Summary: In some cases it is necessary to explicitly set the IP address for a host name the search appliance crawls or contacts. For example, you would like the host name test.google.com to resolve to the IP address 192.168.0.1, so when the appliance crawled http://test.google.com it would go to the IP address 192.168.0.1, regardless of what the DNS server returned.
Fix: You need to create mapping between specific hostname and an IP address. Use the Administration > DNS Override page to do that. Host names that you enter by using this page will be resolved internally to the corresponding IP address for all Google Search Appliance acitivities.
Additional Information: Help Center