For anyone watching this or for future reference...
Issue: UPNP Multicast group used by chromecast not permitted by default
Resolution: Enable multicast group 239.255.255.250 on the wireless controller from the Web GUI with the following process:
- Click Controller > Network > Topologies
- Click the Topology Chromecast is connected to
- Click Multicast filters tab
- Click Multicast Bridging check box
- Click IP group Radio button and add 239.255.255.250/32
- Click Save
Doug Hyde
Director, Technical Support / Extreme Networks