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Sample Configuration - Network Load Balancing (NLB) UNICAST Mode Configuration

Setting up NLB UNICAST Mode:

Need two machines running Windows Server 2003 or later
Each machine needs to have at least one network card and at least one fixed IP address
Two adapters in each machine is recommended for best performance
One adaptor mapped to the real IP Address (Microsoft calls this the Dedicated IP) and one mapped to the ‘virtual’ IP Address (Microsoft calls this the Cluster IP)
One benefit of unicast mode is that it works out of the box with all routers and switches (since each network card only has one MAC address)
I n unicast mode, since all hosts in the cluster all have the same MAC and IP address, they do not have the ability to communicate with each other via their NLB network card
A second network card is required for communication between the servers

Note: Click the picture for a larger view.

To configure NLB UNICAST mode:

NLB Unicast Mode requires two NICs.
Add two virtual NICs to NLB configured virtual machines.
Use the Add New Hardware wizard to add new hardware to the virtual machine. The virtual hardware that you add appears in the hardware list displayed in the Virtual Machine Properties wizard. The selected guest operating system determines the devices that are available to be added to a given virtual machine.
Add an Ethernet adapter (NIC):
1. Start the Add Hardware wizard.
2. Select Ethernet Adapter, and click Next.
3. In the Network connection panel, choose either a named network with a specified label or a legacy network.
4. To connect the virtual NIC when the virtual machine is powered on, select Connect at power on.
5. To complete the wizard, click Finish.

Notes:

ESX vSwitch properties Notify Switches = NO
Unicast mode reassigns the station (MAC) address of the network adapter for which it is enabled and all cluster hosts are assigned the same MAC (media access control) address, you cannot have ESX send ARP or RARP to update the physical switch port with the actual MAC address of the NICs as this break the the unicast NLB communication
ESX vSwitch security properties must be set to default, Forged Transmits = Accept.

See the example screen shoots below:

Click the image for a larger view.

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