How to restrict article from certain knowledge bases in agent workspace search result

[Shubhanshu Guh1]

Hi All,
When we are in a Case record in Agent Workspace, we have requirement to restrict knowledge articles from certain knowledge bases. Say we have one Knowledge Base for external user so whenever an external user search for an article in related search result (highlighted)in the agent workspace, the related result should show articles present in external knowledge base not from internal knowledge base. Consider a user with snc_external role shouldn't get access to internal articles. 

Thanks!

[Shubhanshu Guh1]

hi
thanks for your reply but my query is related to Agent workspace's Related Search Result (contextual search) not to portal. 
when the user search for the article on portal, they get a access error related message.

Thanks.