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ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Welcome to the Cisco Networking Professionals Ask the Expert conversation. This is an opportunity to discuss with Cisco expert Steve Rodriguez about the configuration of the Cisco unified wireless network architecture. Steve is a customer support engineer in the San Jose Technical Assistance Center (TAC) for the wireless network products. He is responsible for trouble shooting Cisco wireless products from the autonomous access points up to the Wireless LAN Controllers in the LWAPP structure.

Remember to use the rating system to let Steve know if you have received an adequate response.

Steve might not be able to answer each question due to the volume expected during this event. Our moderators will post many of the unanswered questions in other discussion forums shortly after the event. This event lasts through December 22, 2006. Visit this forum often to view responses to your questions and the questions of other community members.

157 REPLIES

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Ian,

I would be the correct guy to ask, can you post a copy of the config? From what you are describing, it could be a couple of things and seeing the config will greatly help me in determining the issue.

HTH, Steve ------------------------------------------------------------------------------------------------ Please remember to rate useful posts, and mark questions as answered

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

When will CSCse93986 be fixed in the WLC 4.0 train?

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Darren,

It looks like this fix should be in the next MR, due out this month.

HTH, Steve ------------------------------------------------------------------------------------------------ Please remember to rate useful posts, and mark questions as answered
New Member

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Steve,

Cisco 877W IOS 12.4(11)T

I have attached a Cropped config

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Ian,

One thing I would recommend is chance the wep key index from 2 to 1. In wep you can have up to 4 keys, but if the client can't define key 2 you will have issues. So try moving this to key 1. you will first need to remove the index 2, since the ISR can only handle one wep key. Also, you don't need the ip helper-addresses on the interfaces, they aren't hurting anything, but I tend to prefer removing unneeded commands.

HTH, Steve ------------------------------------------------------------------------------------------------ Please remember to rate useful posts, and mark questions as answered
New Member

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Cisco 877W IOS 12.4(11)T

Steve,

Thanks I now have DHCP working fine, but no traffic. I'll work through config this evening (UK time).

New Member

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Cisco 877W IOS 12.4(11)T

Personal Firewalls don't we just love them!

AAAAAAAAAAArggggggggggggghghh

Thanks for your help Steve...all sorted

IanC

Bronze

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Hi Steve, I read client load-balancing from following link:

http://www.cisco.com/univercd/cc/td/doc/product/wireless/control/c44/ccfig40/c40rrm.htm#wp1108498'

But I got confused about this client load-balancing with Aggressive load-balancing. What are the difference between them?

Thanks

Zhenning

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Zhenning,

That is a very good question. The difference between Aggressive Load Balancing and Client load balancing, is basically when and how this happens.

Aggressive load balancing, happens when the client attempts to join initially. The AP will send a reason code of 17, that tells the client it is too busy to handle any more clients at that time. If the client still try's to join, we let them join on the 4th attempt.

Client load balancing is a function of RRM, and is used by the WLC to force some clients to move from one AP to another nearby AP so that the load is eased up a bit. As the document states, this is only valid on AP's on the same controller.

Hopefully this has answered your question but if not please let me know and I will try to go a little more indepth on this.

HTH, Steve ------------------------------------------------------------------------------------------------ Please remember to rate useful posts, and mark questions as answered
Bronze

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Steve, thank you for your explaination. I still have two things not clear:

1. In Client load balancing, how does WLC force client move from one AP to another?

2. Among APs on the same controller, is aggressive LB same as client LB?

Thanks

Zhenning

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Zhenning,

For Client load balancing, the controller uses RRM to roam the client from the AP they are on, to an AP that is less busy. No connectivity will be lost when this happens.

As for the second question, they are similar but not quite the same. Aggressive LB, will try to keep an AP from joining if it is busy, but will still allow the client to join on it's 4th attempt, while Client LB is used to move clients to less busy APs in a congested area.

HTH, Steve ------------------------------------------------------------------------------------------------ Please remember to rate useful posts, and mark questions as answered
New Member

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

hi steve i am new to wireless. i have recently bought 2 1231g acess-points can they be configured by the WLC.

and can these access-points work as bridges also.

regards

sebastan

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Sebastan,

The answer to both questions is yes...but not at the same time.

The 1231 can be converted to run the LWAPP code and be controlled by the WLC. This requires the Conversion tool, and the LWAPP image to be done. Both can be downloaded from CCO on the Wireless Software page. Here is the link to the documentation on how to convert and IOS AP to LWAPP

http://www.cisco.com/en/US/products/hw/wireless/ps430/prod_technical_reference09186a00804fc3dc.html

The 1231, can also act as a bridge between two buildings, but only in IOS mode. The only AP's that are currently able to be bridges for the WLC are the 1030 LWAPP AP. Here is a link to the configuration guide for how to configure an AP as a bridge.

http://www.cisco.com/application/pdf/en/us/guest/products/ps4076/c2001/ccmigration_09186a0080606a87.pdf

HTH, Steve ------------------------------------------------------------------------------------------------ Please remember to rate useful posts, and mark questions as answered
New Member

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Hi Steve,

I have a newly installed WLC system (a 2006 with 4 1241 WAPs) - running the latest WLC firmware.

We are having a problem in our office with flapping - clients initially joining the strongest access point, and them intermittenly roaming to a further access point with poor performance. After a few minutes the client may join the stronger WAP again.

I have a basic installation - and haven't changed many defaults except to disable agressive roaming (which I now understand doesn't affect clients already associated).

