One of the best study guides around: VCIX-NV Study Guide | Lostdomain.org

It hasn't been updated for Cross-vCenter NSX yet but those operations are very similar to a singular environment, so studying up for the difference is not too hard.

Another good source of information in general but not directly mapped to the exam objectives (but it does cover Cross-vCenter NSX): https://www.packtpub.com/virtualization-and-cloud/learning-vmware-nsx

Hi fescaros

This study guide also cover for vcap6-nv deploy as well.

Thanks

This blog is a good reference: https://vzealand.com/2016/11/09/vcap6-nv-3v0-643-study-guide-exam-objective-reference-guide/