• Preetam Zare

Notes for Storage Guide 02

For Guide 01 click here

NetFlow is a network analysis tool that you can use to monitor network monitoring and virtual machine traffic.

NetFlow is available on vSphere distributed switch version 5.0.0 and later.

Switch discovery protocols allow vSphere administrators to determine which switch port is connected to a given vSphere standard switch or vSphere distributed switch.

vSphere 5.0 supports Cisco Discovery Protocol (CDP) and Link Layer Discovery Protocol (LLDP).

CDP is available for both vSphere standard switches and vSphere distributed switches connected to Cisco physical switches.

LLDP is only available for vSphere distributed switches version 5.0.0 and later.

When CDP or LLDP is enabled for a particular vSphere distributed switch or vSphere standard switch,

you can view properties of the peer physical switch such as device ID, software version, and timeout from the vSphere Client.

Enable Cisco Discovery Protocol on a vSphere Distributed Switch


1. Log in to the vSphere Client and select the Networking inventory view.

2. Right-click the vSphere distributed switch in the inventory pane, and select Edit Settings.

3. On the Properties tab, select Advanced.

4. Select Enabled from the Status drop-down menu.

5. Select Cisco Discovery Protocol from the Type drop-down menu.

6. Select the CDP mode from the Operation drop-down menu.

7. Click OK.

MAC Addresses

MAC addresses are generated for virtual network adapters that virtual machines and network services use.

In most cases, the generated MAC addresses are appropriate. However, you might need to set a MAC address

for a virtual network adapter, as in the following cases:

· Virtual network adapters on different physical hosts share the same subnet and are assigned the same

MAC address, causing a conflict.

· To ensure that a virtual network adapter always has the same MAC address.

To circumvent the limit of 256 virtual network adapters per physical machine and possible MAC address conflicts

between virtual machines, system administrators can manually assign MAC addresses.

By default, VMware uses the Organizationally Unique Identifier (OUI) 00:50:56 for manually generated

addresses, but all unique manually generated addresses are supported.

You can set the addresses by adding the following line to a virtual machine‘s configuration file:

ethernetnumber.address = 00:50:56:XX:YY:ZZ

where <number> refers to the number of the Ethernet adapter,

XX is a valid hexadecimal number between 00 and 3F (in decimal it is 63),

and YY and ZZ are valid hexadecimal numbers between 00 and FF(in decimal it is 255).

The value for XX must not be greater than 3F to avoid conflict with MAC addresses that are generated

by the VMware Workstation and VMware Server products.

The maximum value for a manually generated MAC address is:

ethernetnumber.address = 00:50:56:3F:FF:FF (in decimal 00:50:56:63:255:255)

You must also set the option in a virtual machine’s configuration file:


The first three bytes of the MAC address that is generated for each virtual network adapter consists of the OUI.

The MAC address-generation algorithm produces the other three bytes. The algorithm guarantees unique

MAC addresses within a machine and attempts to provide unique MAC addresses across machines.

The network adapters for each virtual machine on the same subnet should have unique MAC addresses.

Otherwise, they can behave unpredictably. The algorithm puts a limit on the number of running and suspended

virtual machines at any one time on any given host. It also does not handle all cases when virtual machines on

distinct physical machines share a subnet.

Who is responsible for generating MAC addresses in vSphere environment?

The VMware Universally Unique Identifier (UUID) generates MAC addresses that are checked for conflicts.

The generated MAC addresses are created by using three parts: the VMware OUI, the SMBIOS UUID for the physical ESXi machine, and a hash based on the name of the entity that the MAC address is being generated for.

When does MAC address changes?

After the MAC address has been generated, it does not change unless the virtual machine is moved to a different location, for example, to a different path on the same server. The MAC address in the configuration file of the virtual machine is saved.

All MAC addresses that have been assigned to network adapters of running and suspended virtual machines on a given physical machine are tracked. The MAC address of a powered off virtual machine is not checked against those of running or suspended virtual machines. It is possible that when a virtual machine is powered on again, it can acquire a different MAC address. This acquisition is caused by a conflict with a virtual machine that was powered on when this virtual machine was powered off.

For Guide 01 click here

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