LWAPP disconnect from WLC for no reason

Answered Question
Jul 28th, 2009

Hello,

After I got everything setup right, four of my LWAPP stations stop working properly. Now, I see the green red amber blinking constantly.

I went to one of the ap and enable debug lwapp for any errors.

Well, out of 60 APs just these fours started doing this.

"could not discover any mwar"

This error keeps coming up and I don't know if they are related to the blinking error lights.

Another troubleshooting step, I notices the WLC reports only 25 access point supported.

Do you think this is related to LWAPP is the issue or something else is going with the APs?

Thanks

Correct Answer by jeromehenry_2 about 7 years 6 months ago

Par, George is right. This is how it works:

1. Your 4402-25 will not take more than 25 APs at a time.

2. When your APs discover the network, they discover the 4402-25, that returns the number of slots it supports (25), and the number of APs it already has.

3. The first 25 APs find that there is still space and join the controller.

4. All the other APs return an error message "cannot find a controller" (they find one, but it is not usable as such, as it has no available slot, so they say that they cannot find (a usable) controller.

5. These "stranded" access points keep rebooting and trying... forever.

6. Whenever one of the 25 first APs reboots / disconnects from the controller for any reason, some of the other access points may find that there is an available slot and join the controller.

7. The rebooting access point suddenly discovers that the slot is taken and returns "cannot find a controller".

There is no solution, except get some more controller slots, by sending the extra APs to another controller...

The story about "no limitation with LAG" is as follows:

- without LAG, a controller cannot take more than 48 APs on a given port, regardless of its model (this might be the part thatw as not clear in the documentation you saw): so if your controller is a 4402-25, the limit if 25 anyway. If your controller is a 4402-50 or a 4404 (100), you might be limited because of this hardware limit.

- With LAG, this hard limit disappears, and the limitation is the controller AP support (still 25 in your case, so no difference, but 50 for a 4402-50 and 100 for a 4404). But using LAG does not by magic allow your controller to support an unlimited number of APs, each controller hardware and port number and speed is built with a max number of APs in mind...

hth

J

Correct Answer by George Stefanick about 7 years 6 months ago

Par, I know the feeling. I have been there myself. You are correct 4402-25 will only ever allow 25 access point, no more than 25 can live on a controller at any given time.

If your access points are bouncing on and off the control then something is wrong. Normally once the 25 join they are solid and they shouldnt bounce. That is an issue...

The access points that join will show up under the wireless tab. These access point will be a light green when know one is on them or a dark blue if they are....

The access points not joined to the controller will flash colors over and over again in an attempt to join a controller...

Here is a good read on the join process

http://www.cisco.com/en/US/customer/tech/tk722/tk809/technologies_tech_note09186a00806c9e51.shtml

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Leo Laohoo Tue, 07/28/2009 - 18:36

Hi Pedro,

What's the color? Red/Amber only or all colors flashing at 0.5 seconds?

par13@psu.edu Tue, 07/28/2009 - 19:46

The three lights flash in sequences..the process does not stop, it keeps going over and over and over..

thanks

George Stefanick Tue, 07/28/2009 - 21:09

when you console into the ap and reboot it does it join the controller?

Not sure what you mean about the 25 ap supported ...

what controller do you have ?

par13@psu.edu Wed, 07/29/2009 - 03:22

hi,

thru the web management portion, on top of the WLC 4402, there is a line located on the very right hand side of the WLC pitcure that says 25 Access Points Supported.

Now, I do not think this is related to the issue but it got my attention that the WLC web management portion is reporting this information.

Now, as far the APs, they are configure to work as LWAPPs. Yesterday, late in the afternoon, four APs 1220 model stop working.

The normal function is one solid green and another blinking green light. Basically, two lights are showing green indicating normal function.

The four APs, not working, have a series of blinking red - green - amber. I checked on cisco online and the website reports the color code as APs not able to find the WLC.

First, the APs are plug on the same switch where other 10 APs are just fine. No configuration on the switch has change and the only APs complaining are only these fours.

1. I have rebooted the APs -- no success

2. I have reset pusing the mode buttom at the same time connecting the ethernet cord (POE) to the AP. --- no success

3. I have read Cisco troubleshooting steps that say about making sure option 43 (DHCP) is setup --- Check

Can you help?

Thanks

Leo Laohoo Wed, 07/29/2009 - 18:57

Hi Pedro,

All colors flashing means that the AP can't find the WLC.

1. Check if the AP has a valid IP address.

2. Can the AP ping the WLC Management IP address?

If the AP can ping the WLC Management IP address, console into the AP and in enable mode type in the command lwap ap controller ip address .

Hope this helps. Please rate when applicable or helpful.

par13@psu.edu Fri, 07/31/2009 - 16:08

I have noticed at the home page of the WLC, it says on the top 25 access points supported.

Now, I read in cisco documentation that if LAG is running the number of access points supported are not limited anymore.

