Passive Client Feature

In this post we will learn about the passive client feature.

My Real Problem Scenario:

From last 2 weeks I am facing problem with a device connected behind a WGB. This device has static IP address.

I tried before 2 weeks and it was working but now it’s not. I don’t know what was wrong.

So on one hand it is working (At one place) – Did not enable passive client , still working

On other hand it’s not working (on another location) – Enable passive client and its working

So let’s deep drive in to this topic:

What is passive client?

Passive clients are wireless devices, such as printers, machine that are configured with a static IP address. These types of clients do not transmit any IP information when they associate with an AP. As a result, the WLC never knows the IP address unless they use the DHCP.

Must Remembering Points:

  • This feature is not supported with the AP groups and HREAP (Flex-Connect) centrally switched WLANs
  • This feature works in multicast-multicast and multicast-unicast The controller sources the multicast packets using its management IP address.
  • Earlier it was only supported on Cisco 5500 and Cisco 2100 Series Controllers but now 2504 WLC also supported.

WLCs act as a proxy for ARP requests. Upon receiving an ARP request, the controller responds with an ARP response instead of passing the request directly to the client. This scenario has two advantages:

  • The upstream device that sends out the ARP request to the client will not know where the client is located.
  • Power for battery-operated devices such as mobile phones and printers is preserved because they do not have to respond to every ARP requests.

The passive client feature enables the ARP requests and responses to be exchanged between wired and wireless clients. This feature, when enabled, allows the controller to pass ARP requests from wired to wireless clients until the desired wireless client gets to the RUN state.

How to configure:

  • Enable multicast-multicast mode
  • Enable the global multicast mode
  • Enabling the Passive Client Feature

Via GUI:

Enable Multicast-Multicast mode:

Controller > General, Select AP multicast mode and put the Multicast Group IP address and then Apply.

Passive1

Enable the Global Multicast Mode:

Choose Controller > Multicast, select both the boxes and then Apply

Passive2

Enable the Passive Client Feature:

Choose WLANs > WLANs > WLAN ID to open the WLANs > Edit page

Go to Advanced tab, Select the Passive Client box and then Apply

Passive3

Via CLI:

Enable multicast-multicast mode:

(WLC1) >config network multicast ?
 global         Enter mode.
 igmp           Igmp paratemers set
 l2mcast        Configuration of L2 Multicast
 mode           Configure WLC to AP Multicast/Broadcast traffic forwarding mode.
(WLC1) >config network multicast mode ?
 multicast      Mcast/Bcast Packets are encapsulated in multicast CAPWAP tunnel to APs
(WLC1) >config network multicast mode multicast ?
 <IP addr>      Mcast/Bcast Packets are encapsulated in multicast CAPWAP tunnel to APs
(WLC1) >config network multicast mode multicast 239.239.35.1

Enable the global multicast mode:

(WLC1) >config network multicast global ?
 enable         Enables this setting.
 disable        Disables this setting.
(WLC1) >config network multicast global enable
(WLC1) >config network multicast igmp ?
 query          Igmp Query paratemers set
 snooping       Igmp snooping configuration
 timeout        Igmp timeout set
(WLC1) >config network multicast igmp snooping ?
 enable         Enable Igmp snooping
 disable        Disable Igmp snooping
(WLC1) >config network multicast igmp snooping enable

Enabling the Passive Client Feature:

(WLC1) >config wlan passive-client enable ?
 <WLAN id>      Enter WLAN Identifier between 1 and 16.
(WLC1) >config wlan disable 8
(WLC1) >config wlan passive-client ?
 disable        Disable passive-client feature on a WLAN.
 enable         Enable passive-client feature on a WLAN.
(WLC1) >config wlan passive-client enable 8

Verification:

(WLC1) >show wlan 8
 .
 WLAN Identifier.................................. 8
 Profile Name..................................... Test
 Network Name (SSID).............................. test
 .
 .
 .
 IPv6 Support..................................... Disabled
 Passive Client Feature........................... Enabled
 Peer-to-Peer Blocking Action..................... Disabled
(WLC1) >

That’s all, now my Passive device is working 🙂

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