DHCP proxy mode - confused!

[mrjdh]

Hello,

I am working with an environment that is a bit all over the shop, when it comes to the DHCP configuration on several of the WLC interfaces. There are several SSIDs, each linked to its own interface on the controller.

In the switching environment, L3 DHCP helpers have been set on the SVI for each wireless subnet.

I have the following questions regarding the DHCP proxy feature on the WLC. I don't have time to lab this at present, but would like to know the behaviour of the following, if someone could be kind enough to assist.

1. 'Enable DHCP Proxy' feature under 'Controller >> Advanced' on the WLC - disabled/unchecked.

2. 'DHCP Proxy Mode'  set to 'Enabled' on interface linked to SSID, 2 DHCP IP addresses defined for primary and secondary fields.

Does setting the proxy mode to 'Enable' on the interface essentially mean the 2 DHCP servers in the primary and secondary fields WILL be used, even with the feature being disabled at the global level?

If I changed the interface setting to 'Global', does this mean the 2 DHCP servers defined in the pri/sec fields will not be utilised/ignored, and so the IP helpers on the VLAN SVI on the switch would be used instead?

Many thanks in advance.

[MHM Cisco World]

there are three modes:-

1- internal DHCP in WLC
2- bridge mode DHCP "here the WLC will flood DHCP request as broadcast and if the DHCP server is not in same VLAN then you need ip helper"

3- proxy mode DHCP "here the WLC will change the broadcast DHCP request send from client to unicast toward the DHCP servers, you don't need ip helper"

[craig.beck · Accepted solution]

All interfaces will ultimately use whatever is specified within its own configuration, so:

[MHM Cisco World]

there is DHCP proxy for all controller, But some case we want some WLAN-VLAN dynamic interface to 
use Proxy or not use proxy so there is additional optional in which we can config WLAN-VLAN dynamic interface to enable or disable proxy. 

[Rich R]

Nicely answered by @craig.beck - that's your answer.

[mrjdh]

Many thanks Craig. Just the answer I needed.