Unicast Traffic between VMs in VMware NSX-T environment

Unicast Traffic between VMs in VMware NSX-T environment

It is important to understand the unicast traffic between two virtual machines in a VMware NSX-T environment. 

For each segment/logical switch attached to the NSX virtual switch, a table of unicast MAC addresses are maintained. Frames forwarded to unicast MAC addresses are forwarded only to the corresponding port.

There are two ways to assign MAC addresses to virtual NICs (vNICs) of VMs: either locally or remotely (when the MAC address is associated with a remote TEP).

The MAC addresses of all known MAC addresses in Layer 2 are either available locally or directly through point-to-point tunnels in the overlay network. However, in NSX-T, the MAC address tables must be filled by the NSX-T Controller or by learning from the data plane.

Let's talk about the unicast traffic flow between the VMs ( VM1 and VM5)

Fig 1.1- Unicast Traffic in VMware NSX-T

How communicating between VM1 and VM5, Lets check below 

Upon receiving a frame from Virtual Machine (VM5) a lookup is performed in the MAC address table of “Hypervisor 5” for the destination MAC address. “Mac1” is associated to the “TEP1” on “Hypervisor 1”.

TEP1 looks for the destination MAC of the original frame and finds "Mac1", pointing to the vNIC of "VM1". "Hypervisor 5" encapsulates the frame and transfers it to "TEP1". "Hypervisor 1" receives the tunnel packet, addressed to itself, and decapsulates it.