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WLC - Does it perform client to client switching in same VLAN

Hi All,

I have two wireless clients on the same SSID and on same VLAN (and therefore on same IP subnet) associated to the same AP.

AP is CAPWAP connected to WLC. WLC is trunked to a Cat 6500 switch. All communication is working as expected.

My questions are;

1. How the traffic is switched between these two Wireless clients? Where does the switcing happen? At the AP? At the WLC?

2. Where/How to see this information.

My strong feeling is that it must be happening at the WLC, because WLC will have the MAC of Client and the AP the client is associated with. So, even if the clients are attached to two different APs, WLC will have enough knowledge to switch the traffic between.

But I did not come across any Cisco (or othter) documentation that tells how this switching happens. I can understand how the traffic gets switched between wireless and wired network, but my question how the traffic  is switched between two wireless clients on the same VLAN.

I also understand that if the clients are on different VLANs, they get routed through the wired network.

Would appreciate if anyone can clarify this or point me to the right documentation.

Thank you,

Mohan

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3 REPLIES
Hall of Fame Super Silver

Re: WLC - Does it perform client to client switching in same VLA

When an ap is in local mode, the traffic comes back to the WLC. Only in FlexConnect mode will the traffic where from the access point.

Sent from Cisco Technical Support iPhone App

-Scott
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New Member

Re: WLC - Does it perform client to client switching in same VLA

Thanks for the reply Scott.

So you are saying the WLC does the switching, because the AP tunnels all the client traffic to the WLC. Right?

Regards,

Mohan

New Member

Re: WLC - Does it perform client to client switching in same VLA

Hi,

I got this from Cisco website:

Q. How does a WLC switch packets?

A. All the client (802.11) packets are encapsulated in a LWAPP packet by the LAP and sent to the WLC. WLC descapsulates the LWAPP packet and acts based on the destination IP address in the 802.11 packet. If the destination is one of the wireless clients associated to the WLC, it encapsulates the packet again with the LWAPP and sends it to the LAP of the client, where it is decapsulated and sent to the wireless client. If the destination is on the wired side of the network, it removes the 802.11 header, adds the Ethernet header, and forwards the packet to the connected switch, from where it is sent to the wired client. When a packet comes from the wired side, WLC removes the Ethernet header, adds the 802.11 header, encapsulates it with LWAPP, and sends it to the LAP, where it is decapsulated, and the 802.11 packet is delivered to the wireless client. For more information about this, refer to theLWAPP Fundamentals section of the document Deploying Cisco 440X Series Wireless LAN Controllers.

From the above, it is clear that the wireless-client to wireless-client switching (same VLAN) is done by the WLC.

But my question here is, does WLC swtich packets based on destination IP as mentioned above? My guess would be the destination MAC address, because WLC is primarily a L2 device and does not perform routing.

Can anybody from Wireless TAC clarify how the actual switching works inside WLC.

By the way, what is MSCB (Mobile Station Control Block)? Does this have anything to do with WLC switching?

Appreciare any help.

Regards,

Mohan

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