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VMware Server 2.0 DHCP Configuration

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<table border="0" cellspacing="0" width="100%"><tr><td width="20%">[[VMware Server NAT Configuration|Previous]]<td align="center">[[VMware Server 2.0 Essentials|Table of Contents]]<td width="20%" align="right">[[Managing VMware Server 2.0 Virtual Disks|Next]]</td><tr><td width="20%">VMware Server NAT Configuration<td align="center"><td width="20%" align="right">Managing VMware Server 2.0 Virtual Disks</td></table><hr>  <htmlet>vmware</htmlet>  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 a 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 on configuring the VMware Server DHCP server on both Linux and Windows host operating systems.
== Static and DHCP IP Address Allocation Ranges ==
<tr bgcolor="#cccccc" style="color:black" valign="top">
<th>
<p>IP Range</p>
</th>
<th>
<p>Description</p>
</th>
</tr>
 
<tr>
<td>
<p>''subnet''.1</p>
</td>
<td>
</td>
</tr>
 
<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: 192.168.33.2 - 192.168.33.127</td>
</tr>
 
<tr>
<td>
<p>''subnet''.128 - ''subnet''.253</p>
</td>
<td>
<tr>
<td>
<p>''subnet''.255</p>
</td>
<td>
<tr bgcolor="#cccccc" style="color:black" valign="top">
<th>
<p>IP Range</p>
</th>
<th>
<p>Description</p>
</th>
</tr>
<tr>
<td>
<p>''subnet''.1</p>
</td>
<td>
<tr bgcolor="#e9e9e6">
<td>
<p>''subnet''.128 - ''subnet''.253</p>
</td>
<td>
<tr bgcolor="#e9e9e6">
<td>
<p>''subnet''.255</p>
</td>
<td>
The range of the IP address pool (essential essentially the range of addresses from which the DHCP server can allocate addresses to clients) may be altered by changing start ''Start IP address'' and end ''End IP address '' fields.
Also available for configuration are the lease values. A lease time is the duration for which an IP address is assigned to the same network client before it is returned to the pool for future use by another client. The lease time may be anything from a few minutes up to thousands of days. The optimal lease value depends on the network. If the virtual network environment is one in which virtual machines are frequently created and destroyed it is better to have a shorter lease time to prevent the pool of available IP addresses being exhausted. The reason for this being that the DHCP server will reserve IP addresses long beyond the life expectancy of the virtual machines to which they are assigned, thereby limiting the pool of available addresses for new virtual machines. For more virtual networks with a low turnover of virtual machines, longer lease times are often preferred, allowing each virtual machine to retain the same IP address for as long as possible.
== Configuring the VMware Server DHCP Server on Linux Hosts ==
The built-in DHCP server is configured on Linux host systems by manually editing the DHCP configuration files. There is one DHCP configuration file for each HostOnly or NAT virtual network. These files can be found in:
/etc/vmware/vmnet''n''/dhcpd/dhcpd.conf
where ''n'' represents the number of the virtual network, for example ''/etc/vmware/vmnet1/dhcpd/dhcpd.conf''. A typical dhcp.conf file will read as follows when viewing viewed in a suitable text editor:
<pre>
The file conforms to the standard dhcpd.conf file, and extensive details can be obtain via the Linux dhcpd.conf ''man'' page. The default settings are as follows:
* '''allow unkown-clients''' - Controls whether the DHCP server is permitted to assign IP addresses to clinets clients which do not have a host declaration.
* '''default-lease-time''' - The length of lease (in seconds) associated with an IP address when the requesting client does not specify a required lease time.
* '''max-lease-time''' - The maximum permitted lease time, in seconds, allowed for an IP address by the DHCP server. A request for a greater lease length by a client will be fulfilled at using the max-lease-time value.
* '''subnet / netmask'''' - The Class C subnet and netmask for the HostOnly or NAT virtual network to which the DHCP server is assigned.
* '''range''' - The range of addresses which constitute the pool from which IP addresses may be dynamically allocated to clients by the DHCP server.
* '''option domain-name''' - The optional name of the network domain. For example, ''techotopia.com''.
 
 
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