Cellular WAN Setup with Dual SIM Failover
Introduction
The Cellular WAN Dual SIM Failover Topology is designed to enhance Internet connection reliability by utilizing two SIM cards from different mobile network service providers. This setup is crucial for applications requiring uninterrupted internet access, such as remote monitoring, IoT deployments, telematics, smart transportation, energy management, and industrial automation.
Dual SIM failover is a highly valuable feature in D-Link M2M devices. When the primary SIM's network experiences downtime, weak signal strength, or service interruption, the device can automatically and seamlessly switch to the secondary SIM. This failover mechanism ensures continuous data transmission and system availability, significantly boosting overall system reliability and resilience. The automated nature of this functionality reduces the need for manual intervention or on-site maintenance, thereby minimizing downtime and lowering labor-related expenses.
In essence, dual SIM failover enhances the robustness of connected systems and provides organizations with a reliable, efficient, and cost-effective connectivity solution.
This document also illustrates the configuration of a D-Link M2M router using dual SIM cards to implement automatic failover. When the SIM A connection is lost, the device automatically switches to SIM B, ensuring seamless network connectivity. This feature is particularly suitable for high-availability use cases such as remote monitoring and data collection.
Please note that this example is based on specific prerequisites and topology. D-Link does not guarantee compatibility with all platforms or clients.
Prerequisites
1. An M2M device with dual SIM card slots.
2. 2 x SIM cards:
- First, ensure that both SIM cards can provide network connectivity for both operators.
3. At least one device:
- A PC, laptop, or tablet is required to configure the M2M device.
- This feature is applicable to the following models:
DWM-314-G, DWM-311-GP, DWM-314-GP, DWM-313, DWM-530-T, DWM-550-G, DOM-530-TSO, DOM-550-GSO, DTM-550-G
Topology
The D-Link M2M device has 2 SIM card slots for failover/backup. When the connection from Cell 1 or Cell 2 is lost, the M2M device will automatically switch to the 4G connection from Cell 1 to Cell 2 or from Cell 2 to Cell 1.
1. Cell 1 is disconnected:
D-Link M2M device with 2 SIM card slots. SIM A is for MNO 1 and SIM B is for MNO 2. On the laptop, we use the ping function to check the network connection. When the WAN 1 connection is lost, the M2M device will automatically switch from SIM A to SIM B.
2. Cell 2 is disconnected:
When the Cell 2 connection is lost, the M2M device will automatically switch from SIM B to SIM A.
Note: Before starting this configuration, please make sure the basic network settings of the D-Link M2M device are configured properly.
Configuration
1.SIM-A or SIM-B First Configuration:
Go to Basic Network > WAN & Uplink > Connection Setup tab
Setup Cellular WAN Type Configuration. Here is the SIM-A First example, as shown below.
| Item | Descrption |
|---|---|
| WAN Type | From the dropdown box, select Cellular WAN Connection |
| Preferred SIM Card |
Choose which SIM card you want to use for the primary connection When SIM-A First or SIM-B First is selected, it means the connection is established first by using SIM A or SIM B |
| Auto Flight Mode | Default is disabled the Auto Flight Mode |
| SIM Switch Policy | Click the Policy Setting button to define the SIM Switch policy or browse the current policy settings as default |
2.Network Monitoring Configuration:
Set up Network Monitoring Configuration. Here is the example, as shown below.
| Item | Descrption |
|---|---|
| Network Monitoring Configuration | Check the Enable box to activate the network monitoring function |
| Checking Method | Choose ICMP Checking to detect A WAN link |
| Loading Check |
Check the Enable box to activate the Loading Check function. Enable Loading Check allows the gateway to ignore unreturned DNS queries or ICMP requests when the WAN bandwidth is fully occupied. This is to prevent a false link-down status. |
| Check Interval |
Query Interval defines the transmitting interval between two DNS Query or ICMP checking packets. Value: Set 5 seconds. |
| Latency Threshold |
Latency Threshold defines the tolerance threshold of the response time. Value: Default 3000 mini-seconds. |
| Fail Threshold |
Fail Threshold specifies the detected disconnection before the router recognizes the WAN link down status. Value: Set 5 times. |
| Target 1 |
Other Host: Enter an IP address to be the target. Set Other Host, IP: 8.8.8.8 |
| Target 2 | Set None |
| Save | Click the Save button to save settings |
Test Result
Please configure the device according to the above environment and configure them, then validate to ensure everything works as expected.
1. Expected Test Results:
- When SIM A's 4G connection is disconnected, the M2M device will automatically switch to SIM B, and the 4G connection will reconnect to the base station and function normally.
2. Test Results:
- We take the M2M device to conduct the following test.
- SIM A/B configuration settings: See above section.
- When the SIM A Internet connection is disconnected (manually removed SIM A), the M2M device switches from SIM A (FAR Eastone) to SIM B (Chunghwa Telecom).
- Due to testing environment limitations with cellular disconnection, we manually removed SIM A to simulate disconnection and confirmed that the cellular network successfully switched to SIM B.
