limit HCX bandwidth in Azure VMware Solution

Question

Hi,

Is it possible to throttle or limit HCX bandwidth in Azure VMware Solution (AVS) Gen2?

Regards

Pravesh

Answer 1

Hello Pravesh,

In Azure VMware Solution (Gen2), there is no AVS‑specific setting that allows you to directly throttle or apply a hard bandwidth rate limit to VMware HCX traffic.

HCX in AVS runs as an integrated add-on and is configured through the HCX Cloud Manager in AVS and the HCX Connector on the source side. Bandwidth control, if available, is part of the HCX product itself rather than an AVS platform control. From an AVS platform perspective, there is no native option to enforce a strict HCX bandwidth cap.

If the goal is to prevent HCX migrations from consuming excessive WAN bandwidth during active migrations, the supported and common approach is to control this at the connectivity and design level rather than trying to enforce a throttle inside AVS:

• Customers typically size and design the on‑premises‑to‑AVS connectivity path based on expected migration load. This often includes using dedicated connectivity (for example, a separate ExpressRoute circuit) when predictable and isolated throughput is required for migrations.
• HCX is supported over both ExpressRoute and VPN connectivity, provided the underlying network meets HCX underlay requirements. The effective throughput is governed by the characteristics and capacity of the chosen connectivity path.

If the concern is around migration performance and impact rather than enforcing a strict rate limit, there are platform‑level optimization options that help distribute load during heavy migration activity. In real‑world deployments, customers use techniques such as distributing network extension traffic across additional gateways, using multiple HCX Network Extension appliances, and spreading workloads to avoid hitting data path bottlenecks. These approaches help manage behavior under high migration load but do not act as explicit bandwidth throttles.

If a strict hard rate limit is required for business or operational reasons, that control is typically implemented on customer‑managed networking devices in the traffic path (for example, on‑premises edge devices or WAN equipment). Azure VMware Solution does not provide an AVS‑side mechanism to enforce a hard bandwidth cap specifically for HCX traffic. Any such enforcement should be carefully validated in your environment.

References:

• https://learn.microsoft.com/en-us/azure/azure-vmware/install-vmware-hcx
• https://learn.microsoft.com/en-us/azure/azure-vmware/configure-vmware-hcx
• https://learn.microsoft.com/en-us/azure/azure-vmware/azure-vmware-solution-nsx-scale-and-performance-recommendations-for-vmware-hcx
• https://learn.microsoft.com/en-us/azure/cloud-adoption-framework/scenarios/azure-vmware/on-premises-connectivity
• https://learn.microsoft.com/en-us/azure/azure-vmware/faq

Answer 2

The provided information does not describe any supported method to directly throttle or limit VMware HCX bandwidth within Azure VMware Solution (AVS) Gen2.

The only bandwidth control mechanism in the context relates to Azure Site Recovery for VMware, where replication traffic can be throttled on the process server or influenced via registry keys on the Azure Backup/Recovery Services Agent. This applies to Site Recovery replication traffic, not HCX:

• Bandwidth can be throttled for VMware-to-Azure replication by configuring throttling in the Azure Backup MMC snap-in on the process server.
• Upload/download concurrency can be influenced via the UploadThreadsPerVM and DownloadThreadsPerVM registry values under HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Azure Backup\Replication.

No equivalent HCX-specific bandwidth throttling or QoS controls for AVS Gen2 are documented in the supplied material.

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References:

• Plan capacity and scaling for VMware disaster recovery to Azure