Hello,
Apologies for a late reply.
It would be great if you could provide a bit more information.
What firmware is installed on your RUTX11?
Which DNS servers are currently in use, and could you provide details about your configurations?
Are the DNS issues specific to LAN clients, or the RUTX11 itself is unable to resolve hostnames?
Could you please navigate to System → Maintenance → Troubleshoot → Diagnostics section and perform nslookup? Try putting google.com as the address and share the output here.
Also, I would recommend taking a look at the forum posts here, here, and here.
Kind Regards,