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NSE4 · Question #556

Which of the following statements are true when using Web Proxy Auto-discovery Protocol (WPAD) with the DHCP discovery method? (Choose two.)

The correct answer is C. The DHCP server provides the PAC file for download. D. If the DHCP method fails, browsers will try the DNS method.. When using WPAD with DHCP, the DHCP server provides the PAC file URL, and browsers will attempt DNS discovery as a fallback if the DHCP method fails.

Submitted by diego_uy· Apr 18, 2026Security Profiles and Content Inspection

Question

Which of the following statements are true when using Web Proxy Auto-discovery Protocol (WPAD) with the DHCP discovery method? (Choose two.)

Options

  • AThe browser sends a DHCPINFORM request to the DHCP server.
  • BThe browser will need to be preconfigured with the DHCP server's IP address.
  • CThe DHCP server provides the PAC file for download.
  • DIf the DHCP method fails, browsers will try the DNS method.

How the community answered

(15 responses)
  • A
    7% (1)
  • C
    93% (14)

Why each option

When using WPAD with DHCP, the DHCP server provides the PAC file URL, and browsers will attempt DNS discovery as a fallback if the DHCP method fails.

AThe browser sends a DHCPINFORM request to the DHCP server.

While DHCPINFORM is used for requesting configuration information, clients typically receive the PAC file URL via standard DHCP lease options during the initial lease request or a subsequent renewal, not a dedicated DHCPINFORM for WPAD discovery specifically.

BThe browser will need to be preconfigured with the DHCP server's IP address.

The browser does not need to be preconfigured with the DHCP server's IP address; it discovers the DHCP server automatically as part of the normal IP address acquisition process or uses existing DHCP information already obtained.

CThe DHCP server provides the PAC file for download.Correct

In the DHCP discovery method for WPAD, the DHCP server is configured with a specific option (commonly option 252) to provide the URL of the proxy auto-configuration (PAC) file to the client. The client then downloads the PAC file from this provided URL.

DIf the DHCP method fails, browsers will try the DNS method.Correct

Browsers typically implement WPAD with a robust fallback mechanism. If the DHCP discovery method (e.g., failing to receive option 252) does not yield a PAC file URL, the browser will then attempt to use the DNS discovery method (e.g., querying for 'wpad.domain.com') to locate the PAC file.

Concept tested: WPAD Discovery Methods (DHCP and DNS)

Source: https://docs.fortinet.com/document/fortigate/7.4.0/fortios-cookbook/241775/wpad-file

Topics

#WPAD#DHCP#Proxy Auto-discovery#PAC file

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