Daz’s bits and bobs

When using wpad there are some things that you should take note of;

• DHCP wpad will override DNS wpad
• DHCP 252 option can in some cases be slightly slower to resolve than DNS – there may be a patch for WinInet to resolve this.
  
• You should always use lower case – wpad.dat  (it is case sensitive)
• DHCP will allow either a URL or a file location for wpad.dat

Within IE on the LAN settings tab if you have WPAD “automatically detect settings” enabled and also configure a proxy server the WPAD should override the manual proxy configuration.

There is some good detail at the usual places http://en.wikipedia.org/wiki/Web_Proxy_Autodiscovery_Protocol

I’ve done a bit of work around WPAD, but have yet to write up a decent “how-to”. I’ll update this the next time i dabble in the area.

Here is a quick example of the syntax of a typical wpad.dat file…

   function FindProxyForURL(url, host) {
      // our local URLs from the domains below example.com don't need a proxy:
      if (shExpMatch(url,"*.example.com/*"))                  {return "DIRECT";}
      if (shExpMatch(url, "*.example.com:*/*"))               {return "DIRECT";}

      // URLs within this network are accessed through 
      // port 8080 on fastproxy.example.com:
      if (isInNet(host, "10.0.0.0",  "255.255.248.0"))    {
         return "PROXY fastproxy.example.com:8080";
      }

      // All other requests go through port 8080 of proxy.example.com.
      // should that fail to respond, go directly to the WWW:
      return "PROXY proxy.example.com:8080; DIRECT";
   }

How to install DHCP and DNS on Fedora / Centos / Redhat box;

yum -y install dhcp.i386 bind.i386

Set services to auto start using ntsysv — services are called “dhcpd” and “named”.

How to configure dhcp;

nano /etc/dhcpd.conf — configure as per sample provided. The sample is usually located in the same directory.
service dhcpd restart – should start without problem if done correctly

Note: dhcp range has to be on the same network as your adapter. You can run dhcpd from the command line to diagnose any issues.

How to configure bind (DNS);

I usually just forward DNS requests to my internal router. To do this just edit /etc/resolve.conf and place the following line in the file;

nameserver 192.168.9.1

Use your ip above then all should be good. Test by pinging a domain like www.yahoo.com etc… You should get an ip back even if you don’t get successful pings (due to firewall etc). nslookup is also another quick and easy way to check DNS requests.