Part 2: VMware NSX-T Replication Modes

VMware NSX-T Replication Modes

Here in this article, we will talk about VMware NSX-T replication mode as earlier we talked replication mode in NSX environment.

As we discuss in our earlier article, VMware NSX-T has 2 replication modes and these are Head end replication and Two tier replication.

Head End Replication:
The head end replication procedure ensures that every time a VM in the hosts sends the BUM traffic it is also sent to all the target TEPs which are intended to receive it. 

This utilizes the resources (processing power, etc.) of Source TEPs for sending packets to the target TEPs.

The level of traffic over the physical network increases with this mode since every time it needs to be initiated by the Source TEP

Two Tier Replication
The workload is distributed in a Two Tier Hierarchical fashion, in which BUM traffic is sent across to all intended hosts (which have the same overlay segment VMs as the source TEP) in the same TEP subnet. For hosts in different TEP subnets, only one copy of packet (unicast) is sent to designated hosts.

It is then the responsibility of this designated host to replicate BUM packets to other intended hosts in that TEP subnet.

We cannot achieve Two Tier Replication benefits if all TEPs are in the same subnets across the different racks as the Source TEP is also responsible for sending BUM packets across all intended TEP hosts.

In order to achieve better scalability and benefits from this replication mode, different TEP subnets should be used.