To be able to do this use component /atg/epub/deployment/TopologyManager/
You will find Primary Topology - the one is live now. Just press button "Download XML" for topology export.

Troubleshooting: if you will see security exception please enable /atg/dynamo/servlet/adminpipeline/AuthenticationServlet/ and login into dyn/admin
When you need to import Deployment Topology use:
Content Administration -> Admin console -> Configuration

Thanks