Cisco WLC interface address functionality

[GVD]

Hi all,

When you create a dedicated interfaces on a WLC, the controller won't let you add it without filling in an IP address.

If one would create a new interface, let's say vlan ID 100, and disable DHCP proxy, which will send DHCP discovers into the VLAN on the network, What would be the implication of entering a dummy IP on that interface? I found this article in the community which states the IP is only used when you need to do DHCP proxy/relay from out of the controller interface, and a dummy IP will not impact client operations. Can anyone confirm or is someone able to validate?

https://community.cisco.com/t5/wireless-security-and-network/why-is-ip-address-needed-for-wlc-wlans/td-p/2553879

[Cristian Matei]

Hi,

   The IP address is used for multiple purposes, for example in case you want the controller the perform the DHCP Relay functionality (to pick up the broadcast DHCP Request from a client and relay it as unicast to the DHCP server), or for the WLC to distinguish between a Layer2 and Layer3 client roaming.

   Since you have to put an address in there anyways, why don't you put one within the subnet of the devices attached to that VLAN/WLAN in the end?

Regards,

Cristian Matei.

[GVD]

I can do that indeed. But I’m looking for other reasons besides DHCP why an IP is required and how traffic/clients will respond to a dummy IP or an IP not living in that subnet. 
I can lab test this but working from home is preventing me to do ideal testing. 

[Scott Fella]

Keep in mind that this is AireOS and not like switches. The controller interface needs an up to be able to communicate on that vlan/subnet. If you put a dummy ip for an interface, the controller will expect traffic on the configured network. This is a requirement for AireOS to communicate and pass traffic to a specific vlan.