An engineer is configuring multicast for two WLCs. The controllers are in different physical locations and each handles around 500 wireless clients. How should the CAPWAP multicast group address be assigned during configuration?

When configuring WLCs in multicast mode, each controller must be assigned a unique CAPW-AP multicast group address. This is a critical requirement to ensure that access points (APs) only receive multicast traffic from the specific controller to which they are associated. If multiple WLCs on the same routed multicast network use the same multicast group address, an AP associated with one WLC would incorrectly receive and process multicast packets from other WLCs. This creates unnecessary overhead on the AP and can lead to unpredictable behavior.

B. Each WLC management address must be in the same multicast group. This is technically incorrect. A WLC's management address is a unicast IP address and is not a member of a multicast group.
C. Both WLCs must be assigned the same multicast group address. This is the opposite of the correct design. Using the same address would cause APs to receive multicast traffic from WLCs they are not joined to.
D. Each WLC management address must be in a different multicast group. This is technically nonsensical. A unicast management IP address cannot be "in" a multicast group; they are fundamentally different address types and concepts.

1. Cisco Wireless LAN Controller Configuration Guide

Release 8.5

"Configuring Multicast" section. The guide states

"If you are using multicast

you must configure a CAPWAP multicast group address on each controller. [...] The CAPWAP multicast group configured on the controllers must be different for each controller."

2. Enterprise Mobility 8.5 Design Guide

Chapter 4: "Wireless LAN Controller Configuration"

"Multicast" section. This guide specifies

"It is important that the multicast address be unique to the controller to ensure that the access points join only the correct controller."

3. Cisco Catalyst 9800 Series Wireless Controller Configuration Guide

Cisco IOS XE Amsterdam 17.3.x

"Configure Multicast" section. This document reinforces the principle for newer platforms: "When you enable multicast

you must configure a CAPWAP multicast group address. [...] We recommend that each controller be configured with a unique multicast group address."