WLC 4402 with 6.202 can't give dhcp to clients

[benbollinger]

When on the management interface the clients can't get dhcp but the AP's can on the same vlan.   I've tried enabling and disabling dhcp proxy,  and using a remote dhcp server as well as the internal server.   This same config works on the 4402 we're replacing with version 5.2.193 on it.

Any suggestions?

[George Stefanick]

In the WLC -- CONTROLLER tab click on the managment interface. Do you have a DHCP server entered ?

[benbollinger]

Yes.  I've tried enabling the local pool and setting the management ip as the server,  or using dhcp on a router(which is working if i switch back to the 5.2 device we're RMA'ing) and then setting the dhcp server to the ip of the router giving out dhcp.

[Surendra BG]

Toggle DHCP proxy feature on the WLC and see if that helps!!

WLC GUI >> Controller >> Advanced >> DHCP >> PROXY >> (Toggle)

Regards

Surendra

[benbollinger]

I tried that as well following some posts I saw on here last night.

[George Stefanick]

Click on your WLAN and then Advance -- Do you have override checked?

[George Stefanick]

Did you reboot the controller after the toggle of the proxy ?

[benbollinger]

I can try that.  I did so many things over a 4 hour period that I can't be sure when I rebooted.  Is that mandatory for the proxy change to take effect?

You only need the proxy if you're using a external dhcp server,  correct?

I definetly tried the internal one too.  Do I need to reboot when I enable the internal scope as well?

[George Stefanick]

No you dont need to reboot after either of those settings. But, as Ive learned sometimes the WLC will hiccup. And based on your post it sounds like you have the right settings and you know what your're doing...

So reboot her and see if this works...

[Surendra BG]

I guess we need to disable if we have the pool on the external server and we should have the ip helper under the int vlan.

provide the below output

sh run-config (not show running-config) from the WLC

sh run int <> (Switchport config)

WLAN in concern

Regards

Surendra

[Surendra BG]

forgot to ask!! wat does the debug say??

debug client

Regards

Surendra

[benbollinger]

At 7am I had to put the old one back in service so I'll have to get that info as soon as I can get someone to plug it in after hours again for me.  Probably Monday night.  Thanks to the both of you. 

[George Stefanick]

Keep a mental note. If you turn off PROXY you need to use helpers on the routers. If you dont, clients wont get an IP. When a WLC is in proxy mode, it will UNICAST the dhcp from the interface the client is in to the DHCP server. So no helpers are need.

[nallcott]

I am having the same issue with a 4402-25 controlling 14 LWAPs (1420 series) using 6.188. The configuration is fairly simple where the WLC is connected via a 1 Gigbit trunk to a 3750 switch. 3 vlans are being used and mapped to 3 WLANS. Two of the WLANs are secured and are using the internal DHCP of the WLC configured with two ranges on the same subnet as the dynamic interfaces assigned to these WLANs. Clients authenticating on these WLANs can pull an IP address from the WLC internal DHCP server without issue. The address of the management interface is assigned as the DHCP server for both dynamic interfaces assigned to these WLANs. And global DHCP proxy is enabled. This is the standard internal DHCP server configuration and it is working.

The problem is the open WLAN used for guests. There is an ASA5505 device configured as an external DHCP server within the VLAN mapped to the guest WLAN. The ASA interface has been assigned an IP address within the VLAN subnet and acts as an Internet gateway as well for the guests. DHCP proxy is globally enabled and the IP address of the external ASA DHCP server is added to the guest dynamic interface. I can pull an IP address for a client laptop that needs dynamic IP assignment by plugging a patch cable connected to the laptop into one of the 3750 access ports that are assigned on the guest VLAN. However, if I disconnect the laptop and plug a patch from the ASA GW/DHCP interface into that same guest VLAN port, I can't pull an IP address with the same laptop in wireless mode when connecting to the guest WLAN.

Traces on the laptop show the bootp (DHCP) discovery broadcasts leaving the laptop and nothing returning.

My hunch is that there is a setting, (AP-MAC/AP-MAC-SSID), on the same screen as the DHCP proxy enable control. Currently that setting is set to AP-MAC. Possibly the DHCP messages need the SSID information as well to make it back to the correct WLAN, because 3 are being used on each LWAP. I don't know how the Cisco dudes coded their tunnel decoder. I probably would have broadcast any DHCP server return down all WLANS on that LWAP. But maybe that's the information that's needed? Don't know? Not written about in all the repeating Cisco docs either. Can't test this theory until Tuesday when I get back to site. Does anyone have some more information about these curious settings?

Another thought was that maybe the external DHCP server must be specified on the AP manager interface and not on the guest interface since the AP manager interface is the one that talks with the LWAPs for control purposes. Maybe it parses the tunnel DHCP discovery messages and talks with the DHCP server on the guest VLAN. Although in my situation the external DHCP server must be physically present on the guest VLAN because of the IP addressing and the fact it is operating as an Internet gateway, it could have been placed on any interface associated with the WLC. Since the WLC can route, it could communicate with a DHCP server and deliver the DHCP proxy functionality and client IP addresses for any subnet. Again, I don't know if this is the situation? It ain't written down all that clearly anyhow in the repeating Cisco docs, and I can't test until I get back to site on Tuesday. If anyone has some info...

Otherwise this has to be a bug in the WLC software that was introduced?

Sincerely,

Nate