About NX-OSv 9000
The NX-OSv 9000 is a virtual platform that is designed to simulate the control plane aspects of a network element running Cisco Nexus 9000 software. The NX-OSv 9000 shares the same software image running on Cisco Nexus 9000 hardware platform although no specific hardware emulation is implemented. When the software runs as a virtual machine, line card (LC) ASIC provisioning or any interaction from the control plane to hardware ASIC is handled by the NX-OSv 9000 software data plane.
VXLAN is an acronym for Virtual extensible Local Area Network. A joint venture by a few companies of which Cisco is one of them.VXLAN is yet another overlay solution which provides a solution to facilitate sending Layer-2 traffic over a Layer-3 network.
Also, one major reason for VXLAN [as per me at least] is due to the importance virtualization and cloud computing are gaining over the recent years. To isolate huge number customers in a cloud environment becomes extremely challenging when we have just 4,096 VLANs currently available to us [of which again, some cannot be used].
With the release of XE-3.13 VXLAN gets a much awaited unicast flavor. The configuration doesn’t change by much [except from the obvious that is there are no multicast configurations].
Multicast VXLAN, read up: https://iteachs.com/?post=110
A part from the addition of the unicast mode support for VXLAN, they have also changed the port-number. Initially the port was the same as that used by OTV, however, now that has changed.