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VMware Server 2.0 DHCP Configuration

3,775 bytes added, 14:42, 21 October 2008
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[[Image:vmware_server_2_dhcp_network_settings.jpg|Configuring the DHCP settings for a specific virtual network]]
 
 
The range IP address pool (essential the range of addresses from which the DHCP server can allocate addresses to clients) may be altered by changing start and end 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.
 
The ''Default lease time'' is the lease time that will be used by the DHCP server if the network client does not specify a lease time when requesting an IP address from the DHCP server. The ''Max lease time'' is the maximum lease length permitted by the DHCP server, regardless of the lease requested by the client.
 
== 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 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 in suitable text editor:
 
<pre>
allow unknown-clients;
default-lease-time 1800; # 30 minutes
max-lease-time 7200; # 2 hours
 
subnet 192.168.103.0 netmask 255.255.255.0 {
range 192.168.103.128 192.168.103.254;
option broadcast-address 192.168.103.255;
option domain-name-servers ns1.techotopia.com, ns2.techotopia.com;
option domain-name "techotopia.com";
 
}
</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 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 broadcast-address''' - The TCP/IP broadcast address of the VMware virtual network.
 
* '''option domain-name-servers''' - The optional IP addresses or fully qualified domain name (FQDN) of name servers on the network. For example, ''ns1.virtuatopia.com''. Multiple servers must be comma separated.
 
* '''option domain-name'' - The optional name of the network domain. For example, ''techotopia.com''.
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