Cisco Wireless LAN Controller Configuration Guide, Release 7.4
Configuring DHCP Proxy
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Configuring DHCP Proxy

Configuring DHCP Proxy

Information About Configuring DHCP Proxy

When DHCP proxy is enabled on the controller, the controller unicasts DHCP requests from the client to the configured servers. At least one DHCP server must be configured on either the interface associated with the WLAN or the WLAN itself.

When DHCP proxy is disabled on the controller, those DHCP packets transmitted to and from the clients are bridged by the controller without any modification to the IP portion of the packet. Packets received from the client are removed from the CAPWAP tunnel and transmitted on the upstream VLAN. DHCP packets directed to the client are received on the upstream VLAN, converted to 802.11, and transmitted through a CAPWAP tunnel toward the client. As a result, the internal DHCP server cannot be used when DHCP proxy is disabled. The ability to disable DHCP proxy allows organizations to use DHCP servers that do not support Cisco’s native proxy mode of operation. It should be disabled only when required by the existing infrastructure.

Note


DHCP proxy is enabled by default.


Restrictions on Using DHCP Proxy

  • DHCP proxy must be enabled in order for DHCP option 82 to operate correctly.
  • All controllers that will communicate must have the same DHCP proxy setting.

Configuring DHCP Proxy (GUI)


    Step 1   Choose Controller > Advanced > DHCP to open the DHCP Parameters page.
    Step 2   Select the Enable DHCP Proxy check box to enable DHCP proxy on a global basis. Otherwise, unselect the check box. The default value is selected.
    Step 3   Click Apply to commit your changes.
    Step 4   Click Save Configuration to save your changes.

    Configuring DHCP Proxy (GUI)


      Step 1   Choose Controller > Interfaces.
      Step 2   Select the interface you want to configure the DHCP proxy. You can configure the DHCP proxy on the management, virtual, ap manager, or dynamic interfaces in the controller. The Interfaces > Edit page is displayed with DHCP information on the primary and secondary DHCP servers configured in the controller. If the primary and secondary servers are not listed, you must enter values for the IP address of the DHCP servers in the text boxes displayed in this window.
      Step 3   Select from the following option of the proxy mode drop-down to enable DHCP proxy on the selected management interface:Global—Uses the global DHCP proxy mode on the controller.Enabled—Enables the DHCP proxy mode on the interface. When you enable DHCP proxy on the controller; the controller unicasts the DHCP requests from the client to the configured servers. You must configure at least one DHCP server on either the interface associated with the WLAN or on the WLAN.Disabled—Disables the DHCP proxy mode on the interface. When you disable the DHCP proxy on the controller, the DHCP packets transmitted to and from the clients are bridged by the controller without any modification to the IP portion of the packet. Packets received from the client are removed from the CAPWAP tunnel and transmitted on the upstream VLAN. DHCP packets directed to the client are received on the upstream VLAN, converted to 802.11, and transmitted through a CAPWAP tunnel toward the client. As a result, the internal DHCP server cannot be used when DHCP proxy is disabled.
      Step 4   Check the Enable DHCP option 82 checkbox to ensure additional security when DHCP is used to allocate network addresses, check the Enable DHCP option 82 checkbox.
      Step 5   Click Apply to save the configuration.

      Configuring DHCP Proxy (CLI)


        Step 1   Enable or disable DHCP proxy by entering this command:

        config dhcp proxy {enable | disable}

        Step 2   View the DHCP proxy configuration by entering this command:

        show dhcp proxy

        Information similar to the following appears:

        
        DHCP Proxy Behavior: enabled
        

        Configuring DHCP Proxy (CLI)


          Step 1   Configure the DHCP primary and secondary servers on the interface. To do this, enter the following commands:
          • config interface dhcp management primary primary-server
          • config interface dhcp dynamic-interface interface-name primary primary-s
          Step 2   Configure DHCP proxy on the management or dynamic interface of the controller. To do this, enter the following command:
          • config interface dhcp management proxy-mode enableglobaldisable
          • config interface dhcp dynamic-interface interface-name proxy-mode enableglobaldisable.
          Note    To ensure additional security when DHCP is configured, use the config interface dhcpinterface typeoption-82 enable command.
          Step 3   Enter the save config command.
          Step 4   To view the proxy settings of the controller interface enter the show dhcp proxy command.

          Configuring a DHCP Timeout (GUI)


            Step 1   Choose Controller > Advanced > DHCP to open the DHCP Parameters page.
            Step 2   Select the DHCP Timeout (5 - 120 seconds) check box to enable a DHCP timeout on a global basis. Otherwise, unselect the check box. The valid range is 5 through 120 seconds.
            Step 3   Click Apply to commit your changes.
            Step 4   Click Save Configuration to save your changes.

            Configuring a DHCP Timeout (CLI)

            Configure a DHCP timeout by entering this command:

            config dhcp timeout seconds