VMware NSX-T : N-VDS, teaming Policies and Uplink/pNIC

Today we are going to discuss about N-VDS, teaming policy in N-VDS and some about Uplink vs pNIC in N-VDS

Let's start with the N-VDS first. As many of you know that the primary component involved in the data plane of the transport nodes is the N-VDS. The NVDS forwards traffic between components running on the transport node (e.g., between virtual machines) or between internal components and the physical network. 

The N-VDS must own one or more physical interfaces (pNICs) on the transport node. 

The N-VDS is mandatory with NSX-T for both overlay and VLAN backed networking. On ESXi hypervisors, the N-VDS implementation is derived from VMware vSphere® Distributed Switch™ (VDS). 

With KVM hypervisors, the N-VDS implementation is derived from the Open vSwitch (OVS)

Teaming Policy in N-VDS
The teaming policy defines how the N-VDS uses its uplinks for redundancy and traffic load balancing. There are two main options for teaming policy configuration:

Fig 1.1- N-VDS teaming Policies

Failover Order: An active uplink is specified along with an optional list of standby uplinks. Should the active uplink fail, the next available uplink in the standby list takes its place immediately.

Load Balanced Source/Load Balance Source Mac Address : Traffic is distributed across a specified list of active uplinks. The “Load Balanced Source” flavor makes a 1:1 mapping between a virtual interface and an uplink of the host. 

Traffic sent by this interface will leave the host through this uplink only, and traffic destined to this virtual interface will necessarily enter the host via this uplink.

The “Load Balanced Source Mac Address” goes a little bit further in term of granularity for virtual interfaces that can source traffic from different mac addresses: two frames sent by the same virtual interface could be pinned to different host uplinks based on their source mac address. 

Uplink vs. pNIC in N-VDS
The N-VDS introduces a clean differentiation between the pNICs of the host and the uplinks of the N-VDS. 

Fig 1.2- Uplink and pNIC

The uplinks of the N-VDS are logical constructs that can be mapped to one or multiple pNIC bundled into a link aggregation group (LAG).