Updated: January 18, 2010
VMware Server is a powerful, free virtualization software that you can use to run multiple instances of various operating systems in top of your desktop, each a separate entity running its own virtual environment. We've talked about this concept, as well as many other, more specific and detailed features, at great length in quite a few articles.
We've had some general advice on virtualization and we've discussed some tips and tricks on how to enhance VMware Server, but we've never really focused on the power of VMware Server networking stack, which is probably the most advanced and fully featured virtual router of any desktop virtualization product available. Until today, that is.
In this tutorial, I will show you how you can significantly enhance the control of your network setups when using VMware Server, including how to add new virtual adapters, how to bridge them to your real interfaces, how to setup new subnets, change DHCP and NAT settings, and more.
This is the utility that you need. In the VMware Server console, it is accessed from Host > Virtual Network Settings.
The Editor has a tabbed interface that lets you control different aspects of your virtual networks. The Summary tab, the one that opens by default, lists down the currently active networks and their status. By default, when you install VMware Server, you get three virtual devices installed:
VMnet0, which is automatically bridged to your default gateway; this allows you have network and Internet access without fussing with forwarding and firewall rules.
VMnet1, which is used for Host-only networking, quite similar to what we've seen in the VirtualBox network tutorial. This network adapter will be used only if you configure your guest machines to use Host-only type of network connections.
VMnet8, which is used for NAT - almost like your home router. Your hosts will have internal addresses that cannot be accessed outside the local network, but you will still be able to communicate with other local subnets on your grid.
The IP addresses chosen for these adapters will usually be arbitrary. What more, whenever you update your VMware Server, new IP addresses will be assigned, possibly messing up your setup. Not to worry, I will show you how you can control that.
This is the second tab. This tab tells you how the network communication will be routed. Most people need not touch this tab. Advanced users may want to manually override the settings and even exclude some network adapters from being accidentally used by VMware. This might be useful if you want to have separate virtual networks inside your LAN.
The third tab is very useful, but it does not exist alone. It is used in conjunction with the fourth tab, Host Virtual Adapters. We will soon learn exactly how and why.
In this sub-menu, you can configure the pairing between networks and adapters.
For example, you may want to bridge VMnet2 to one physical card, while VMnet3 will be bridged to another, physically separate from one another. Alternatively, you can create new virtual adapters and assign them their own networks, regardless of the actual physical topology.
This means you can have as many as eight bridged/Host-only/NAT networks, some of which are linked to real physical networks and others that exist only as virtual devices inside your operating system.
Change Subnet/DHCP/NAT settings
Earlier we mentioned the fact that VMware Server pretty much randomly chooses the subnets for its adapters. Between two updates, you may end up running your machines on completely new segments. If you have virtual machines that must use static IP addresses or are shared by several hosts running VMware Server, you may have problems with this.
Luckily, you have full control over your virtual adapters. Click on the > arrow for any existing adapter and then edit the relevant section.
Here, you can change your network settings. For example, you can use 192.168.x.x or maybe 10.x.x.x, just make sure to set the Subnet Mask accordingly. This step necessitates that you be slightly familiar with networking concepts, like CIDR, but it should not be too difficult.
For example, Subnet Mask 255.255.255.0 is also known as /24 class, which allows 256 IP addresses in your network, including the gateway, which is .0 and .255, which is the broadcast. You can change that, for example, use /29, which lets you have only eight hosts in your network, but this may be what you want. In that case, your Subnet Mask will be 255.255.255.248.
For example, you may want to change the start and end IPs and the max. lease time. Some of the options may not be available for change in this menu, but you can control them via Subnet, like we did before.
Assuming you went with the /29 example, then your start and end IP addresses would cover a much smaller range. Likewise, the broadcast address would probably not be .255, but something else.
To make a practical example, let's say you licked 192.168.144.0 as your network. Then, you may want to use 192.168.144.1 as the start address for your eight-host network, 192.168.144.6 as your end address, 192.168.144.7 would be the broadcast.
Similarly, you can govern NAT settings, including port forwarding and DNS options, FTP connection mode, as well as Netbios on Windows. Not really necessary on modern operating systems.
Under this tab, you can setup new adapters and remove existing ones.
Click on Add to configure a new one:
After it has been set, go to Host Virtual Network Mapping tab and set the desired network range, including Subnet, DHCP and NAT settings, and optionally bridge it to other devices on your machine.
In a way, this tab is slightly redundant, as it does some of the tasks seen on previous tabs. Again, you can add new adapters. However, most importantly, you can start, stop or restart the DHCP services on selected adapters. You may want to do this in case your clients won't let go of their leases or you need the DHCP service to reread its configuration, following a change in the physical topology.
Similarly, you can control the NAT service. Might be needed if you have clients running, forcing them to renew their connections and obtain new IP addresses.
And that's it! Now you know everything about VMware Server powerful networking!
No more fear using the seemingly complicated VMware Server network stack. It's actually very simple and friendly, you just need to take it easy and pay attention to the many functions and options.
You now know how to add and remove virtual adapters, bridge them to physical devices, restart DHCP and NAT services, change the IP address and Subnet Mask of any one of your adapters, and other cool things. From now on, you'll have more fine-grained control and better understanding of your setup when working with VMware Server. Virtualization is great fun and has now become even greater.
I hope you've liked this tutorial. See you around!