You can extend a network using either of the Layer 2 concentrators.

Before you configure Layer 2 network extension, you must be certain that you have the prerequisites, as explained in, “Verify Layer 2 Installation Requirements”.

Use cases 3 through 7 in Minimum Requirements for Single Path Use Cases rely upon network extension. A Layer 2 concentrator is required to stretch your on-premises network to vCloud Air and enable seamless migration between the data center and the cloud. Suppose that you have an application and a database on separate virtual machines in your vCenter, and you migrate the application into the Cloud.

If you are using the default deployment configuration (single path), both migration traffic and extended network traffic are routed through the Cloud Gateway. WAN optimization (if installed) and intelligent routing, are applied to all workloads. See “Single Path”.

The migration path and the data path are separate in cases 6 and 7. As usual, the Cloud Gateway maintains the secure channel, which gets the benefits of WAN optimization. Typically you route communication traffic between virtual machines over the alternate path so migration workloads do not affect communication traffic.

Data traffic between virtual machines uses the data paths established by the Layer 2 concentrators. See “Separate Paths for Migration Traffic and Layer 2 Extension Traffic”.

Minimum Product Versions for Network Extensions

vSphere vCenter


vCloud Air Dedicated Cloud, vDC


licensed for up to 100 Mbps

Hybrid Cloud Manager Standard


~600–700 Mbps at 10–15 ms latency

Hybrid Cloud Manager Advanced

1 Management IP for Hybrid Cloud Manager

HT 3–4 Gbps at 1500 fps per network

Hybrid Cloud Manager Enterprise


Advanced Networking Services Standard or Advanced

+1 IP for Cloud Gateway (fleet)

2 sequential IP addresses for each Cloud Gateway

+1 IP for each alternate path L2C or HT L2C

+1 IP for each alternate path L2C or HT L2C

The remainder of this section summarizes how Layer 2 Concentrator configuration affects the network extension use cases.