Guest WLAN getting IP address from data WLAN

Unanswered Question
Nov 2nd, 2009
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Hi guys,

I have a strange thing going on on our network here with our UC520 and WLC526.  I have the WLC and 2 AP521s connected directly to the PoE ports on the UC520.  The WLC is setup for 3 VLANs with the associated VLANs and networks - data (VLAN 1,, voice (VLAN 100,, and guest (VLAN 50,  I have ACLs setup on the WLC526 that should prevent from reaching  The SSIDs for data and guest are both broadcast, but different (Nomad GCS, and Nomad GCS guest).  For some reason, whenever you bring a computer up on the guest WLAN, it automatically gets a address.  If you perform an ipconfig/release and renew a couple of times, you'll eventually get an address in the range, but it doesn't happen automatically.

Some ideas:

I am only using 1 port of the WLC and the smartports are set to VLAN 1.  The second port is not connected to anything.

All laptops that we have been testing with have already been connected to the data VLAN and their MAC addresses have been added to the MAC address list.

Has anybody else seen anything like this?

Thanks in advance,


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Saurabh Verma Tue, 11/03/2009 - 05:44
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I noticed that you have "ip dhcp excluded-address" configured, however, I don't see any DHCP pool associated with this IP subnet range. For vlan 50 and vlan 100, the DHCP pools are configured fine.

UC 520 will give a DHCP IP address based on the DHCP requests that it receives and the VLAN that it receives the request on. If the request comes in on the voice vlan 100, it will give away an IP address in 10.1.1.x range, for requests on vlan 50, it will be given away in 10.0.97.x range. I would think there is some configuration issue with either the AP or the WLC due to which these devices are send DHCP request on VLAN 1 (instead of VLAN 50). Check the config on WLC and AP, if that's not the issue, you may need to open a TAC case to figure out the root cause.



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