Hi Rhiyadi,
Are you sure that you can reach your DNS (route are set correctly and Firewall rules are deployed for DNS access from your GTM).
So follow this step:
- open 2 CLI window
- on the first CLI Window enter this TCPdump capture
Withi this capture you will see all your dns request:
tcpdump -s0 -vvv -nni 0.0 port 53
- on the secon cli window, lunch the following command:
dig @yourDnsIP www.toto.ch A
when is the fqdn that you want to resolve.
Validate that you see the request in the first window and you pass with the right interface. and validate that FW and route are set correctly for this source IP...
Let me know if you need more details.
regards,