vSAN – MAC Learning Policy

In modern data centers, virtualization has become a popular way to optimize hardware resources and increase the flexibility of IT infrastructures. VMware vSAN is a storage technology that allows you to create a hyper-converged infrastructure (HCI) by combining storage and compute resources into a single software-defined platform. With vSAN, you can create a distributed storage architecture that provides high availability, scalability, and performance.

One of the critical components of vSAN is the MAC Learning Policy, which plays a crucial role in maintaining the health and performance of the storage network. In this blog, we’ll explore what MAC Learning Policy is and how it works.

What is MAC Learning Policy?

MAC Learning Policy is a feature of vSAN that allows the system to learn and store the Media Access Control (MAC) addresses of devices connected to the storage network. This feature helps the vSAN cluster to identify the location of virtual machines and maintain their connectivity when they migrate across the vSphere hosts.

In a vSAN cluster, each host has a network interface card (NIC) that is responsible for handling the network traffic. When a virtual machine is created, it is assigned a MAC address that is unique to the virtual machine. The vSAN cluster uses the MAC Learning Policy to learn the MAC address of each virtual machine and store it in a database.

How does MAC Learning Policy work?

MAC Learning Policy works by monitoring the network traffic between virtual machines and storing the MAC addresses of the devices that generate the traffic. The vSAN cluster uses a distributed database to store the MAC addresses, which is synchronized across all the hosts in the cluster.

When a virtual machine migrates from one host to another, the vSAN cluster uses the MAC address database to update the location of the virtual machine. This ensures that the network traffic is routed to the correct host and that the virtual machine maintains its connectivity.

MAC Learning Policy has several benefits, including:

1. Improved performance: By learning the MAC addresses of devices, the vSAN cluster can optimize the routing of network traffic, which can improve the performance of the storage network.
2. Increased flexibility: The MAC Learning Policy allows virtual machines to migrate across hosts without losing connectivity, which increases the flexibility of the infrastructure.
3. Enhanced scalability: The distributed database used by MAC Learning Policy allows the system to scale as the number of hosts and virtual machines in the cluster increases.

Impact of Not getting the MAC Learning Policy enabled

Note: This is one of the incident that I came across.

In the vSAN environment you will see DNS Lookup error:

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By Default thisparameter is set to “false”. But in the vSAN environment the setting should be set to “True”

• To list all vswitches, all VSS and VDS run the following command:

# netdbg vswitch instance list

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• To get the current state of the port run the following command:

# netdbg vswitch mac-learning port get -p 0 -dvs Test

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• To get the mac-learning enabled on the port run the following command:

# netdbg vswitch mac-learning port set -p 0 -dvs Test --enable

• To validate the settings run the following command:

# netdbg vswitch mac-table port get -p 0 -dvs Test

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The issue gets addressed post following the best practices.

Additional NSX-T Commands:

# nsxdp-cli vswitch mac-learning port get -p 0 -dvs Test

# nsxdp-cli vswitch mac-learning port set -p 0 -dvs Test --enable

Conclusion:

In summary, the MAC Learning Policy is a critical component of vSAN that helps maintain the health and performance of the storage network. By learning the MAC addresses of devices, the system can optimize the routing of network traffic, increase flexibility, and enhance scalability. As a result, the MAC Learning Policy is an essential feature for anyone using vSAN to create a hyper-converged infrastructure.