Web Proxy support from DHCP

  • 2953490
  • 21-Aug-1999
  • 27-Aug-1999
  • 1

Symptoms

Customer enquired whether we support Web Proxies in DHCP
( http://www.ietf.org/internet-drafts/draft-ietf-wrec-wpad-01.txt )

Solutions

To configure the DHCP server to support WPAD option:

- From dnsdhcp console (from nw5sp2), select "Global Preferences" on the "DHCP Service" tab.
- Select "DHCP Options Table".
- Click "Add" to define new DHCP option.
- Set the option code to 252.
- Set the data syntax to String (per section 4.4.1 of the draft-ietf-wrec-wpad-01.txt doc).
- Set the description to something like "Web Proxy Auto-Discovery".
- Click OK.

To set a Global DHCP Option value for WPAD:

- Select "Global DHCP Options" from "Global Prefs" and click "Modify".
- The "Modify DHCP Options" presents a list of available DHCP options which should now include Web Proxy Auto-Discovery, Code 252 -- select it and click "Add", at which point the option should appear in the list of Selected DHCP Options. Click on it in that list and you'll be prompted in the frame below titled "Web Proxy Auto-Discovery" to enter a value. Enter a string, e.g. http://server.domain/proxyconfig.pac

The DHCP server should now respond to option 252 with the curl, which can be confifgured on a per subnet basis if desired.

The dhcp3tab file should now look something like:

[Globals]
    Config Options = 00 00 00 00 FC 24 68 74 74 70 3A 2F 2F 73 65 72 76 65 \
        72 2E 64 6F 6D 61 69 6E 2F 70 72 6F 78 79 63 6F 6E 66 69 67 2E 70 61 63
    Subnet Attributes = \
        "166.70.104.64(rminc)"

[Subnet : "166.70.104.64(rminc)"]
    Subnet Address = 166.70.104.64
    Subnet Mask = 255.255.255.240
    Lease Time = 259200
    Config Options = 00 00 00 00 FC 21 68 74 74 70 3A 2F 2F 77 77 77 2E 6F \
        6E 63 61 6C 6C 64 62 61 2E 63 6F 6D 2F 66 72 65 64 2E 70 61 63
    Subnet Type = 0

Where the Config Options under [Globals] and [Subnet] are the two different strings entered,
with FC being the option number (252), the next octet being the length of the string, and then
the string itself. You'll recognise the "http://" pattern.