Search across multiple site collections

hi -

i have three site collections, each with its own content database (http://servername/collection1,http://servername/collection2,http://servername/collection3)

When I search from collection2, I only get results from this collection and not the others.   How can I view results from all site collections?    The search settings are set to use contextual scopes (which includes all sites).    Am I missing a step somewhere?