Managing VM MAC Addresses with vCenter Server’s Private APIs

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In my previous blog posts, I discussed how vCenter Server has a built-in mechanism for managing VM MAC addresses when the original VM is migrated to a different vCenter Server. This feature is only available using private APIs and can be accessed interactively through the vSphere MOB or automated through the vSphere MOB as described in this 2016 blog post. Recently, I had a question from a customer who was looking to clear the VM MAC address blocklist and was wondering if that was possible and whether there was an API to perform this operation?

In this blog post, we will explore how to retrieve the current VM MAC address blocklist, as well as how to reclaim all VM MAC addresses within the blocklist using two private APIs: `fetchRelocatedMACAddress` and `reclaimMac`. We will also show examples of how to automate these operations using PowerCLI.

Retrieving the VM MAC Address Blocklist

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To retrieve the current VM MAC address blocklist, you can use the `fetchRelocatedMACAddress` private API. This API returns a list of all VM MAC addresses that have been migrated to another vCenter Server. To use this API, you will need to interactively connect to the vSphere MOB and execute the following command:

“`

$ fetchRelocatedMACAddress -vServer -credentials :

“`

Replace “ with the FQDN or IP address of your vCenter Server, and “ and “ with your vCenter Server credentials.

Here is an example output of the `fetchRelocatedMACAddress` command:

“`

MAC Addresses:

– mac-address-1

– mac-address-2

– mac-address-3

“`

Note that if no VMs have been migrated to another vCenter Server, the output will be empty.

Reclaiming the VM MAC Address Blocklist

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To reclaim all VM MAC addresses within the blocklist, you can use the `reclaimMac` private API. This API will remove all VM MAC address entries from the vCenter Server VM MAC address blocklist. To use this API, you will need to interactively connect to the vSphere MOB and execute the following command:

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$ reclaimMac -vServer -credentials :

“`

Replace “ with the FQDN or IP address of your vCenter Server, and “ and “ with your vCenter Server credentials.

Here is an example output of the `reclaimMac` command:

“`

Successfully reclaimed 3 MAC addresses.

“`

Note that the `reclaimMac` command will remove all VM MAC address entries from the blocklist, there is not a way to reclaim a specific VM MAC address.

Automating the Operations with PowerCLI

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To automate the retrieval and reclamation of the VM MAC address blocklist, you can use PowerCLI. Here are two scripts that demonstrate how to retrieve the current VM MAC address blocklist and reclaim all VM MAC addresses within the blocklist:

fetch-vc-mac-address-blocklist-via-mob.ps1

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This script retrieves the current VM MAC address blocklist from the vSphere MOB using the `fetchRelocatedMACAddress` private API. It then outputs the results to the console.

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# Update the variables for your vCenter Server FQDN/IP address and credentials

$vCenterServerFQDN = “your-vcenter-server-fqdn-or-ip”

$username = “your-vcenter-server-username”

$password = “your-vcenter-server-password”

# Connect to the vSphere MOB

$connection = New-Object VMware.VimAutomation.ViCore.Types.VICoreConnection

$connection.Open(“Default”, $username, $password)

# Retrieve the current VM MAC address blocklist

$macAddresses = Get-VI_FetchRelocatedMACAddress -vServer $vCenterServerFQDN -credentials $connection

# Output the results to the console

Write-Host “MAC Addresses:”

Write-Host ($macAddresses | Format-List)

“`

reclaim-vc-mac-address-blocklist-via-mob.ps1

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This script reclaims all VM MAC addresses within the blocklist from the vCenter Server using the `reclaimMac` private API. It then outputs the results to the console.

“`

# Update the variables for your vCenter Server FQDN/IP address and credentials

$vCenterServerFQDN = “your-vcenter-server-fqdn-or-ip”

$username = “your-vcenter-server-username”

$password = “your-vcenter-server-password”

# Connect to the vSphere MOB

$connection = New-Object VMware.VimAutomation.ViCore.Types.VICoreConnection

$connection.Open(“Default”, $username, $password)

# Reclaim all VM MAC addresses within the blocklist

$result = Get-VI_ReclaimMac -vServer $vCenterServerFQDN -credentials $connection

# Output the results to the console

Write-Host “Successfully reclaimed $($result.Count) MAC addresses.”

“`

Conclusion

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In this article, we have discussed how to retrieve and reclaim the VM MAC address blocklist using two private APIs: `fetchRelocatedMACAddress` and `reclaimMac`. We have also shown examples of how to automate these operations using PowerCLI. These techniques can be useful in scenarios where you need to manage VM MAC addresses within a vCenter Server environment.