cellular network connection. This means that IP pass-through is exclusive, and a router can only provide services for one device at a time.

• Functional compromise: After enabling IP passthrough, the advanced routing functions of the Cellular network router itself, such as multi-device sharing, Wi-Fi Internet access, and firewall filtering, will basically become ineffective. It degenerating into a pure "modem".

  
  

How to enable IP passthrough in a Cellular Network router?

Although the interfaces of Cellular network routers of different brands and models vary, the core configuration logic is largely the same. The following is a general operation process:

• Physical connection and login: Connect the target device to the LAN port of the Cellular network router via an Ethernet cable, ensuring that the SIM card is inserted and the router has been properly registered to the Cellular network. Then, log in to the router's Web management backend via a computer or mobile phone.

• To find dial-up or network Settings: In the background menu, locate the Settings related to Cellular network dial-up, which are usually under tabs such as "Network Settings", "WAN Settings", or "Dial-up Settings".

• Select the working mode: In the dial-up Settings, find the option of "Working Mode" or "Connection Mode", and switch it from the default "Router Mode" to "IP Passthrough" or "Bridge Mode".

• Binding the target device: After the switch, the system usually requires you to specify the target device. You can complete the binding by selecting from the LAN port device list or manually entering the MAC address of the target device.

• Save and restart: After confirming that the configuration is correct, click "Save". The system will prompt that the router needs to be restarted for the changes to take effect. After restarting, the Cellular network router will enter the IP pass-through working state.

📌 Special note: Not all Cellular network packages support the assignment of public IP addresses. Some operators may assign private IP addresses (CGNAT) by default. Before deployment, be sure to confirm with your operator whether your SIM card package supports obtaining public IP addresses; otherwise, the IP pass-through function will not take effect.

IP pass-through, as a seemingly niche but powerful technology in Cellular network routers, is a key link to unlock the in-depth application of the Internet of Things and industrial Internet. It solves the problem of public network accessibility of devices in the Cellular network environment in the most direct and pure way, paving the way for core scenarios such as remote monitoring, industrial control, and secure networking. It not only simplifies the network architecture and improves communication efficiency, but is also an "essential" configuration for the stable operation of many professional-level applications on Cellular network.

Of course, the power of technology requires wisdom to master. While enjoying the "openness" and "convenience" brought by IP direct access, we must always remain vigilant about "security", and through rigorous planning and protective measures, find the best balance between "openness" and "security". With the continuous evolution of Cellular network technologies such as 5G, IP direct access is bound to continue to play an indispensable and important role on a broader digital stage.

If you still have questions about the application of IP passthrough in specific industries or devices, or want to know more detailed configuration steps, please leave a message in the comment section. We will do our best to provide you with more in-depth answers!