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Virtualization is the new trend to modern lifestyle. Computer industry nowadays is rushing to provide higher level of satisfaction to customers by taking advantage of the enormous capabilities of hardware platforms.
Currently, electronic circuits and hardware components are designed to sustain a great amount of “load”. The key to success is to fully take control of the capabilities of the physical layer, and VMware has accomplished this task.Creating virtual machines on top of a single physical machine is a reality. The concept depends on virtualization, but the result of this is something real. Something you can see in action, and measure with a grade of customer satisfaction.
Two is always greater than one. Having two virtual machines on a single physical machine reduces hardware expenses, limits deployment time and provides, by its nature, isolation and protection from the underlying physical resources.
Imagine having two or three computers in a single package. This is the idea behind virtual machines. Each virtual machine is isolated from one another and provides the illusion of having dedicated physical hardware (RAM, CPU, Network Cards and so on).
VMware Workstation as well as VMware Server has the so-called hosted architecture, where the virtualization software is installed on the pre-existing host operating system and relies on this operating system for physical resource management and device support.
VMware ESX Server, on the other hand, is an example of hypervisor architecture where there is no pre-existing operating system installed. Hence the virtualization software is the one that provides driver support.
Is there such a thing as a Virtual Network Interface Card? And if so, then how does it work? Well, first off: there is a virtual NIC and here’s how it works: The virtualization software emulates a network interface card in VMware Workstation. The virtual NIC appears to the user as a normal PCI Ethernet controller along with its own MAC address. Amazing, isn’t it?
There are two possible ways of emulating the connection to the host:
During the installation of the VMware software, three virtual networks are created by default: Bridged, Host-Only and NAT. Pictured below, VMnet0 is used for the Bridged interconnection, VMnet1 for Host-Only and VMnet8 for a NAT network. VMnet8 is a Host-Only network as well, which also provides Network Address Translation functionality.
Assigning the virtual machine to a virtual network.
These three preconfigured networks are selected individually using the radio buttons. Seven more virtual networks can be installed by the user and can be selected through the custom button. The latter are defined as guest-only networks, meaning that only the virtual machines are connected over these networks and not the host.
By default, VMnet0 is automatically bridged to the first available physical network interface card. That is not a problem if the host uses only one NIC. In case more than one interface card is used, then it is wise to disable this automatic assignment using the Automatic Bridging tab of the virtual network editor as seen below.
Configuring Virtual Network Editor on the virtual machine.
Afterwards, manually choose the interface to bridge to the virtual network using the Host Virtual Network Mapping tab, as seen below.
Manual mapping of virtual networks.
For VMnet1 and VMnet8 networks, a virtual DHCP server is created which assigns IP addresses dynamically to the virtual machines when using Host-Only and NAT networks, respectively. Enabling or disabling DHCP service is performed via Virtual Network Editor as seen below.
Enable/Disable DHCP service.
The most frequently used type of virtual network is the Bridged Network. VMnet0 is the default bridged network created at the time of VMware installation. There is no restriction on the number of bridged networks to be created as long as there are available physical interface cards on the host machine (a single physical network can be bridged with a single virtual network), and the maximum number of virtual networks, which is ten has not been reached. To define new bridge networks simply follow the virtual network mapping directions as seen above (See: Manual mapping of vistual networks).
The bridged virtual network is considered an extension of the physical network. Packets addressed to and originated from this virtual network traverse without restriction through the software bridge interconnection. The IP address and MAC address of the virtual machine are visible to the entire LAN segment. As far as the assignment of IP address is concerned, this has to be configured manually from the “Local Area Connection Properties”. DHCP in bridged networks cannot be used and it is therefore disabled.
VMnet8 is considered to be a NAT network. It has no practical difference from Host-only networks such as VMnet1, except that there is a NAT service on the host system assigned to this network. The IP address of this virtual network cannot be forwarded to the outside networks; neither can it be addressed by foreign networks.
NAT service installed by the VMware software on the host is responsible for translating the VM’s IP address to the host’s IP address. This functionality provides extra security due to the fact that traffic from the internet (the outside world) cannot reach the virtual machine although the other way around works normally if the network path of the host system to the outside world is operating normally.
Configuration of the NAT service can be performed via the Edit button on the Virtual Network Editor as pictured below. NAT service can also be stopped or restarted from this window as well.
Configuring NAT service
Choosing the Edit button will present the NAT service settings window (see below) where the IP address of the gateway, port forwarding, various timeouts and DNS entries can be configured. The IP address of the gateway will be used by the virtual machine so that all packets are addressed to that gateway to be translated by the NAT service.
Configuring NAT service
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Tagged:hypervisor architecture, It Training News, Virtualization, Virtualization Training, VMnet0, VMnet8, VMware, VMware Bridged Network, VMware ESX Server, VMware NAT Configuration, VMware NAT Network, VMware Server, vmware training, VMware Workstation