My question is - how common is this issue? Does this sound more like a problem caused by RRM or by poor implementation of Dell client drivers? BTW - the Dell client settings are set to defaults - except for VLAN priority support - which is disabled.

Thanks,

Joe Matus, CCIE

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Joe,

The logic to roam from one AP to another is all on the client. Without knowing anything further I would say look at the client, and see if you can manipulate what factors the client is using to roam. A question for you, what type of NIC is in the laptop?

HTH, Steve ------------------------------------------------------------------------------------------------ Please remember to rate useful posts, and mark questions as answered
New Member

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Thanks Steve. The client we are using is the Dell Wireless 1390.

Regarding the roaming - I figured the roaming logic is all in the client - I was thinking if RRM had something to do with it.

When using a wireless monitor, I noticed on occasion - maybe every 30 seconds - the SNR drops from an average of 45 to 7 - for a split second, and it's the signal strength that drops, not the noise level increasing. Is this sudden drop normal?

Thanks

Joe

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Joe,

A drop in the signal would be expected, since any interferance whether frequency or structurally could cause this. A drop from full bars to no bars, I would not expect, but can happen depending on what all is going on in the air. I would recommend getting a wireless sniffer trace when the drop happens to see if any interference can be seen.

HTH, Steve ------------------------------------------------------------------------------------------------ Please remember to rate useful posts, and mark questions as answered
New Member

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

hi steve can u pls tell me what is the difference between ios ap and lwapp. i am new and dumb abt wireless .

and abt the wlc i read it;s basically for central management of access-points right. does it do management of bridges also???.

i have recently bought a wlc 2000 series also. is it possible on it.

pls reply.

regards

thanks once again

sebastan

New Member

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

hi steve here;s a setup i am trying to do can u pls help.

i am having 2 access-points ap1 and ap2 and i have a wireless client. right now i am not using the WLC.both the ap;s are 1231g

i want my user to connect to the ap1 and get authenticated by 802.1x authentication.at the same time can my ap1 work in bridge mode with ap2.and my ap2 is connected to my internet router via ethernet.

is this setup possible. can u pls help. thanks once again.

regards

sebastan

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Sebastan,

The difference between IOS and LWAPP, is:

In an IOS deployment, all configurations are all on the AP itself, and they can run as a single standalone unit. All configurations, software upgrades would need to be done on a per AP basis.

I tend to think of the LWAPP AP as a "thin client". The AP itself has a very small image on it, that only has enough configuration stored to be able to reach out and find the controller(s) that it knows of. After that, all the configuration gets pulled to the AP from the controller. All changes, software upgrades etc, come from the controller, and do not need to be done individually on the AP.

HTH, Steve ------------------------------------------------------------------------------------------------ Please remember to rate useful posts, and mark questions as answered

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Sebastan,

The WLC does not support bridging at this time. But yes, the WLC is designed to centrally manage the LWAPP AP.

HTH, Steve ------------------------------------------------------------------------------------------------ Please remember to rate useful posts, and mark questions as answered
New Member

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

dear,

I was installed the (remote agent) in the PC (also the Cisco works installed in this PC)first, its work but when the IT manager regenerate the certificate in the ACS and install it on the client its not work .just I can established connection to the internal database but the external database(windows ACTIVE Directory )its not connected and the ACS report its INTERNAL ERROR ,the Microsoft flag in the remote agent its appear on the ACS ,please advice me

New Member

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Steve,

For client load balancing to work properly, is it necessary for the client to support CCX ? If yes, what version.

What about so called "sticky" clients ? How are they forced to associate to another AP ?

Thanks,

Chris.

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Chris,

It is not necessary that the client support CCX. The funtion for the load balance is an attempt on the WLC's part to get the client to move, or associate to a different AP. But that logic is on the client.

HTH, Steve ------------------------------------------------------------------------------------------------ Please remember to rate useful posts, and mark questions as answered
New Member

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Steve,

Thanks for the answer. To go a little deeper: how does the WLC attempt to have the client move to another AP ?

Thanks,

Chris.

New Member

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

The company I work for uses the Novell client on all PCs. :(

Buying the Funk Software supplicant or buying or loading anything extra on the PCs is not allowed.

Currently we use the BBSM as a generic WLAN hotspot. The BBSM authenticates to Novell using RADIUS.

So the user must:

1-login locally to PC

2-login to BBSM

3-login using the Cisco VPN client

4-login to Novell

Is there now a better way to implement WLAN for Novell using the Wireless LAN controller Network Module?

Thanks!

Tim

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Tim,

I understand your pain. The problem is, you need a supplicant that can login to the network, before the user login has happened. I know that the Cisco ADU and CSSC, and the Intel supplicantes can do this. You might be able to still use wireless, in much the same way you are now except for the need to VPN. You could setup the WZC to connect to the appropriate network, and still login locally. Then after you have logged in, you would then be able to login to Novell. The one caveat that I'm aware of, is you need to let the Novell logout happen before you shut down windows.

HTH, Steve ------------------------------------------------------------------------------------------------ Please remember to rate useful posts, and mark questions as answered
New Member

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

Thanks for answering my question.

New Member

Re: ASK THE EXPERT - WIRELESS LAN CONTROLLERS

What is the status LED on the 4400 Wireless LAN Controller used for? What information can you get from it?

For example, I have a 4402 Wireless LAN Controller and the status LED is a solid green light. Currently I can not access the controller via web interface, telnet, SSL, or directly connected to the console port. I can't seem to find reference to why this is happening.

Thanks,

Al May

Network Engineer

Naperville School District 203

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