It will generate a **Proxy-Authenticate** header field containing a digest challenge (and not <del>Proxy-Authorize</del> header field as written in the manual page)

The header field looks like this:
Proxy-Authenticate: Digest realm="192.168.1.15", nonce="462c7effba07312005e1116c8236295cad5c0c84"

The challenge is sent in a 407 (Proxy Authentication Required) reply message.

[Emin Gabrielyan, 070424]