Load Balancing in NSX-T

Load Balancing in NSX T

Reference:

NSX T 2.5 Installation Guide

NSX T 2.5 Admin Guide

This post covers the configuration required to use load balancer which is a native feature in NSX-T.

Pre requisites before configuring load balancer:

1. NSX T Manager Cluster should be deployed

2. Transport zones should be defined.

3. Uplink profiles should be created.

4. Hosts should be configured as Host Transport Nodes.

5. Edge Transport Nodes should be deployed and configured.

6. Edge Cluster should be created.

7. Tier 0 Gateway should be created and peering with physical network should be in place.

Logical Topology for Load Balancing

As shown in the above topology, one Tier 0 Gateway aggregates the connections from two Tier 1 Gateways.
There is one Tier 1 Gateway dedicated for load balancing service.
The other Tier 1 Gateway is where the workloads are connected via segments.
Tier 1 Logical Router 2 is a DR only Logical Router/Gateway to which workload segment is connected.

Tier 0 Gateway peers with the physical network and hence always requires edge cluster.
In this lab, we will use the same edge cluster for Tier 0 Gateway and for the Tier 1 Gateway used for load balancing service.

If sufficient resources exist, then dedicated resources can be provided for load balancing service and as such a separate edge cluster can be created which will be used only for services viz. load balancing.

As shown above, this Tier 1 Gateway is a DR only Tier 1 Gateway.
Segments for workloads are connected to this Tier 1 Gateway.
This Tier 1 Gateway is not associated with any edge cluster.

The DR only status of Tier 1 Gateway can also be verified using the below command on CLI of the edge node.

The above Tier 1 Gateway is used for load balancing purpose.
Load balancing service requires presence of edge cluster.
As you can see, edge cluster is associated with this Tier 1 Gateway.
Also note that from route advertisement perspective, we are advertising LB VIP routes and LB SNAT IP Routes from this Tier 1 Gateway.

Communication between Virtual Server and the servers

The above diagram shows the communication between LB Virtual Server IP address 172.16.40.6 and the back end servers.
LB Virtual Server IP 172.16.40.6 is also used as SNAT IP address because the load balancer is in one arm mode. One arm mode of load balancer requires SNAT because the back end servers will then respond back to the SNAT IP.

Configuration of Load Balancer:

Here we are going to configure Layer 4 TCP based load balancing.

Server pool is defined as follows.

As shown above, server pool is created.
Please note that SNAT configuration has been applied while creating the server pool and the SNAT IP has been kept as the virtual server IP 172.16.40.6

Server pool members are configured.

Next, create a load balancer and associate Tier 1 Gateway ‘T1-LB’ with this load balancer.