As part of the KPN Mobile Core migration (Phase 3), it is critical that your Teltonika routers are not configured with hardcoded SIM IP addresses.
After the migration, devices will no longer retain a fixed IP at the device level, and any static or manual IP configuration may cause connectivity failures.
Why this matters
- Following the migration, KPN is introducing an IMSI-based NAT function.
- Each device will be assigned a private dynamic IP locally.
- NAT ensures that the external-facing IP (used by backend systems) remains unchanged, whilst the IP seen locally by the device itself will differ.
- If a fixed IP is hardcoded in your Teltonika router or VPN configuration, it will no longer be valid after migration.
This could prevent devices from reconnecting, forming VPN tunnels, or transmitting data.
⚠️ Important: Always configure your Teltonika router to obtain its IP automatically (DHCP).
Never enter the SIMPro IP address manually.
Example from a test SIM
Using a Teltonika router with a KPN SIM:
- IP address shown in SIMPro: 10.232.86.225
- IP address seen by the Teltonika device: 10.0.191.147/32
👉 This difference is expected and is the result of the NAT function.
Figure 1: SIMPro showing the IP address assigned to the SIM
Figure 2: Device view in the Teltonika router management platform showing the IP address actually used by the device
What you need to do
- Ensure your Teltonika router does not contain a hardcoded IP address.
- Check your router’s WAN/Cellular interface settings — confirm they are set to Automatic / DHCP.
- If using IPSec VPNs, configure the source IP as the WAN interface, not a static SIM IP.
- Do not reference the IP displayed in SIMPro within your device configuration.
Key reminder
After migration:
- Devices will receive private dynamic IPs.
- KPN’s NAT function ensures that external-facing IPs remain stable for backend systems.
- The local IP shown in the router will differ from the SIMPro IP.
- Any configuration relying on the old fixed SIM IP will no longer work.
✅ Expected behaviour
After the KPN migration (Phase 3):
- The IP address shown in SIMPro and the IP address visible on the device should be different.
- This difference is intentional and caused by KPN’s IMSI-based NAT function, which assigns each SIM a private dynamic IP whilst maintaining a consistent external-facing IP for backend systems.
⚠️ Unexpected behaviour
If the IP address shown in SIMPro is the same as the IP shown on your device, this likely means:
- The device has been manually configured (hardcoded) with the SIMPro IP, or
- The device is not obtaining its IP dynamically (DHCP), or
- There is a configuration issue preventing the NAT function from working correctly.
In this case, the device may fail to reconnect or transmit data after migration.
Support
If you need help checking your Teltonika router configuration, please contact our Network Team at support@wirelesslogic.com.