We have two farms. Farm B handles all indexing of content and has the query server. We have sites on Farm A, and we want all of their searches to be run on the query server in Farm B. How can we set this up? Is there something we can setup at the webapp or farm level?
I've never had to do this, but I believe the answer is to have an SSP that is shared by the 2 farms. Here is a technet article discussing inter-farm shared services: http://technet.microsoft.com/en-us/library/cc262179.aspx
And a blog post that talks specifically about having one farm control the search for another using inter-farm SSP: http://www.dotnetmafia.com/blogs/dotnettipoftheday/archive/2008/12/04/sharing-an-index-between-sharepoint-farms.aspx
Here are the basic steps I performed to share search accross two farms.
On the parent farm:
On the child farm