Vmware mac address of adapter is within the reserved address range

In some cases, however, you might want to reduce the number of gratuitous ARP packets. For example, if your cluster has a large number of VLAN interfaces and virtual domains and because gratuitous ARP packets are broadcast, sending a higher number gratuitous ARP packets may generate a lot of network traffic. As long as the cluster still fails over successfully, you could reduce the number of gratuitous ARP packets that are sent to reduce the amount of traffic produced after a failover. If failover is taking longer that expected, you may be able to reduce the failover time by increasing the number gratuitous ARP packets sent.

You can also use the following command to change the time interval in seconds between gratuitous ARP packets. For example, enter the following command to change the time between ARP packets to 3 seconds:. The time interval can be in the range of 1 to 20 seconds. The default is 8 seconds between gratuitous ARP packets. Normally you would not need to change the time interval. However, you could decrease the time to be able send more packets in less time if your cluster takes a long time to failover.

There may also be a number of reasons to set the interval higher.

OTM Tips and Tricks: Fixing Duplicate MAC Address error on VMWARE

For example, if your cluster has a large number of VLAN interfaces and virtual domains and because gratuitous ARP packets are broadcast, sending gratuitous ARP packets may generate a lot of network traffic. As long as the cluster still fails over successfully you could increase the interval to reduce the amount of traffic produced after a failover.

In most cases you would want to send gratuitous ARP packets because its a reliable way for the cluster to notify the network to send traffic to the new primary unit. However, in some cases, sending gratuitous ARP packets may be less optimal. If the FDB has a large number of addresses it may take extra time to send all the packets and the sudden burst of traffic could disrupt the network.

If you choose to disable sending gratuitous ARP packets you must first enable the link-failed-signal setting. The cluster must have some way of informing attached network devices that a failover has occurred. For more information about the link-failed-signal setting, see Updating MAC forwarding tables when a link failover occurs.

If virtual domains are not enabled, HA sets the virtual cluster to 1 and by default all interfaces are in the root virtual domain. Including virtual cluster and virtual domain factors in the virtual MAC address formula means that the same formula can be used whether or not virtual domains and virtual clustering is enabled.

Interfaces are numbered from 0 to x where x is the number of interfaces. Interfaces are numbered according to their has map order. See Interface index and display order.

How often do you need to configure virtual machine MAC addresses?

The first interface has an index of 0. The second interface in the list has an index of 1 and so on. VirtualBox provides multiple network modes for virtual machines. Each VirtualBox VM can use up to eight virtual network adapters, each of which in turn is referred to as a network interface controller NIC.

All virtual network adapters up to 8 can be configured with the VBoxManage modifyvm command. VBoxManage is a command line management tool of VirtualBox that can be used for configuring all VirtualBox settings including VirtualBox network settings. VirtualBox network adapter settings can be accessed in the virtual machine settings select your VM, hit Settings and go to the Network section in the VM settings window.


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There you should see four adapter tabs. One virtual network adapter is enabled by default after virtual machine creation.

How to Changed MAC address of VM

A virtual network adapter is a software-emulated physical device. There are six virtual adapter types that can be virtualized by VirtualBox.

The industry standard virtIO networking drivers are supported by VirtualBox. These drivers are available for Linux with kernel 2.

Before We Begin

VirtualBox provides limited support for jumbo frames Ethernet frames that can carry packets which size is more than 1, bytes. If you need to use jumbo frames, select an Intel virtualized network adapter, and configure that adapter to work in bridged mode. If you try to enable jumbo frames for AMD-based virtual network adapters, jumbo frames will be dropped silently for input and output traffic.

Jumbo frames are disabled by default. VirtualBox provides a long list of network modes, which is one of the most interesting features of VirtualBox network settings.

Using VM Workstation for Advanced Networking

Each virtual network adapter can be separately configured to operate in a different network mode. For example, you can set the NAT mode for the adapter 1 and the Host-only mode for the adapter 2. You can select the network mode in the Attached to drop-down menu. A virtual network adapter is installed in a VM, but the network connection is missing, much like when you unplug the Ethernet network cable when using a physical network adapter.

This mode can be useful for testing. For example, you can enable this network mode for a short time to emulate unplugging the cable. When you disable the Not Attached mode by switching to another network mode, the network connection becomes available again. You can also check whether a DHCP client obtains the IP address correctly, whether the appropriate application can resume downloading after link interruption or packet loss, and so on.

Instead of using the Not Attached network mode, you can use any other network mode without ticking the Cable Connected checkbox. This network mode is enabled for a virtual network adapter by default. External networks, including the internet, are accessible from a guest OS.


  • How to force VMware to generate a new MAC address for a virtual machine;
  • Network Load Balancing for CAS.
  • OTM Tips and Tricks: Fixing Duplicate MAC Address error on VMWARE;

A guest machine is not accessible from a host machine, or from other machines in the network when the NAT mode is used for VirtualBox networking. This default network mode is sufficient for users who wish to use a VM just for internet access, for example. A virtual NAT device uses the physical network adapter of the VirtualBox host as an external network interface. The network mask is The default gateway for each VM is Port forwarding can be configured right from the VirtualBox VM network settings window by clicking the Port forwarding button seen in the screenshot above.

Detailed information about configuring port forwarding in VirtualBox network settings, which you can find below after the Network Modes section. This mode is similar to the NAT mode that you use for configuring a router. If you use the NAT Network mode for multiple virtual machines, they can communicate with each other via the network.

The VMs can access other hosts in the physical network and can access external networks including the internet. Any machine from external networks as well as those from a physical network to which the host machine is connected cannot access the VMs configured to use the NAT Network mode similarly to when you configure a router for internet access from your home network.

You cannot access the guest machine from the host machine when using the NAT Network mode unless you are configuring port forwarding in global VirtualBox network settings. The default gateway IP is Port forwarding is one more option that can be accessed and configured from this window. Port forwarding can be used to configure access from the host machine and other hosts of the same physical network to the services running on the guest OS inside the VM see details below.

See details about configuring port forwarding below in the Port Forwarding section. This mode is used for connecting the virtual network adapter of a VM to a physical network to which a physical network adapter of the VirtualBox host machine is connected. The actual fun begins, and like most fun things in life, it takes place in a text editor. Find the host VMnet8 section. Note the comment delimiters lines beginning with. Fill in the MAC address of the machine you saved earlier and the address you want assigned to the machine within the allowed range. It can get to be a pain to remember and type in IP addresses over and over again, so I usually create entries for them in my hosts file, which lets you map an IP to a host name.

For example, I might map webserver. There are a few examples already in the file, but the format is simple, with each line including an IP address, whitespace, and then the hostname.