For more information regarding the security incident at F5, the actions we are taking to address it, and our ongoing efforts to protect our customers, click here.

Forum Discussion

TheRedBaron's avatar
TheRedBaron
Icon for Nimbostratus rankNimbostratus
Nov 10, 2019

APM VPN Clients - DNS Resolution Failing Intermittently

Hi all,   I've run into an issue with my remote users who are getting intermittent connection problems which seems to be related to DNS resolution failing. They're a mix of Windows 7 and Windows ...
tcpdump
Dave_W's avatar
Dave_W
Icon for Employee rankEmployee
Nov 12, 2019

Hello, If you restart the DNS relay proxy does it resolve the issue? Also if you do a tcp dump on the Connectivity Profile you can get the traffic unencrypted and see what traffic is coming over the tunnel:

 

#tcpdump -ni <connectivity profile name(like /Common/My_connectivity_profile)>:nnn -s0 host <Destination Server IP> or port 53 -vvv -w /shared/tmp/Connectivity_Profile.pcap

 

https://support.f5.com/csp/article/K411

 

You can also download and run the Client Troubleshooting Utility and generate a report from the PC:

 

K12444: Overview of the Client Troubleshooting Utility for Windows (CTU):

https://support.f5.com/csp/article/K12444

 

I would look at the FltRedirSrv.txt file for errors (this is the log file for the DNS Relay Proxy). Also take a look at the "F5 Network Access Diagnostic" section so you can see what F5 services are running.