DNS resolution issues with 4.3.3 & 4.3.4 on R201

I had a whole bunch of managed routers come back from the field all of the sudden due to "not working".  After investigation the issue was due to upgrading the firmware and the new firmware seems to have DNS resolution issues.  For now it seems that disabeling DNS proxy under the LAN settings resolves the issue.  Anyone else seeing this or have other insight on this issue?

We didn’t see such issue in our lab. Please send the configuration and syslog message of the device("not working") which has DNS issue( My Email Id: niraj.mahapatra@cambiumnetworks.com).

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We lost 78 devices to this issue yesterday as well.

After analysing  device syslog and screen capture .


  1. LAN Side PC  received two DNS address (  Primary DNS: 168.11.1( R201 as Proxy DNS),  Secondary DNS: Proxy DNS of Up Link network/Router .). In this case, DNS query should be resolved by  secondary DNS( even if the query is not resolved/responded by primary DNS.
  1. There is no secondary DNS in IP WAN interface.


  • Use Google DNS server (, as primary  DNS in DHCP server configuration of Uplink network/ Router. DNS Query will resolve even if proxy DNS is not working properly.WAN_Interface_Status.jpg
  • Update Secondary DNS IP in  DHCP server configuration of Uplink network/router and configure   Google DNS ( or proxy DNS .

As we are unable to replicate this issue in our Lab. Please send Packet capture of LAN side PC  to analyze DNS transaction.   

Did you see this issue with default config mode in 4.3.4-R8 or 4.3.3 image?