WLC with DHCP process

[aleopoldie]

Hello experts,

I have a question regarding the DHCP process when we have a WLC and a firewall.

Let's say we have this design, and the WLC is not the DHCP server, and it is configured as DHCP proxy disabled :

Client - AP - switch - router - Firewall - switch - WLC

When the client will request an IP address, he will broadcast his request, but on the firewall, about the flow we need to open ? We need to open the DHCP request but from which IP address ? The dynamic interface of the SSID or the management interface ?

Is it ok to configure the WLC in DHCP proxy disabled ? As I understand, that means the WLC will not modify the DHCP packet coming from the client

Thank you in advance,

Alex.

[Scott Fella]

It's fine to disable dhcp proxy. It's required if you are using the WLC as a dhcp server. The WLC is layer 2, so with dhcp proxy disabled, the request comes from the client not any interface on the controller.  You can sniff that traffic to verify also.  Typically an ip helper is used, so you would define it just like a wired vlan you have.

-Scott

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[mohanak]

When DHCP proxy is disabled on the controller, those DHCP packets transmitted to and from the clients are bridged by the controller without any modification to the IP portion of the packet. Packets received from the client are removed from the CAPWAP tunnel and transmitted on the upstream VLAN. DHCP packets directed to the client are received on the upstream VLAN, converted to 802.11, and transmitted through a CAPWAP tunnel toward the client. As a result, the internal DHCP server cannot be used when DHCP proxy is disabled.

[aleopoldie]

Hello Mohanak, Scott,

Thank you very much for your answers.

I understand the difference between DHCP Proxy enabled and disabled.

But is the DHCP packet going through the WLC even if it's configured in proxy disabled ?

On the firewall, what do we need to open as a source for the process to work ?

Source : Any ?

Destination : DHCP server IP

Regards,

Alex