nRF9160: not retrieving DNS servers with IPV6

Question

I am currently working on a project with a nRF9160 and in the very early stages of evaluation. 
 I have a few, hope not too many questions that I hope can be answered here, if it is not too much trouble. I am starting fresh with the nRF9120SK, but do have prior experience with the nRF51 and nRF52 chips, though it was several years ago, the development environments were quite different, especially with the added Zephyr libraries. Ultimately this project might be implemented as a serial_lte_modem using another MCU that handles the main logic of the device. 
 I have been searching on these forums and internet search engines today and yesterday quite a bit and have a few unresolved questions. 
 Using a macOS Big Sur development environment, I can go into specifics but it is not related to the current question. I am currently using the example at /opt/nordic/ncs/v1.4.1/nrf/applications/serial_lte_modem 
 Built with the command west build -b nrf9160_pca10090ns 
 Is there a difference between these two commands? Does it result in the same build? west build -b nrf9160_pca10090ns west build -b nrf9160dk_nrf9160ns 
 I am using the SDK version v1.4.1, modem software version 1.2.3 (I had some trouble updating it, it was in a very early 0.6.x.x-alpha state when I received the PCB). Following this guide https://devzone.nordicsemi.com/f/nordic-q-a/53208/updating-nrf9160-modem-firmware-through-the-command-line I was able to bring it up to date after a few hours of frustration. If anyone is interested in how I brought this up to date I can share the procedure, but I had to use the python nrfjprog wrapper to do it. 
 I have a nRF9160DK and am using a MVNO SIM operating in Japan with KDDI by au. 
 I am going to provide the output of some commands so you can see the results. 
 It appears that this SIM only supports IPV6, is there such a thing? 
 Here is the output of some of the network information. 
 +CGPADDR: 0,"0000:0000:0000:0000:0000:004A:XXXX:9801" (removed some information for privacy) +CGCONTRDP: 0,,"ims","","",,,,,,,1500 
 
 I have another SIM here (I have to manually set the APN) that retrieves an IPV4 address and DNS servers with the following output. 
 I have the following output with that SIM card, I have to use AT+CGDCONT=0,"IP"," iijmio.jp " to set the APN before enabling the modem. 
 If you would like to add this SIM card to the list of automatically configured APNs please let me know, I am more than happy to provide details. 
 +CGDCONT: 0,"IP","iijmio.jp","XXX.XXX.123.XXX",0,0 ( removed some information for privacy) +CGCONTRDP: 0,,"iijmio.jp","","","202.232.2.2","202.232.2.3",,,,,1500 
 
 I am using this guide at 
 https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.4.1/nrf/applications/serial_lte_modem/doc/slm_description.html 
 to test a connection to google.com. I can connect fine with the second listed SIM card that retrieves an IPV4 address. 
 I can not connect with the first SIM that retrieves an IPV6 address, it has no DNS servers. 
 I found information that I can manually specify DNS servers, but I don't know how to do this with AT commands. 
 https://devzone.nordicsemi.com/f/nordic-q-a/50029/nrf9160-modem-firmware-v1-0-0-setting-custom-dns-server/235419#235419

aldras · Accepted Answer

Hi Didrik, I finally got a hold of a device that works with the SIM chip in question above, of course it was an issue with the APN information. Although I thought LTE did not require authentication, this SIM chip does, and so does another that I have. Maybe authentication is still something used by providers in Japan? It was not an IPv6 issue, this runs IPv4, and retrieves an IPv4 address. For some reason the nRF9160 automatically retrieves the APN "ims" and that IPv6 address, I don't know why, but would be happy to share modem traces if you would like to try to track down the issue. It is possible the network is providing this "ims" APN, but it is intentionally incorrect? Anyway, for reference in addition to the AT+CGDCONT to set the APN, I also needed to use the AT+CGAUTH to set the authentication information. Here is some information from the manual, I will copy here... This is from this manual, I think it is not the current SDK, but this command appears to not have changed. I changed a little of the information below, instead of using "PAP"/"CHAP" I put a 1 in place, and changed the CID number to 0. I hope this information helps some other developers who run into needing to use authentication for their SIM chips. infocenter.nordicsemi.com/.../nrf91_at_commands_v1.2.pdf 6.16 Define PDN connection authentication parameters +CGAUTH The +CGAUTH command specifies authentication parameters. For reference, see 3GPP 27.007 Ch. 10.1.31. 6.16.1 Set command The set command specifies authentication parameters for a PDN connection specified by parameter . Syntax: +CGAUTH=[,[,[,]]] The set command parameters and their defined values are the following: 0–11 0 – None. Username and password are removed if they have been specified. 1 – PAP 2 – CHAP String String The following command example sets authentication parameters for CID=0 context: AT+CGAUTH=0,2,"username","password" This resolves this issue, after all it was not a DNS issue, it was an issue of not supplying the correct APN information to the nRF9160. It appears the nRF9160 can not automatically figure out these APN settings, if you would like to add this to the nRF9160 so it can correctly auto configure these devices please let me know and I will be more than happy to share information about the SIM chips that I run across during development. I am leaving this case open for a little bit so this final message is seen, I will mark it as resolved soon. Thanks for all the support on this topic!

nRF9160: not retrieving DNS servers with IPV6

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