Forum Discussion

mouverthewanderer's avatar
mouverthewanderer
Icon for Nimbostratus rankNimbostratus
Jul 24, 2023

UDP DNS listener doesn't resolve DNS query but TCP DNS listener can

I'm using an F5 GTM R5000 Series device I have configured the following components:  - Configured Self-IP, ensuring no Firewall block UDP and TCP port 53. - Created data center, Server and Virtual...
security
  • whisperer's avatar
    whisperer
    Jul 25, 2023

    If using the same Self IP as the GTM listener, make sure port lockdown permits both udp and tcp 53. Also check the DNS profiles attached to both listeners for UDP and TCP to make sure they are both the same. Also check subnet mask and IP address for any typos.

Paulius's avatar
Paulius
Icon for MVP rankMVP

mouverthewanderer Can you validate if the GTM is indeed receiving the UDP request? You should be able to use the following to validate that it is arriving at the F5.

tcpdump -ivvv 0.0 udp port 53

mouverthewanderer's avatar
mouverthewanderer
Icon for Nimbostratus rankNimbostratus
Jul 25, 2023

I used tcpdump on F5 OS and see that UDP packets didn't reach DNS listener IP. Thanks