No DNS resolving in LTE-M network
I’m using an EVK-R510M8S (evaluation kit for SARA-R510M8S).
Registration to the network seems to work. I got an IP address and can ping IP addresses. But I got no DNS server addresses so that DNS resolving doesn’t work:
What need to be changed in the setting?
the pinger error 8 you are seeing means no DNS server have been set.
Looking at the at commands for the SARA-R5 module and the response you posted for the
at+cgcontrdp=1command it looks like ip addresses for primary and secondary DNS are missing.
The three IP addresses which are returned are IP, mask and gateway. However the next two entries (primary and secondary DNS) are empty strings.
The only command I’ve seen in the at command list to set DNS ip adress is
AT+UPSD. If that is the correct command and how to use it I cannot say as I don’t have that particular modem to test myself.
Hopefully somebody more knowledgeable can help you with that.
sorry for the late reply, I am definitely not more knowledgable, but I hope that fm’s hints have helped you to find a way to change your DNS servers via the +UPSD command.
If not, I have checked the documentation for your module and the Syntax looks as follows:
The values should be:
<param_tag>: 4 for primary DNS; 5 for secondary DNS
<param_val>: “xxx.yyy.zzz.www” [your desired DNS’s IP]
While looking for the information, I also noticed a topic where another modem did not receive DNS servers from the provider due to a firmware issue, so maybe an update will alleviate the problem as well.
I will also check whether DNS info should normally be provided at that APN for LTE-M SIMs or not.
let us know how it went
the problem is not yet solved - I’m still in discussion with both support teams (U-Blox and Deutsche Telekom).
The problem is that the modem sends in the “ATTACH REQUEST” message the requests for getting the DNS server addresses within the PCO (protocol configurations options):
In the “ATTACH ACCEPT” received by the modem there’s no direct reply to the parameters asked above contained but the information about the DNS server addresses “is hidden” in another PCO container ID - “IPCP”:
So, now we are at the point there U-Blox says:
- “We request the data but we didn’t get an reply to our request ID.”
and Deutsche Telekom says:
- “We send the information.”
And: Yes, both are right.
From my understanding I would say if someone ask with a special request ID the reply must contain this request ID, too. The ETSI standard lists the PCO as optional parameter but this cannot mean that such optional parameters get simply ignored in the reply.
As a workaround I currently configure the DNS server addresses by setting up an own MNO profile but this should only be a workaround for the meantime.
Just as a heads up, I am tracking this topic internally, but I have to rely on feedback from our network people, in order to make any educated statements.
This is taking a little longer than I’d like it to, but thanks again for writing up your troubleshooting in such detail, this definitely helps.
If you’re open for a conversation, I’d love to hear from you about how the whole support journey looked for you and learn about positive and negative aspects that you encountered, so we can do better in the future. You can email me to set up a call, if you’re interested and available.
For anybody experiencing a similar issue:
The problem with the module in question (SARA-R510M8S HW rev. 00B) has been acknowledged by u-blox and they will have it resolved in their next hardware revision 01B.
Unfortunately, there will be no fix beyond Mario’s workaround from u-blox for hw revision 00B.
Thx to Mario for the thorough analysis and help in getting this issue resolved.