WLC 4402 wont discover APs

Unanswered Question
Mar 11th, 2008

Good day

Recently my WLC 4402 started losing Aps,i cleared all the configs in the WLC and reconfigured the WLC,now its unable to discover APs,Does anyone know what might be causing the problem.

I have this problem too.
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I am assuming that you are running the controller in layer 3 mode and that the WLC is on a different subnet/VLAN.

1) There should be a route between the VLAN/Subnet. At a minimum, this route would need to permit LWAPP traffic in both directions.

2) If the controller has changed IP addresses since the LWAPs were connected to it, the LWAPs need to be directed to the controller. This can be done most easily with a DNS entry the points to the controller or via a DHCP option.

3) We have sometimes observed that the Ethernet switches that carry the LWAP traffic may not carry the VLAN all the way back to the controller. Somewhere along the way a VLAN may be missing from a trunk and/or the switch(es) connected to the LWAPs are no longer on the VLAN.

4) If you are using DHCP to assign IP addresses to the LWAPs, you will need to make sure that this service is available to the access points.

5) You may want to check your AP Manager interface to make sure that it still has the correct IP address and subnet mask.

6) If you have gone through these various checks, and have verified all your other settings, I have also found that powering down the LWAPs and powering them back up (after 10 seconds or so) has fixed a number of problems.

7) As an afterthought, if part of your WLC 'reconfiguration' included an upgrade to 5.0.148 and your APs are 1000 (AirSpace) series access points, you may not have been aware that support for these older models is no longer present in the newer code.

I hope that this at least gives you some ideas...

- John

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Scott Fella Tue, 03/11/2008 - 21:11

You need to specify what ap's and what code you are running.... and what changed before you started having issues.

akobwaycct Tue, 03/11/2008 - 22:42

hi fella5,

i am using LAP1242 and the controller is a 4402 running

there are about 20 LAPs in the network,the WLC started by losing 11 Aps and in an attempt to discover the lost APS i issued the reset system command,there after all the other Aps got lost.I did a new configuration and till now the WLC cannot register the LAPs.

Scott Fella Wed, 03/12/2008 - 06:13

What I would do is setup one of the switch port that an ap is attached to on the same vlan as the management vlan on the wlc. Make sure you have dhcp on that management subnet so tha ap can join the wlc. Also verrify the time is set on the wlc.

akobwaycct Wed, 03/12/2008 - 06:26

that i have done,the aps are on the same vlan as the management,how does time fit in ?i have also upgraded the WLC to image 4.0.171 but there is no change.

sabhasin Wed, 03/12/2008 - 06:39

can you provide the output of "debug lwapp events enable" from the WLC, when the APs are trying to find the WLC?

Scott Fella Wed, 03/12/2008 - 06:47

Setting the ntp or the time manually is an important step for the ap's to be able to join the controller. the time has to be within around 5 minutes of actual time or else the ap's will not join and go throught the cycle of joinging a controller and reboot. if this is set, you need to console into one of the ap's and look at what the log is showing. Copy and paste this so we can see the output. Also run the debug commands as previously mentioned.

akobwaycct Wed, 03/12/2008 - 07:34

ok thanks for the information but the time on the WLC is ok.

I cannot get any oputput from the "show debug lwapp events" command on the controller.

i went in to one of the aps like you suggested and the output is attached on the file.

Scott Fella Wed, 03/12/2008 - 09:10

Well if you look at the output, you can see that the ap stops at the Discovery process which is wrong. the only time I have seen this is when the image gets corrupted. this could of happened during the code upgrade in which the ap's started to download the code during the wlc code upgrade and then the wlc rebooted or was rebooted. if this is what happened, then you can try to reset the ap using the reset button or convert the ap to ios then back to lwapp. I don't know of any other way.

sabhasin Wed, 03/12/2008 - 23:05

yep, nothing after LWAPP Discovery....did you leave it running for a while? also, how are the APs being told about the controller? DHCP Option 43? DNS? anything else?

Scott Fella Thu, 03/13/2008 - 05:34


He mentioned that the ap's are on the same subnet as the management/ap-manager interface.

sabhasin Thu, 03/13/2008 - 07:24

fella5 - yeah, i missed that...Doh! anyways, i went back and read and looks like the command he might have entered on the WLC for debugs might have been wrong. From his post, i see that he ran "show debug lwapp events"...The actual command is "debug lwapp events enable".

Scott Fella Thu, 03/13/2008 - 07:39

The thing is that when you are consoled into one of the ap's, you should see the normal events that the lwap goes though, which in the output you have doesn't show. Did you noticed that when you were upgrading that the ap's status was downloading? If the WLC goes through the reboot during this process then you have a corrupt image in the lwap. You will have to convert to IOS then back to lwapp.

Here an an output from my test ap


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