WLC2106 Blocking DHCP?

Unanswered Question
Jul 3rd, 2007

When a client connects to the switch directly via ethernet we have no problems getting an IP. When connected to wirelessly we can not get a DHCP address, but if I set the IP to static, I then have no problems. Please note that the DHCP server being used is on the PIX firewall, and not the 2106 Controller.

The only place I see where this could be an issue is the Access Control List for the WLC2106. But this should not be the case as the current policy at the moment is to permit anything and everything.

I have this problem too.
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I am experiencing a similar issue, the place to look is in both the controllers log and also on the Pix look at running debug.

On the controller via CLI you need to do the following (Check your command reference for your specific version if the following doesn?t work)

Controller> debug

Debug ? (will display the options)

You should see debug info displayed on the terminal session.

The problem I experienced was the AP?s picked up a DHCP address no problem but clients did not, it seems to be an issue with the way the controller forward DHCP requests though we had a specific DHCP address in the controller config it appears to just broadcast it and was being picked up by another DHCP server which didn?t have an appropriate scope on it.

If you have a DHCP server other than the Pix I?d try setting up a scope on it for the appropriate address range

twaite Wed, 07/04/2007 - 11:15

You have got to be ****ing me? I have read where the WLAN controller will act like a relay agent, but now to find that a PIX will not accept these requests is disheartening to say the least. This does explain why when I brought the controller home I immediately pulled an IP address from my Linux based firewall. Now the question is will this WLC2106 provide DHCP to ALL on the network, or just to wireless clients?

How best now to enable DHCP with this controller? Right now I have the controller set to give DHCP. For the interfaces I have the virtual LAN set to, with the management interface set to On the management interface, should I set the "Primary DHCP Server" to, or do I need to put 3.10?

In the WLAN settings, should I do overide to 3.10,, or leave that alone? I assume if I do 3.1 (PIX address) there is nothing I can adjust to get the PIX to just provide an address to wireless clients on the network, or is the controller just going to get in the way? Obviously any client connected now to just an AP would be able to get an address.

This would explain why no wireless client could get an address, yet when I plugged an ethernet cable into the switch I got one right away. Part of the reason we had chosen a PIX was for the DHCP capabilities (as well as the ability to firewall two internal networks). Putting another server just to do DHCP is a little overkill in my opinion for what we need.

Here is the link to the TAC article which explains a bit more.


There?s a couple of choices, if you don?t have many clients you could statically assign clients IP?s or could test a setup running 2 DHCP servers, one on the Pix the other on the controller, I have not tested to see whether wired clients will pick up an address from the controller, I have a feeling that they won?t.

Remember that the AP?s need to be directly connected to the controller for DHCP to work.

If you do run another range on the controller you will have to insure that you have a route and covering NAT statement on the Pix.

You don?t say what Pix you have if it?s a 501 your limited to the version 6.35 because of flash & RAM and therefore stuck with the feature, the latest version if it is not a 501 is 8.02 (requires 16Mb Flash 64MB RAM) so things may change as the newer versions have more features and are becoming more like a secure router in my opinion and therefore helpful.

?Note: If you run a DHCP server on a PIX 501, the PIX does not support DHCP requests from a relay agent, which is how the WLC sends the request. You also need to configure a DHCP scope internal to the controller and remove DHCP override from the WLAN.?

I hope this helps

One other note if you upgrade software versions on the Controller, read the install notes carefully as there are specific steps.

3iadministrator Thu, 07/05/2007 - 21:50


same encounter as mine. I got a setup like this:

Internet-----PIX------L2 Switch----WLC 2106

and 2 1131APs connected directly to the L2 switch.

However I created separate Management VLAN and the client VLAN for the WLC.

Under WLC,Controller->Internal DHCP Server, Create a DHCP scope for 192.168.X.X range.

Under WLAN profile>SSID>Under interface,select the client vlan interface.and tick on DHCP addr assignment. leave the DHCP override,uncheck.

That should do the tricks.

Also go to Controller>Interfaces>Under(client vlan interface)make sure the Primary DHCP server IP is pointing to your Management Interface IP address.


jwadleigh Fri, 08/24/2007 - 10:59

You should point the Primary DHCP Server to management interface.

Also, you can use the WLC's internal DHCP server to serve wired devices, but only in version 4.0 and above. You may need to do an upgrade to get that functionality.


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