Saturday, October 10, 2009

Enterprise Design Guide

L2 LWAPP tunnel uses Ethertype 0xBBBB to encapsulate traffic between the AP and WLC.
L2 LWAPP does not provide corresponding CoS marking for Ethertype frames and is not able to provide transparent end-to-end QoS.

LWAPP control packet originates from UDP source port 12223
Control type 12 is the configuration command to a LWAPP AP by a WLC

AP groups do not allow multicast roaming across group boundaries.

RF group leaders exchange RRM messages every 600 seconds by default.
Maximum number of WLCs per RF group = 20

Mobility Tunneling - If uRPF checks are enabled on the next-hop routed interface, traffic is dropped after the client roams to a different subnet.

The benefit of DHCP Proxy is realized during an L3 client roam, or when a client roams across an AP group boundary.  In these cases, the WLC will receive a DHCP renewal erquest upon which it will verify the client is roaming within the mobilty group and allow the client to renew (keep) its IP address/subnet assignment even though the client roamed to a new subnet on a foreign WLC.
  • DHCP Proxy is required with asymmetric mobility tunneling.
The default behavior of the WLC is to respond to ARP queries directly based on its local ARP cache.  The WLC CLI command
         network arpunicast enable
can be used to override this behavior.  The purpose of this command is to avoid excessive retries by IP clients looking for a WLAN client that may have roamed from the WLAN network.

Broadcast & Multicast traffic
When enabled - is a global setting
-disable CDP on interfaces connecting to WLCs
-port filter incoming CDP and HSRP traffic on VLANs connecting to the WLCs
-multicast security including link layer multicast security must be considered

Centralizing WLCs
The distributed deployment model is not recommended because of current shortcomings with multicast support associated with L3 roaming.

Average LWAPP control traffic planes on the network is approximately .35kb/sec
The overhead introduced by tunneling (L3) adds 44 bytes to a typical IP packet to/from a WLAN client.  Average packet size = 300 bytes.  This is a 15% overhead increase.

Additionally, Cisco recommends that Catalyst Integrated Security Features (CISF) be enabled on the LWAPP AP switchports to provide additional protection to the WLAN infrastructure.

APs in the same physical location should be joined to the same WLC.
All APs without primary, secondary or tertiary WLC definitions will join a WLC configured for master controller mode.

Firmware changes
-Migrate APs to secondary WLC, upgrade primary WLC and then migrate APs back in a controlled manner.
AP failback should be disabled to ensure APs return to their primary WLC in a controlled manner.


  1. Hey Jennifer,
    I believe you may have listed the L2 LWAPP ethertype setting incorrectly as 0xbbbb. I'm not not specifically into wireless stuff, but do know enough generally about L2 BPDU formats to be struck by this number while examining the traffic control study (Doc ID 99947). I punched that value into the ieee search
    and got:

    "The public ETHERTYPE listing contains no match for the query bbbb"

    So, I checked out rfc 5412 which sites the value
    as 0x88bb (3.2.1. Framing) - looks like a fat finger to me. I complained to Cisco and they changed it (pdfs included, apparently, btw) but that value is still in 99947 as seen in a google web crawl pdf quick view and such. Also, Also, other docs such as Enterprise Mobility 4.1 Design Guide.

    I am really curious to check out a .pcap file or event image just to see the ethertype with my own eyes
    (dont have work or lab access). If you could steer me in that direction I'd really appreciate it.

    Good luck with the track and else (& nice work on the log, too),
    Dave Cowley

  2. Dave,
    Thanks for the corrected information, I had no idea that this was a typo in Cisco's documents. I'm not very familiar with L2 BPDU formats, so I have to take your word for it. I tried researching this about a week ago, and came up empty handed.

    You might find a .pcap file from Laura Chappell's Wireshark book website www.wiresharkbookcom & I'd bet that this is covered in the new Wireshark book she just published. I bought a copy, but haven't read it just yet (kinda busy!)

    I pulled this information out of the Cisco Mobility Design guide - this is just a collection of notes that I took on things that jumped out at me.. Here's the weblink to the pdf online. You might need a CCO login to see the pdf.

    Thanks! Jennifer

  3. is what I meant to type.

  4. Jennifer,
    I checked that out and downloaded the 'supplements' from the site. Thanks, I appreciate the suggestion - was not aware of the book but will more than likely get it.

  5. Hi Jennifer or Dave, I am looking in a L2 LWAPP pcap also. I downloaded also the supplements but I can´t find the pcap or sample to see the frame with the Wireshark. Could you finally see something? Thanks!!! John Graue

  6. John, it might be in the "Book Trace Files (222MB ZIP File)" - I downloaded that to a different laptop & haven't had a chance to open it up yet.. I'll take a look when I get some time next week.