Robert's Virtual

Building a Virtual Network - Part II

VMWare Server 2.0 networking

In this section we take a look at our virtual NIC choices and talk about their relation vis-à-vis  virtual networking. Knowing which NIC(s) type(s) to use in your VM's is essential to building the network and effectively making use of virtual machines.

When you install a NIC to your VM, you have a choice of three.

  • NAT - Configures your virtual machine to share the IP and MAC addresses of the host. The virtual machine shares the host’s public network identity, and has a private identity that is not visible beyond the host. NAT can be useful when you are allowed a single IP address or MAC address by your network administrator. You might also use NAT to configure separate virtual machines for handling HTTP and FTP requests, with both virtual machines running off the same IP address or domain. NAT works with Ethernet, DSL, and legacy phone modems.
  • Bridged - Configures your virtual machine as a unique identity on the network, separate from and unrelated to its host. In other words, it appears as a separate physical machine on the network even though it's making use of the host's NIC. Other computers on the network can communicate directly with the virtual machine and it can be configured with a static or a DHCP assigned address. Bridged networking works with Ethernet, DSL, cable, wireless, and legacy phone modems.
  • Host-Only - Configures your virtual machine to allow network access only to a private network existing entirely within the host. With host-only networking, the virtual machine can communicate only with the host and other virtual machines in the host-only network. This can be useful when you want a secure virtual machine that is connected to the host network, but available only through the host machine. In this configuration, the virtual machine cannot connect to the LAN or Internet.

VMWare supports each of these NIC types by making use of a virtual switch that supports the NIC type. So, when you select a NIC type, it is automatically connected to a virtual switch that supports that network type. NAT uses the VMnet8 switch, bridged uses VMnet0 and host-only uses VMnet1. Additionally, both NAT and Host-Only networks have a built-in DHCP server that assigns IP addresses to VM's, however the DHCP servers can be disabled.

virtual NICs
Virtual NIC's
virtal switches
Virtual switches
Host-Only (VMnet1) IP Address Distribution - Network Subnet Mask
RangePurpose to host machine - 127Static IPs - 253DHCP scope to DHCP server Broadcast
NAT (VMnet8) IP Address Distribution - Network Subnet Mask
RangePurpose to host machine to NAT device - 127Static IPs -253DHCP scope to DHCP server Broadcast

Virtual networks are managed through the Virtual Network Editor (Available from the Start Menu) and is preconfigured with the two virtual NICs discussed earlier plus the Bridged adapter (No DHCP Server attached). If you're running Vista you must run as administrator if you want to make any changes; that is, if UAC is enabled.

VMnet1 VMnet8 DHCP scope
Virtual network editor
Virtual network switches
VMnet0 thru 9

VMWare installs a total of ten virtual switches (VMnet0-9). As we've discussed, we have the three networks discussed earlier. The other seven are left unconfigured and each can be used as either a bridged or host-only NIC's, permitting you to build complex and /or separate virtual configurations.
Complex virtual network
Complex virtual network

This concludes Lab II. Next, we take what we've discovered up to this point and build our virtual network.

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