Issue related to APN names

Question

I am using simcom900 modem,I am successfully able to establish GPRS connection and send data from my module to server.I am using 2g Airtel SIM and I have given APN name as "airtelgprs.com".I have also tried by giving different APN names which are not related to airtel network then also I could establish connection and transfer data to server.

Please let me know how is this possible?

Answer 1

With the SIM unlocked, try entering

AT+CGDCONT?

Now you should see all the stored contexts, something like this:
+CGDCONT: 1,”IP”,”airtelgprs.com”,”0.0.0.0″,0,0
+CGDCONT: 2,”IP”,”other apn”,”0.0.0.0″,0,0
+CGDCONT: 3,”IP”,”other apn2”,”0.0.0.0″,0,0

Now try to activate each context in turn

AT+CGACT=1,1 (first parameter activates the context, 2nd parameter defines which context is activated)
You should get "OK" if the activation was successful. Now deactivate context number 1 with

AT+CGACT=0,1 OK

Now, try to activate one of the wrong apns:
AT+CGACT=1,2 You should get something like:
+CME ERROR: no network service
(switch on error reporting with AT+CME)

Now delete the stored contexts with the correct APN, by setting them to empty:
AT+CGDCONT=1,"","","",0
OK
Check that they are gone:
AT+CGDCONT?
(get only contexts with wrong APNs)

Now try your AT command again, with a wrong APN:
AT+CSTT="some wrong apn" etc.

You should hopefully see that it doesn't connect. If it doesn't connect, maybe AT+CSTT always connects on the saved context number 1, even if you give it a different APN. It should be easy to test that theory by playing with AT+CGDCONT and the stored contexts.

AT+CGDCONT and AT+CGACT are standard AT commands, you can find the full reference in 3GPP TS 27.007.

Answer 2

Most of the operators are using special features (usually called APN Redirection) on their networks to fix wrong APN names to some default APN name. E.g. when you are trying to establish PDP using APN name "iternet" it will be automatically redirected to APN name "internet". So, it seems that you have faced with that behaviour.

Answer 3

APN redirection is active for your provider where your APN will be corrected automatically to some default APN or selecting the one you have subscribed based on your subscription profile in HLR.

Answer 4

You face this issue, or rather lack of an issue, most probably, because Airtel doesn't check for APN at all while connecting via GPRS. I have tested this with different SIM cards, and different SIM plans. Operators that strongly check for APN- 1. Idea 2. MTNL 3. Vodafone Note: All the operator info mentioned here is stricly for the region on India. I don't have experience of other regions.