topic Re: Cisco WLC interface address functionality in Wireless

Cisco WLC interface address functionality

GVD — Mon, 05 Jul 2021 18:52:46 GMT

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

Re: Cisco WLC interface address functionality

Cristian Matei — Fri, 20 Mar 2020 18:15:05 GMT

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.

Re: Cisco WLC interface address functionality

GVD — Fri, 20 Mar 2020 18:34:20 GMT

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.

Re: Cisco WLC interface address functionality

Scott Fella — Fri, 20 Mar 2020 21:39:48 GMT

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.