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[FAQ] Web Proxy Auto Discovery (WPAD)

Polycom Employee & Community Manager

[FAQ] Web Proxy Auto Discovery (WPAD)

Web Proxy Auto Discovery (WPAD)


  • The Web Proxy Auto-Discovery Protocol (WPAD) feature enables Polycom phones to locate the URL of a Proxy Auto-Configuration (PAC) file you configure. 

    You can configure WPAD using configuration parameters on your provisioning server, DHCP, or DNS-A protocol mechanism to discover the PAC file location. 

    Values you configure using parameters take precedence over DHCP and DNS-A. 

    Polycom phones support Basic, Digest, and NTLM Authentication mechanisms to authenticate with a proxy server. Microsoft recommends using Blue Coat proxy with this feature.

Note: If the proxies you configure in the PAC file or configuration file are either invalid or unreachable with a working fallback proxy, the time to register with Skype for Business is delayed and the responsiveness of features that support WPAD degrade.


  • The VVX UC Software 5.7.0 added this feature.
  • The Trio UC Software 5.7.1 added this to the Trio range.

Some screens to troubleshoot WPAD via the Web Interface  Diagnostics > Skype for Business Status > WPAD or Diagnostics > Web Proxy Auto Discovery (WPAD) Status




WPAD Enabled




Proxy connect failed with an incorrect password




WPAD DNS Settings




Later Software Versions for CCX or Trio


Access the Proxy via “Settings” -> “Network” -> “Web Proxy”





Manual Proxy Configuration:


Parameter Permitted Values  Change Causes Restart or Reboot  Example Values
feature.wpad.enabled    1 – Enable WPAD (Default Skype for Business) YES 1
  0 – Disable WPAD (Teams mode only) YES  
feature.wpad.curl  Enter the Proxy Auto-Configuration (PAC) file location.  YES https://server/wpad.pac
feature.wpad.proxy Configure the web proxy server address. If you configure this parameter with a proxy address, the VVX phones do not discover or fetch the PAC file even if you configure a PAC file location using feature.wpad.curl.  YES PROXY
feature.wpad.proxy.username Enter the user name to authenticate with the proxy server.  YES proxyuser
feature.wpad.proxy.password    Enter the password to authenticate with the proxy server. The credentials you can use depend on how authentication is enabled on the proxy server. You can use administrator or user credentials. If Skype for Business Active Directory in integrated with the proxy server, you do not need to configure user name or password credentials.  YES proxypass1234


Example configuration to specify a Proxy:


<proxy feature.wpad.proxy="PROXY" />

You can specify multiple proxies using this parameter by separated each with a semicolon the same
way you specify them in the PAC file. For example:



Example to point manually to a PAC file:




WPAD PAC File Location




It is important to set the Mime Type to application/x-ns-proxy-autoconfig




Working log from correctly set Mime type:


0820141836|curl |3|00|Connected to iistestserver.sbaierhome.lab ( port 80 (#0)
0820141836|curl |1|00|HEADER_OUT: GET /wpad.pac HTTP/1.1
0820141836|curl |1|00|HEADER_IN : HTTP/1.1 200 OK
0820141836|curl |1|00|HEADER_IN : Content-Type: application/x-ns-proxy-autoconfig
0820141836|curl |1|00|HEADER_IN : Last-Modified: Mon, 20 Aug 2018 13:12:08 GMT
0820141836|curl |1|00|HEADER_IN : Accept-Ranges: bytes
0820141836|curl |1|00|HEADER_IN : ETag: "74708668738d41:0"
0820141836|curl |1|00|HEADER_IN : Server: Microsoft-IIS/8.5
0820141836|curl |1|00|HEADER_IN : Date: Mon, 20 Aug 2018 13:18:36 GMT
0820141836|curl |1|00|HEADER_IN : Content-Length: 3043





Logs when Mime type is not set:


0820134231|curl |1|00|HEADER_OUT: GET /proxy%2Fwpad.dat HTTP/1.1
0820134231|curl |1|00|HEADER_IN : HTTP/1.1 404 Not Found
0820134231|curl |1|00|HEADER_IN : Date: Mon, 20 Aug 2018 12:42:32 GMT
0820134231|curl |1|00|HEADER_IN : Server: Apache/2.4.18 (Ubuntu)
0820134231|curl |1|00|HEADER_IN : Content-Length: 292
0820134231|curl |1|00|HEADER_IN : Content-Type: text/html; charset=iso-8859-1
0820134231|curl |1|00|HEADER_IN : 
0820134231|curl |0|00|DATA_IN   : Data of len 292 not displayed
0820134231|curl |3|00|Connection #0 to host left intact
0820134231|curl |3|00|Closing connection #0
0820134231|nisvc|4|00|m_RetVal[0] eReqRspID[1] csStrippedResponse[HTTP/1.1 404 Not Found
Date: Mon, 20 Aug 2018 12:42:32 GMT
Server: Apache/2.4.18 (Ubuntu)
Content-Length: 292
Content-Type: text/html; charset=iso-8859-1
<title>404 Not Found</title>
<h1>Not Found</h1>
<p>The requested URL /proxy/wpad.dat was not found on this server.</p>
<address>Apache/2.4.18 (Ubuntu) Server at Port 80</address>


Log Level needed for debugging:





DHCP Option 55 with suboption 252 enabled:


Create a new Scope Option 252 with a String Value containing the proposed URL





During signing into Skype for Business the Polycom Phone will send a DHCP INFORM requesting suboption 252 via option 55:




And a correctly setup DHCP Server will respond with a DHCP ACK containing the URL




Phone downloading dat file


004708.766|nisvc|2|00|DHCP 252 Opt Value:
****************************HTTP SEND**************************

004708.778|nisvc|2|00|HTTP SEND:: DestUrl(, HttpResCode(200), curlRetCode(0) retVal(0)

****************************HTTP SEND**************************

 Example PAC File:


function FindProxyForURL(url, host)
	if( url.substring(0, 5) == "http:" )
		return "PROXY; PROXY; DIRECT";
	else if( url.substring(0, 6) == "https:" )
		return "PROXY; PROXY; DIRECT";
	else if( url.substring(0, 4) == "ftp:" )
		return "PROXY; DIRECT";
		return "DIRECT";


A good site for PAC examples can be found => here <=


The title Polycom Employee & Community Manager is a community setting and does not reflect my role. I am just a simple volunteer in the community like everybody else. All posts and words are my own & do not represent the views of Employer.


Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge. If you need immediate and/or official assistance please open a service ticket through your proper support channels.
Please also ensure you always check the VoIP , Video Endpoint , Skype for Business , PSTN or RPM FAQ's
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