VMware Server 2.0 DHCP Configuration

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In order for a client to connect to a TCP/IP based network, it needs a Internet Protocol (IP) address which uniquely identifies it among the other devices connected to the network. In addition, the addresses of one or more DNS servers and a gateway may optionally be configured. One way to configure this is to manually assign this information to each client on the network. Whilst this approach can work for small network, it quickly becomes unmanageable in larger enterprises. To alleviate this problem, the Dynamic Host Configuration Protocol was created. This takes the form of one or more servers on a network which dynamically allocate IP addresses and other network configuration information to network clients.

As outlined in the chapter entitled VMware Server Virtual Network Architecture, the VMware Server infrastructure includes a built-in Dynamic Host Control Protocol (DHCP) server for the purpose of assigning dynamic IP addresses, DNS and gateway information to virtual machines running in NAT and Host Only virtual networks. Virtual machines running on a bridged VMware Server virtual network must either have a static IP address assigned, or obtain one from a DHCP server running on the external network to which the bridge connects.

As with any other DHCP server, the one embedded into VMware Server provides a number of different configuration options. As such, this chapter will focus of configuring the VMware Server DHCP server on both Linux and Windows host operating systems.

Static and DHCP IP Address Allocation Ranges

When a NAT or HostOnly network is created it is assigned a Class C IP subnet address range (for example - In practice, VMware divides this address range and allocates specific addresses and address ranges for specific uses. These divisions differ between NAT and HostOnly virtual networks and are outlined in the following tables:

= HostOnly Virtual Network IP Addresses

<td> The IP address of the host machine. Provides a way for the virtual machines to communicate with the host. Example: </td> <tr bgcolor="#e9e9e6"> <td>subnet.2 - subnet.127</td> <td>Reserved for use as static addresses for virtual machines which are not configured to obtain an IP address from the VMware DHCP server. Example: -</td> </tr> <tr> <td> <p>subnet.128 - subnet.253</p> </td> <td> The pool of IP addresses available for dynamic allocation to virtual machines by the VMware DHCP server. Example: - </td> </tr> <tr bgcolor="#e9e9e6"> <td>subnet.254</td> <td>Used as the IP address of the VMware DHCP server.</td> </tr> <tr> <td> <p>subnet.255</p> </td> <td> The HostOnly virtual network broadcast address. </td> </tr> </table>

= NAT Virtual Network IP Addresses

Configuring the VMware Server DHCP Server on Windows Hosts

The built-in VMware DHCP server is configured on Windows host systems using the Virtual Network Editor tool, launched via the Start -> All Programs -> VMware -> VMware Server -> Manage Virtual Networks menu option. Once loaded, the DHCP settings are accessed by clicking on the DHCP tab as illustrated in the following figure:

Configuring the DHCP settings on a VMware Server Windows host

The screen displays a list of currently configured virtual networks for which the built-in DHCP server is available. In the above example this includes the vmnet1 (host only) and vmnet8 (NAT) virtual networks. Beneath the virtual network list is the DHCP service panel which lists the current status of the server and provides options to stop, start and restart the service.

To adjust the DHCP settings for a specific virtual network, simply select the network from the list and click the Properties button to display the DHCP settings dialog:

Configuring the DHCP settings for a specific virtual network

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