APM Oauth client gives a HTTP 503 Service unavailable, DNS lookup failed error
I am trying to setup Azure AD as the Oauth server for the APM policy i have on the F5. When using the authorization grant flow and testing a VIP using the policy. I see that the user is redirected to Azure for the Authorization and comes back to the reply back URI( the same F5 VIP ) but the login prompt from azure is stuck at the "do you want to stay signed in page" and never comes back to the vip at /oauth/client/redirect. I see the debugger tool shows the response back with the auth code to the reply back URI but the status code is shown as failed instead of 302. After a while the bigip logout page pops up. The session logs show this error message
/Common/testazurexxxxx:Common:xxxxx:/Common/testazureADredirect_act_oauth_client_ag: OAuth Client: failed for server '/Common/Azurexxxx' using 'authorization_code' grant type (client_id=xxxxx-x-x-x-x-x-x-x), error: HTTP error 503, DNS lookup failed
I have added the DNS resolver as a abc.example.com and have it set to forward all dns traffic to the local dns server x.x.x.x on port 53. using . in the forward zone but the issue still remains. Let me know what might be causing this and what is the probable fix for this.