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Wrong DNS forwarded from EXS62-W to host Linux OS | Telit Cinterion IoT Developer Community

November 3, 2023 - 10:10am, 708 views

Hi all,

we just integrated an EXS62-W module into our product (running Yocto Linux) to have internet access.

After configuring the EXS62-W module, the internet access gets established properly, so our product has internet access. We use the WWAN interface of the module, activating it with the AT^SWWAN command.

On the Yocto side, the network interface has the 192.168.255.20 IP address (looks good, this static IP is also mentioned in the AT command specification). After executing the AT+CGCONTRDP command, we see that the module also got IP+DNS addresses from the network provider. All looks good.

However, we observed that the Yocto OS received 192.168.255.1 as a DNS IP from the phone module and this is not the one that is visible by the AT+CGCONTRDP command. This also causes a problem with our product since the DNS name resolution either does not work or it takes too much time.

If we manually take the DNS IPs from the AT+CGCONTRDP and set them in Yocto then the DNS name resolution works fast.

So looks like the DNS IPs are not "forwarded" from the phone to the Yocto during the DHCP negotiation.

We use NetworkManager in Yocto and in the detailed logs we also see that the DNS address we receive during the DHCP negotiation is 192.168.255.1.

We are not completely sure if the received DNS IP correct or not, but for sure that the DNS name resolution takes too much time with this IP, however if we set the DNS IPs from the AT+CGCONTRDP answer then the name resolution is fast.

Thanks for you comments and help!