This is one of the core need for penetration tester to have upstream proxy configuration for burp suite. For example if you want test your application through a proxy on your penetration test environment  or if you need to test web proxy/url filter directly including proxy bypass test scenarios then having upstream proxy configuration will be very useful.

This configuration will allow burp suite forward all intercepted traffic to defined proxy server.

To configure upstream proxy;

1-Go user option
2-Click Upstream Proxy Settings “Add”
3-Define your proxy server settings as needed. It also support NTML authentication which is very useful for corporate infrastructure