How to configure the APN on an IoT SIM
A misconfigured APN is the number-one reason a device does not connect after install. This guide shows the right flow on industrial routers, modems via AT, and the checks to rule out other problems.
- 1
Get the exact APN from the provider
Usually something like m2m.iot, iot.cards.privado, or similar. Note username, password (if any), and PDP type (IP, IPv6, or IPv4v6).
Tip: If they will not give you the APN in writing, bad sign. Insist on documented answer.
- 2
Configure via web UI (router)
On industrial routers (Teltonika, Robustel, Cradlepoint), go to Network -> Mobile -> APN, enter the parameters, save. Restart the mobile interface to force re-attach.
- 3
Configure via AT command (modem)
AT+CGDCONT=1,"IP","your.apn" creates the PDP context. Then AT+CGACT=1,1 to activate. With credentials, AT+CGAUTH=1,1,"user","pass".
Tip: Some modems use AT+QICSGP (Quectel) or AT+UPSD (u-blox). Check the vendor's AT manual.
- 4
Verify the context is active
AT+CGACT? should return 1,1. AT+CGPADDR=1 gives the assigned IP. If the IP is 0.0.0.0, the context is not really up.
- 5
Test real connectivity
Ping 8.8.8.8 (on public APN) or an IP in your private network (on private APN). If ping fails but you have an IP, check the carrier firewall or wrong APN.
- 6
Persist the configuration
AT&W or AT+CGDCONT in a persistent profile per vendor. After reset the modem should boot with the correct APN with no intervention.
Common pitfalls
- ·Trying a private APN with a SIM provisioned for public (will not work until the provider updates the HSS).
- ·Using IPv4 when the network requires IPv4v6 (modem stalls on attach).
- ·Not rebooting after changing APN: many modems do not pick it up hot.
- ·Assuming failed ping means broken SIM: often just the carrier firewall.
Checklist
- ☐Exact APN received in writing
- ☐Configured via UI or AT
- ☐PDP context active with valid IP
- ☐Connectivity tested to a real target
- ☐Configuration persisted and validated after reboot
FAQ
How do I change APN on a remote SIM?+
If the provider supports it, OTA via SIM Toolkit. On the modem: send AT through remote console or router manager. Without remote access, on-site visit.
What happens if I set a non-existent APN?+
The modem fails attach (+CEREG: 0,3 or similar) and stays without data. With AT+CMEE=1 you get clear error messages.
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