Configuring DCOM (Distributed COM) to Connect an OPC client to an OPC Server in multiple Domains.   Domain Trust Relationship Considerations DCOM Tutorial Home When you're going from one domain to another and browsing OPC servers, probably the biggest issue to be concerned with is domain trust relationships. When you have multiple domains, there are setups in BOTH domains that must be made so that Domain A trusts users from Domain B and vice versa.  For DCOM to work properly you'd have to have the trust going both ways because there are DCOM calls going both ways and the security model will try and validate the security credentials of the user going both ways. It is beyond the scope of our free support to show users how to setup Domain Trusts, but the good news is any decent network administration book will address the issue.  Having said that, with Domain trusts setup properly, then you still have to have the Dcom permissions setup properly as we discuss in our Dcom Configuration appnote. Warning: contents of this tutorial are Copyright Software Toolbox, Inc. 2001-2002, and may not be reproduced in electronic or written form without written permission of Software Toolbox Inc. Anyone found copying copyrighted material from this site for use on another site will be prosecuted. You are welcome to link to this site from your site. The information in this article is accurate to the best of our professional judgement at the time of writing but is subject to change.