Major We are having proxy server authentication for accessing external sites in our System. When tried to validate the proxy server with credentials from "manage plugins" section and "advanced" tab in jenkins, we are getting "Failed to connect to http://www.google.com (code 407)" error.
But those proxy server and the credentials and absolutely correct as they work from other tools. And strangely sometimes validation works(once in a while) and most of the times not.
I had attached the error that we get from the Tomcat logs and the screen shot from Jenkins.
Please let me know if you need further details,
Please address this issue and resolve this, we are facing this since many days
Regards,
Vamsi Hari
[JENKINS-25870] Jenkins is not validating the proxy settings from "manage plugins" even though they are correct
I'm having the same issues.
I've tested with unauthenticated access to our proxy and it works fine that way. The same credentials i was trying can use things like curl and wget on the jenkins server.
Our proxy server can accept Basic, and NTLM type requests.
With a bit of testing it seemed like the username and password that is entered in this form is just dropped entirely from any requests that are sent through...?
Vinodhini Vijay
added a comment - I started Jenkins in Windows Service under my account and I no longer got the 407 error. The below solution worked for me for the 407 problem in Windows 7 machine.
1. Stop Jenkins from Windows Services
2. Goto Services.msc > Jenkins > Right Click > Properties > Logon > This account and type in your username and password
3. Click Apply and Ok
3. Start Jenkins
Vinodhini Vijay
added a comment - I started Jenkins in Windows Service under my account and I no longer got the 407 error. The below solution worked for me for the 407 problem in Windows 7 machine.
1. Stop Jenkins from Windows Services
2. Goto Services.msc > Jenkins > Right Click > Properties > Logon > This account and type in your username and password
3. Click Apply and Ok
3. Start Jenkins 
It appears as Jenkins does not support NTLM authentication at all. Maybe your proxy can be configured to support other authentication methods as a workaround.