DHCP with Vendor-Specific Options
A standards-compliant DHCP server can be configured to return the host Arubacontroller’s IP address through the Vendor-Specific Option Code (option 43) in the DHCP reply. In the Arubauser-centric network, this information can allow an ArubaAP to automatically discover the IP address of a master controllerfor its configuration and management. This appendix describes how to configure vendor-specific option 43 on various DHCP servers.
This appendix contains the following topics:
DHCP servers are a popular way of configuring clients with basic networking information such as an IP address, a default gateway, network mask, DNS server, and so on. Most DHCP servers have the ability to also send a variety of optional information, including the Vendor-Specific Option Code, also called option 43.
Here is how option 43 works:
1. The DHCP client on an ArubaAP adds an optional piece of information called the Vendor Class Identifier Code (option 60) to its DHCP request. The value of this code is ArubaAP.
2. The DHCP server sees the Vendor Class Identifier Code in the request and checks to see if it has option 43 configured. If it does, it sends the Vendor-Specific Option Code (option 43) to the client. The value of this option is the loopback address of the Arubamaster controller.
3. The AP receives a response from the DHCP server and checks if option 43 is returned. If it is, the AP contacts the master controller using the supplied IP address.
Configuring a Microsoft Windows-based DHCP server to send option 43 to the DHCP client on an ArubaAP consists of the following two tasks:
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Configuring Option 60
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Configuring Option 43
This section describes how to configure the Vendor Class Identifier Code (option 60) on a Microsoft Windows-based DHCP server.
As mentioned in the overview section, option 60 identifies and associates a DHCP client with a particular vendor. Any DHCP server configured to take action based on a client’s vendor ID should also have this option configured.
Since option 60 is not a predefined option on a Windows DHCP server, you must add it to the option list for the server.
To configure option 60 on the Windows DHCP server
1. On the DHCP server, open the DHCP server administration tool by clicking
Start >Administrative Tools > DHCP.
2. Find your server and right-click on the scope to be configured under the server name. Select Set Predefined Options.
3. In the Predefined Options and Values dialog box, click the Add button.
4. In the Option Type dialog box, enter the following information
|
Field |
Information |
|---|---|
|
Name |
Aruba Access Point |
|
Data Type |
String |
|
Code |
60 |
|
Description |
Aruba AP vendor class identifier |
5. Click OK to save this information.
6. In the Predefined Options and Values dialog box, make sure 060 Aruba Access Pointis selected from the Option Name drop-down list.
7. In the Value field, enter the following information:
8. Click OK to save this information.
9. Under the server, select the scope you want to configure and expand it. Select Scope Optionsand expand it. Then select Configure Options.
10. In the Scope Options dialog box, scroll down and select 060 Aruba Access Point. Confirm the value is set to ArubaAPand click OK.
11. Confirm that the option 060 Aruba Access Point is listed in the right pane.
Option 43 returns the IP address of the Arubamaster controllerto an ArubaDHCP client. This information allows ArubaAPs to auto-discover the master controller and obtain their configuration.
To configure option 43 on the Windows DHCP server:
1. On the DHCP server, open the DHCP server administration tool by clicking Start > Administration Tools > DHCP.
2. Find your server and right-click on the scope to be configured under the server name. Click on the Scope Options entry and select Configure Options.
3. In the Scope Options dialog box (Figure 190), scroll down and select 043 Vendor Specific Info
Figure 190 Scope Options Dialog Box.
4. In the Data Entry field, click anywhere in the area under the ASCII heading and enter the following information:
5. Click the OK button to save the configuration.
Option 43 is configured for this DHCP scope. Note that even though you entered the IP address in ASCII text, it displays in binary form.
Figure 191 DHCP Scope Values
The following is an example configuration for the Linux dhcpd.conf file.
|
|
After you enter the configuration, you must restart the DHCP service. |
option serverip code 43 = ip-address;
class "vendor-class" {
match option vendor-class-identifier;
}
.
.
.
subnet 10.200.10.0 netmask 255.255.255.0 {
default-lease-time 200;
max-lease-time 200;
option subnet-mask 255.255.255.0;
option routers 10.200.10.1;
option domain-name-servers 10.4.0.12;
option domain-name "vlan10.aa.mycorpnetworks.com";
subclass "vendor-class" "ArubaAP" {
option vendor-class-identifier "ArubaAP";
#
# option serverip <loopback-IP-address-of-master-controller>
#
option serverip 10.200.10.10;
}
range 10.200.10.200 10.200.10.252;
}