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Cisco Wireless LAN Controller Configuration Guide
OL-17037-01
Chapter 5 Configuring Security Solutions
Configuring DHCP Option 82
Step 3 Use a wireless client to associate with an access point connected to the controller that you want to
manage.
Step 4 Enter telnet controller-ip-address and log into the CLI to verify that you can manage the WLAN using
a wireless client.
Configuring DHCP Option 82
DHCP option 82 provides additional security when DHCP is used to allocate network addresses.
Specifically, it enables the controller to act as a DHCP relay agent to prevent DHCP client requests from
untrusted sources. The controller can be configured to add option 82 information to DHCP requests from
clients before forwarding the requests to the DHCP server. See Figure 5-28 for an illustration of this
process.
Figure 5-28 DHCP Option 82
The access point forwards all DHCP requests from a client to the controller. The controller adds the
DHCP option 82 payload and forwards the request to the DHCP server. The payload can contain the
MAC address or the MAC address and SSID of the access point, depending on how you configure this
option.
Note In order for DHCP option 82 to operate correctly, you must enable DHCP proxy, which is disabled by
default. Refer to the “Configuring DHCP Proxy” section on page 4-22 for instructions on configuring
DHCP proxy.
Note Any DHCP packets that already include a relay agent option are dropped at the controller.
Note DHCP option 82 is not supported for use with auto-anchor mobility, which is described in Chapter 12.
PC or PDA with 802.11
Client and IP Soft-Phone
802.11 WLAN
IP Phone
Controller adds Option 82
payload to the request
and forwards it to DHCP Server
Access
Point
DHCP
Relay Agent
(Controller)
IP
DHCP
Server
231050
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