Trying to understand traffic Flow in a LWAPP wireless configuration.

[jrhofman]

I'm trying to understand at a high level how wireless traffic flow in the new LWAPP configuration. Based on what I can tell all wireless traffic must flow through the controllers prior to getting onto the LAN.

So lets say I have a LWAPP Access Point off an access switch in a remote closet and my controller is off my core switches. I want to communicate from my wireless PC to a wired PC on this same access switch. The traffic flows from the AP down to the core switch, through the Controller and back up to the access switch to the wired PC.

Is that correct?

If this is true my main concern is supporting APs from a central controller across a low speed WAN. Looks like I would not want to do that...

[alinn]

Hello,

You are correct that the client traffic will always flow thur the AP to the Wireless LAN Controller before being to forwarded to it final destination.

Hope this helps.

Regards,

Aaron

[amit-singh]

Hi,

Does LWAPP AP's learn the mac-address on them or is it stored on the LAN controller itself. I am just trying to understand how this actually work.

regards,

-amit singh

[phil.s]

You're right in your assumption. Data traffic travels from the client to the AP. The AP then encapsulates this data using LWAPP and forwards it to the Controller. The WLC then de-encapsulates (?) it, processes the traffic as necessary and then drops it onto the wired LAN.

So, in your scenario, the wireless client would send data to the AP. This would be encapsulated between the AP and the controller and then sent back again unencapsulated to the wired client.

Regarding using this system over a low speed WAN, there are two ways of doing this.

The first is to use a local WLC at the remote site (e.g. a WLC2006 or the new WLC network module for 2800/3800 ISR routers).

The second is to use AP1030s which are 'Remote Edge Access Points'. These aren't quite as lightweight as the rest of the 1000 Series in that they will bridge local traffic and only encapsulate traffic heading 'off site'. They will also continue to operate if connection back to the WLC is lost (the first WLAN configured on the WLC remains up on the REAP whilst connection to the WLC is lost).

I believe that the recommendation for these is a minimum of 2Mbps WAN connection.

[jrhofman]

Thank you for your insights. You seem to know the product well so I'll ask a follow up question.

Assuming you do a layer 3 type deployment (APs are crossing a L3 boundary to get to the controller), what is the purpose of the IP address on the individual interfaces you build in the controllers? I'm not talking about the management_int or the AP_managment interface but rather the interfaces that ultimately land a SSID onto a VLAN.

It seems to me that these interfaces are just a Layer 2 Pass through to the wired network where the packets then hit the LAN layer 3 interface associated with their VLAN. Can't the APs can just communicate to the IP address of the AP_management interface to get the inital LWAPP tunnels set up.

Am I thinking correctly on this?

[phil.s]

Your thinking is absolutely sound on this, and I was asked exactly the same question during a 'demo' session with a customer. Needless to say, I had no response at the time so I asked Cisco directly.

The only answer that I got was that the WLC isn't really a layer 2 device - it's a layer 3 proxy and hence requires a layer 3 address for each subnet (i.e. IP subnet associated with a layer 2 VLAN) that it has to be involved with.

For me, that isn't a full explanation, but I've not had the time to follow this up, nor had the chance to get two controllers together in multiple VLANs and see what traffic goes between the IP addresses configured in each VLAN, and what traffic goes between the AP-Management addresses.

I REALLY like the ex-Airespace product, but it's been a real nightmare over the last few months trying to get any decent, in-depth technical information out of Cisco regarding it, short of what's now available on Cisco.com.

If I get any further info on this, I'll try to remember to post it here...

[jrhofman]

Thanks Phil..... We are going to lab this out as well once we get some product in.