Tech Notes

Configuring DHCP Servers to use the DHCP User Class Option

Technical Note 2210

Last Reviewed 11-May-2007
Applies to:
Mobility XE server version 7.1
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Summary

Mobility XE version 7.1 and higher supports using the DHCP user class option to assign Virtual IP addresses (VIPs) by user group, device class, user, and device. For example, a DHCP server can be configured to hand out one pool of VIPs to members of a particular Mobility user group, a different pool of VIPs to devices in a particular Mobility device class, and even individual addresses to individual users and devices. This technical note describes how to configure the Mobility Client setting "Virtual Address - DHCP User Class" and a DHCP server(s) to provide this functionality.

Configuration

Mobility Server setting

The Mobility XE Global Server Setting "Virtual Address - Allocation" must be set to Use DHCP to obtain IP addresses.

Mobility Client setting

The Mobility Client Setting "Virtual Address - DHCP User Class" must be configured at the appropriate level to allow user groups and/or device classes to pull their VIPs from a DHCP server. The examples below make use of a user group named "sales-group" and a device class named "MDT-devices".

Follow these steps to configure a user group named "sales-group" to obtain VIPs from a DHCP-assigned pool:

In the Mobility XE Server console, open the Client Settings page.
In the lefthand column, find the User Setting Overrides section and highlight the "sales-group" entry.
In the middle section, highlight the "Virtual Address - DHCP User Class" setting.
In the righthand column, enter sales-group in the "Class:" textbox. Note: It is not absolutely necessary for this name to match the name of the user group or device class, but the name entered here must match the name used in the subclass lines of the DHCP server configuration file. In this example and for clarity, the same name is used for the user group and the Class: name.
Verify the "sales-group User Setting Override" checkbox is checked. Click the "Apply" button.

The steps to configure a device class named "MDT-devices" are almost identical:

In the Mobility XE Server console, open the Client Settings page.
In the lefthand column, find the Device Setting Overrides section and highlight the "MDT-devices" entry.
In the middle section, highlight the "Virtual Address - DHCP User Class" setting.
In the righthand column, enter MDT-devices in the "Class:" textbox.Note: It is not absolutely necessary for this name to match the name of the user group or device class, but the name entered here must match the name used in the subclass lines of the DHCP server configuration file. In this example and for clarity, the same name is used for the device class and the Class: name.
Verify the "MDT-devices Class Setting Override" checkbox is checked. Click the "Apply" button.

Microsoft DHCP servers

Note: Microsoft's DHCP servers provide only limited support for this functionality, as described below:

If more than one scope is defined, only the first scope will be assigned to a specific Mobility user group or device class. Additional Mobility user groups and/or device classes will not obtain addresses from a particular scope.
If there are multiple DHCP servers available to the Mobility Server, each must be configured with the same scope and user class option.

The user class option has been defined primarily to push down DHCP options such as router, DNS, WINS, and lease information that override the default DHCP standard options configuration. User class options must be defined at the "Scope Options" level. The NetMotion Mobility XE System Administrator Guide has information on configuring the Microsoft DHCP server.

ISC DHCP servers

For ISC DHCP Servers, the following example can be followed to configure the dhcpd.conf file. This example includes a group of users ("sales-group"), a class of devices ("MDT-devices"), and an "other" class that is handled by another DHCP server.

# ... global header information...

# Multiple pool declaration

# These next three sections define three local "classes" based on DHCP user class


class "class-1" {

match option user-class;

}

#"Sales-group" below refers to the name entered in the "Class:" Mobility client setting.

subclass "class-1" "sales-group";


class "class-2" {

match option user-class;

}

#"MDT-devices" below refers to the name entered in the "Class:" Mobility client setting.

subclass "class-2" "MDT-devices";


#Class "other" will be handled by another DHCP server.

#The class is defined here only so this server knows to IGNORE it.

class "class-other" {

match option user-class;

}

subclass "class-other" "other";


subnet 192.168.0.0 netmask 255.255.0.0 {


pool {

# This is a special pool for a specific user class!


allow members of "class-1";

range 192.168.1.0 192.168.1.10;

option domain-name "domain1.com";


}

pool {

# This is a special pool for a specific user class!


allow members of "class-2";

range 192.168.3.0 192.168.3.10;

option domain-name "domain2.com";

option domain-name-servers 1.2.3.4;

}

pool {

# This is the default pool of IP addresses


range dynamic-bootp 192.168.8.0 192.168.26.254;

range dynamic-bootp 192.168.28.0 192.168.29.254;

deny members of "class-1";

deny members of "class-2";

deny members of "class-other";

}


option routers 192.168.1.1;

option broadcast-address 192.168.255.255;

}

Related Information

2166	Setting Up a Virtual IP Address Scheme
9979	NetMotion Mobility Technical Notes

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