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MAC addresses and cloning VMs

The MAC addresses of virtual adapters are an important topic. They relate to a unique internal ID which VMware issues for each VM: the "Universally Unique Identifier" (UUID). After copying VMs, the VMware server asks whether it should issue a new UUID or keep the old one. When cloning VMs a new ID must be assigned, as otherwise several VMs would end up with the same MAC address.

If adapters are to receive static MAC addresses, for example because an application's license key depends on them, the admin can specify this directly in the VM's config file, but only within the tight limits of the MAC address space reserved for VMware.

The MAC addresses of physical cards can only be allocated within the guest. This may become necessary after adopting a physical machine (P2V), if license keys or authentications depend on the old MAC address - in Windows via the virtual adapter's network configuration; in Linux with the ifconfig ethX up hw ether 00:xx:xx:xx:xx:xx command.

Virtual networks offer more flexible configuration at the click of a few buttons without having to re-plug cables or install switches. Once the basic concepts have been understood, individual configurations can be established and used for test environments.

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