Assigning the Mobility Server Address via DHCP

Technical Note 2159

Last Reviewed 11-May-2007
Applies To
Mobility version 5.01 and higher
DHCP Server for Windows 2000 and Windows 2003
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Summary

On the Mobility client (in Client Properties —> Configuration ) there are two options for specifying the Mobility server's address:

• DHCP provides server address

• Server name or IP address (where the value is hard-coded)

There are benefits to both options:

DHCP provides server address
When you use DHCP to hand out the Mobility server's address, you configure your DHCP server as described below, and when the Mobility client obtains its point of presence address from DHCP it discovers how to reach the Mobility server. The primary benefit of this option is that you don't have to hard-code any values in the Client Properties, making it easier to change the server's IP address or redirect clients to a different server pool, because you do it on your DHCP server and the change is propagated to the clients. The drawback to this option is that you must control the DHCP servers on all of the networks from which the clients will connect. If your clients are connecting over carrier WWAN networks this probably isn't an option for you; this is the reason most Mobility customers use a hard-coded server name or IP address.

Server name or IP address
There's still an option for remotely changing the server to which clients are pointed, however, without using DHCP. By using the Server name or IP address option and specifying the Mobility server's name in the Client Properties, you can later change the DNS entry for that server, redirecting clients to a different server pool, without having to reconfigure the clients. This will work regardless of the network from which the clients are connecting, and is therefore recommended over the DHCP option.

If you still want to use the DHCP option, there are two ways to set this up on your DHCP servers, described next.

Configuring DHCP to Assign Server Addresses

There are two ways to configure DHCP to assign Mobility clients a Mobility server address:

• Option 43 (DHCP Server for Windows 2000 and Windows 2003)
  This is the recommended setup. With this configuration, the address for the Mobility server can be changed without requiring the manual reconfiguration of each Mobility client. Though it only accommodates information from a single vendor, it generates less network traffic when a Mobility client connects and is simpler to set up.

• Defining a Vendor Class (DHCP Server for Windows 2000)
  For DHCP servers that support DHCPINFORM, you can create a NetMotion Vendor Class and define options to provide Mobility clients with the IP address of a Mobility server. This allows the DHCP server to provide information for more than one vendor.

  Due to changes in how Microsoft implemented the Vendor Class option in the Windows 2003 server, defining a Vendor Class for a Windows 2003 DHCP server is not currently possible with Mobility XE.

Option 43
DHCP Server for Windows 2000 and Windows 2003

To use the DHCP Vendor Specific Information option to provide Mobility clients with a Mobility server address:

1. From the Windows Administrative Tools, open DHCP and select the DHCP server you want to configure.

2. To define a Mobility server address for a particular DHCP scope, select the scope and click Scope Options. To globally define a single Mobility server address, click Server Options.

3. On the Action menu, select Configure Options.

4. In list of Available Options, select 043 Vendor Specific Info and enter the ID sequence directly into the Data entry box. In this example, the blue highlighted numbers show the hexadecimal values for an IP address of 10.128.4.5, and the green zeroes indicate the port number (if using the default port 5008 you can leave this as "00 00", otherwise enter the port in hex):

   

   Enter the ID sequence as hexadecimal: click on the left side of the edit box under Binary.

Defining a Vendor Class
Windows 2000 DHCP Server

Follow these steps to define a vendor class and set option values for Mobility XE:

1. From Administrative Tools, open DHCP and select the DHCP server you want to configure.

2. On the Action menu, select Define Vendor Classes.

3. In the DHCP Vendor Classes dialog box, click Add.

4. In the New Class dialog box, enter NetMotion in the Display name box. Position the cursor in the ASCII text area and enter NMOTCL. The hex equivalent will appear in the Binary area. Click OK.

5. Click Close in the DHCP Vendor Classes dialog box.

6. On the Action menu, select Set Predefined Options. In the Predefined Options and Values dialog box, select "NetMotion" from the Option class drop-down list. Click Add.

7. In the Option Type dialog box, the vendor class ("NetMotion") is displayed at the top. Enter the following:

   Field name	What to enter...
   Name	Signature
   Data type	Binary
   Code	001

   Click OK.

8. In the Predefined Options and Values dialog box, select "001 Signature" as the Option name and click Edit Array at the bottom of the dialog box.

9. Select the Hexadecimal radio button. In the New Value box, enter the byte values of your vendor-specific ID, including the "0x" prefix for each hexadecimal value. You must enter the bytes in reverse order (last byte first) for them to appear correctly in the Predefined Options and Values box. Click Add after entering the value for each byte:

   0x54 0x4f 0x4d 0x4e
   

   Delete any extraneous characters. When you are finished, the values should be displayed in normal byte order and look like this: 4e 4d 4f 54. Click OK.

10. Now specify an IP address for the Mobility server. On the Action menu, select Set Predefined Options. In the Predefined Options and Values dialog box, select "NetMotion" from the Option class drop-down list, and click Add.

11. Make the following entries:.

    Field name	What to enter...
    Name	NetMotion Server
    Data type	IP Address
    Code	002

    Click OK.

Configuring the DHCP Server

In the final steps, you need to configure the DHCP server for use with Mobility. This can either be done at the global or scope level: global options apply to all clients of a DHCP server, and scope-level options are applied to any clients that obtain a lease within that particular "scope" (a range of IP addresses that can be distributed).

The following steps show you how to configure the DHCP server at the scope level. The server can have more than one scope. For each one, follow these steps:

1. Highlight the "Scope Options" for the DHCP server you are configuring.

2. On the Action menu, select Configure Options.

3. In the Scope Options dialog box, click the Advanced tab.

4. Set the Vendor Class to "NetMotion" and select the check boxes next to the features you want to use with the NetMotion vendor class:

   001 Signature
   002 NetMotion Server

5. Make sure "0002 NetMotion Server" is the Option name and that the Value is set to "IP Address", then enter the Mobility server's IP address. Click OK.

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