I’ve always found dual-SIM smartphones incredibly useful, but one issue that kept frustrating me was how APN settings would conflict between different carriers. If you’ve ever experienced internet dropping, one SIM losing data, or connectivity issues when switching between SIMs, you’re not alone.
Dual-SIM conflicts with APN settings are more common than most people realize. Different carriers use different APN settings, and when two networks operate on the same device, one APN can interfere with the other. In this guide, I’ll break down why these conflicts happen and how to fix them.
Why Dual-SIM Phones Have APN Conflicts
1. Each Carrier Uses Different APN Settings
The first problem I faced was realizing that each SIM card had its own unique APN settings. This meant:
- Carrier 1 (SIM 1) might use IPv4, while Carrier 2 (SIM 2) requires IPv6.
- One network may require PAP authentication, while the other needs CHAP or none at all.
- APN types like default, supl, dun, and ims may conflict, causing SIM switching problems.
2. One SIM Might Override the Other’s APN Settings
Many dual-SIM devices automatically set the default APN based on the primary data SIM. This results in:
- The secondary SIM not being able to use mobile data.
- The APN settings of one SIM disappearing or getting replaced by the other’s APN.
- Connectivity issues when switching between SIMs manually.
3. Dual-SIM and 5G/VoLTE Conflicts
With 5G and VoLTE (Voice over LTE) now common, I noticed that some carriers require specific APNs for VoLTE or VoNR (Voice over New Radio). When using two SIMs, this can cause:
- One SIM losing VoLTE capability because the IMS APN gets overridden.
- 5G connectivity issues on one SIM when both are active.
- VoNR not functioning if the second SIM does not support it.
4. Some Devices Prioritize One SIM Over Another
Some manufacturers design their dual-SIM phones to prioritize SIM 1 over SIM 2. This means:
- SIM 2 might not get internet access if both SIMs are active.
- The device may reset the APN every time a different SIM is set as primary.
- APN changes may not save correctly when switching SIM slots.
How to Fix Dual-SIM APN Conflicts
1. Set the Correct APN for Each SIM
Most modern dual-SIM phones allow you to set separate APN settings per SIM. Here’s how:
- Go to Settings > Mobile Network > SIM Settings.
- Select SIM 1 and enter the correct APN settings.
- Select SIM 2 and enter its specific APN settings.
- Ensure that each SIM’s APN is saved separately.
- Restart the phone and check if the settings remain.
2. Disable Automatic APN Switching
Some phones automatically switch APNs when you change the default data SIM. To prevent this:
- Go to Developer Options (enable by tapping Build Number 7 times in About Phone).
- Look for Automatic APN Switching and disable it.
- Set a manual APN for each SIM in the network settings.
3. Manually Configure APN Protocol and Authentication
One issue I ran into was conflicting APN protocols (IPv4 vs. IPv6). If one carrier forces IPv6 while the other uses IPv4, the device may struggle to keep a stable connection. Fix it by:
- Setting IPv4/IPv6 manually instead of default auto-selection.
- Ensuring PAP/CHAP authentication matches the carrier’s requirements.
- Manually configuring APN types (default, supl, dun, ims) correctly.
4. Force 4G/5G Mode for Each SIM Separately
Some phones don’t allow both SIMs to use 5G simultaneously. If you notice one SIM losing connection when using 5G:
- Set SIM 1 to 5G/4G Preferred and SIM 2 to 4G-only.
- Test whether switching between networks stabilizes the APN.
- Disable 5G on the secondary SIM if conflicts persist.
5. Reset Network Settings for Each SIM
If nothing works, resetting the network settings may resolve the issue:
- Go to Settings > System > Reset > Reset Network Settings.
- Reset each SIM separately, then reconfigure APN settings.
- Restart the device and test each SIM individually.
Common Dual-SIM APN Issues and Fixes
1. One SIM Has No Internet
- Why it happens: The device defaults to one APN, preventing the other SIM from working.
- Fix: Manually set an APN for each SIM and restart.
2. APN Settings Keep Resetting After Switching SIMs
- Why it happens: Some carriers override manual APN entries when switching primary data SIMs.
- Fix: Disable automatic APN updates in Developer Options.
3. Dual-SIM VoLTE/VoNR Not Working
- Why it happens: VoLTE/VoNR requires specific IMS APN settings, which may get erased.
- Fix: Set the correct IMS APN manually and test VoLTE activation.
4. SIM 2 Cannot Use 5G
- Why it happens: Some phones restrict 5G to only one SIM slot at a time.
- Fix: Switch SIM slots or disable 5G on the secondary SIM.
Future Solutions for Dual-SIM APN Conflicts
1. eSIM & Network Profiles
- More carriers are moving to eSIM, allowing seamless network switching without manual APN configuration.
2. AI-Based APN Management
- AI-driven automatic APN configuration could detect and resolve APN conflicts in real-time.
3. Unified 5G Dual-SIM APNs
- Some manufacturers are working on dual-5G SIM configurations that allow both SIMs to work seamlessly.
Conclusion
Dealing with dual-SIM APN conflicts can be frustrating, but understanding why these issues happen makes it easier to fix them. By setting APNs manually, disabling automatic switching, and adjusting network modes, you can stabilize your dual-SIM connections.
Quick Summary
- Dual-SIM phones often face APN conflicts, leading to no internet, switching issues, or one SIM not working.
- Some carriers enforce unique APN settings, which may override manually entered configurations.
- 5G and VoLTE settings can interfere with APN configurations when both SIMs are active.
- Some devices prioritize one SIM over another, causing default APN resets.
- Solutions include setting APNs per SIM, disabling automatic APN switching, and manually configuring network settings.
If you’ve had similar issues with dual-SIM conflicts, try the fixes above and let me know which one worked for you!
