The SONOS system will require specific features enabled in a Cisco controller-based wireless system, such as the 2504 WLC, in order for reliable operation wirelessly.  Things like Airplay will not function without proper configuration.

Here is a list of features enabled on my 2504 Wireless Controller that resolved an ongoing issue where the SONOS One speakers would not “show up” on Airplay lists on my iOS devices.   The SONOS app would, however, function properly.   After months of sporadic operation, and iterative changes to configurations -- the following features proved to work well:

• Enable “Broadcast Forwarding”
• Set AP Multicast Mode to the Group Address of 239.1.1.1
• Ensure the mDNS setup includes the “Services” of AirTunes, AppleTV.  (There are other Services you can enable in the mDNS>General menu if you’d like)
• Enable Global Multicast Mode
• Enable IGMP Snooping
• Enable MLD Snooping
• Within the WLAN Configuration:
  • Under Advanced Tab…
  • Uncheck DHCP Addr. Assignment “Required” box. 
  • Check the “Passive Client” box.   (In my scenario, this proved to be the key parameter that was causing the most headache...)
  • mDNS Snooping = Enable

Note that this particular environment is relatively simple, with only (1) WLAN defined, and no VLANs == basically a flat network.   I have not attempted this in a multi-VLAN environment.  The software version tested is 8.5.182.0 and the AP environment includes models 1832, 3702, and 2702 access points, all operating in Local Mode.    

I also noticed that other client devices (certain TVs) now show up reliably in the Airplay client lists on my Apple devices.

Moderator edit: Combined posts