Why my 4402 keeps limiting my view to just 25 access points and not 60 access points that we currently have

George Stefanick Fri, 07/31/2009 - 16:43

What model 4402 do you have 25 or 50?

If you have 4402-25 regardless you will only ever get 25 to connect. Same is true with the 50 as well..

Without LAG you can only connect a max of 48 aps (going off mem -- may be less someone else chime in) so if you had a 4402-50 with 1 ap manger and 1 interface your getting 48 aps on that controller at best... you go lag you can get all 50 ...

Its best to read the deisgn guide. With the great hands on you are getting one solid read of the manual will put you on the right track ...

par13@psu.edu Fri, 07/31/2009 - 19:54

I believe the model number is 4402-25. It has two fiber connection, and both are configured to work as one using LAG and at the router using port channel.

Still, I have seen APs showing on the management portion and then disapear. Other APs shows on the management consult and then disapear.

Basically, the WLC do not allow the APs to stick forever.

Therefore, my question for you guys is, if the APs keeps apearing and disapearing,

Are they getting my configuration set on the WLC 4402-25, for ssids,vlans, and so forth?

thanks

Leo Laohoo Fri, 07/31/2009 - 21:11

Don't confuse yourself with the WLC4404-100. For each 4400 port, it will support up to 48 APs. For a 4402-25, it will support up to 25 APs in total. If you have 60 APs, then you need to get a 4402-50 (additional controller) or a 4404-100.

There are many reasons why your APs will JOIN and un-JOIN from the controller. What does the logs of your controller say? What does the logs from the LWAP say?

Before the AP can download the configuration it has to successfully join the controller. So don't worry about your SSID, VLANs, WLANS configuration because it only muddles the issue.

I agree with George, please go through the Design Guide or the Deployment Guide. The more topic you create the more confusion, rather than solutions, you will be faced due to lack of understanding or knowledge.

par13@psu.edu Sat, 08/01/2009 - 03:47

Don't missunderstand the reason for my questions. Believe me, I have been reading lots of cisco material on this area. It's just sometime the material says something and later on says something else.

But, going back to what you said, if I understood correctly, the 4402-25 can only support 25 AP at a given time.

In my case, I have 60 APs. Therefore, after I have setup all the necessary information on the WLC, all 60 APs will be receiving the configuration information from the WLC as the AP appear and/or disappear.

Correct Answer
George Stefanick Sat, 08/01/2009 - 05:40

Par, I know the feeling. I have been there myself. You are correct 4402-25 will only ever allow 25 access point, no more than 25 can live on a controller at any given time.

If your access points are bouncing on and off the control then something is wrong. Normally once the 25 join they are solid and they shouldnt bounce. That is an issue...

The access points that join will show up under the wireless tab. These access point will be a light green when know one is on them or a dark blue if they are....

The access points not joined to the controller will flash colors over and over again in an attempt to join a controller...

Here is a good read on the join process

http://www.cisco.com/en/US/customer/tech/tk722/tk809/technologies_tech_note09186a00806c9e51.shtml

Correct Answer
jeromehenry_2 Sat, 08/01/2009 - 08:31

Par, George is right. This is how it works:

1. Your 4402-25 will not take more than 25 APs at a time.

2. When your APs discover the network, they discover the 4402-25, that returns the number of slots it supports (25), and the number of APs it already has.

3. The first 25 APs find that there is still space and join the controller.

4. All the other APs return an error message "cannot find a controller" (they find one, but it is not usable as such, as it has no available slot, so they say that they cannot find (a usable) controller.

5. These "stranded" access points keep rebooting and trying... forever.

6. Whenever one of the 25 first APs reboots / disconnects from the controller for any reason, some of the other access points may find that there is an available slot and join the controller.

7. The rebooting access point suddenly discovers that the slot is taken and returns "cannot find a controller".

There is no solution, except get some more controller slots, by sending the extra APs to another controller...

The story about "no limitation with LAG" is as follows:

- without LAG, a controller cannot take more than 48 APs on a given port, regardless of its model (this might be the part thatw as not clear in the documentation you saw): so if your controller is a 4402-25, the limit if 25 anyway. If your controller is a 4402-50 or a 4404 (100), you might be limited because of this hardware limit.

- With LAG, this hard limit disappears, and the limitation is the controller AP support (still 25 in your case, so no difference, but 50 for a 4402-50 and 100 for a 4404). But using LAG does not by magic allow your controller to support an unlimited number of APs, each controller hardware and port number and speed is built with a max number of APs in mind...

hth

J

par13@psu.edu Sat, 08/01/2009 - 15:57

Guys,

You have been magnificent with this last two submissions. You have answered my biggest concern.

Thanks for all the help on this forum...

Thanks again

George Stefanick Sun, 08/02/2009 - 12:08

Par,

I would like to extend the offer to you for a quick phone call. If you need help conatct me at my web site my80211.com. We can exchange contact inforamtion.

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