Reducing DNS lookups

If you are running Content Gateway in transparent proxy mode, you can enable the Always Query Destination option to reduce the number of DNS lookups and improve response time. When enabled, the Always Query Destination option configures the proxy to always obtain the original destination IP address of incoming requests from the ARM. Content Gateway then uses that IP address to determine the origin server instead of doing a DNS lookup on the hostname of the request. Because the client already performed a DNS lookup, Content Gateway does not have to.

In version 7.8.2 and later, when Always Query Destination is enabled, the value defined for the variable proxy.config.arm.use_hostname_for_wisp_and_reporting determines whether IP address or hostname is captured for reporting purposes.


	Important It is recommended that you do not enable the Always Query Destination option if Content Gateway is running in both explicit and transparent proxy mode. In explicit proxy mode, the client does not perform a DNS lookup on the hostname of the origin server, so the proxy must perform a DNS lookup. Also, the category lookup is performed based on the IP address, which is not always as accurate as a URL-based lookup. In addition, do not enable the Always Query Destination option if you want domain names, rather than IP addresses, in Web Security transaction logs.

To enable Always Query Destination:

Open the records.config file in the Content Gateway config directory (/opt/WCG/config).

Edit the following variable:


Variable	Description
proxy.config.arm. always_query_dest	Set to 0 to disable the Always Query Destination option. Domain names are captured. Set to 1 to enable the Always Query Destination option. IP addresses are captured; domain names are not.

Save and close the file.

To apply the changes, run the following command from the Content Gateway bin directory:

content_line -x