Hello there,
I've been struggling with an issue for a while now on a 2504 WLC running the latest 8.3.102.0 code that has two (2) 2702I APs connected. I got this setup through a Mobility Express promotion that I decided to deploy in my home after running some Ethernet cables last year in my 3-level townhouse (one AP on the upper floor, the other on the lower floor). Everything is connected via a SG-300 20-port managed switch I got off Amazon. I haven't rolled out VLANs yet, so everything is flat and the APs use the Management interface untagged with a single WLAN.
I plan to expand this logically as I grow a home lab, but for now I'm just using it drive my home devices. I have five Chromecasts of varying generations running on both 2.4 and 5 GHz, a Chromecast audio, and the latest Google Home set up to serve our media streaming needs throughout the house. In addition to the chromecasts, I also have an Nvidia Shield Console that also appears like a Chromecast to my devices but is wired to the SG-300 since it's also my primary entertainment hub in the mancave along with a desktop gaming PC / media server.
I configured the 2504 WLC using the latest guide from Jan 12, 2017 as a guideline on a fresh default install which has the _googlecast._tcp.local. mDNS service string added by default in this code version it seems, so all I had to do per the guide was enable global mDNS Snooping and enable the mDNS profile in my WLAN with Aironet IE disabled as it instructs. I also had to enable IGMP snooping to get things to work initially. On the SG-300 too for good measure I have Bridge Multicast Filtering Status on Vlan 1 (Untagged) enabled for IP Group Address as a forwarding method for IPv4. I can see the group addresses it has learned as well as under Monitor > Multicast in the WLC (or 'show network multicast mgid summary' in the CLI).
For the most part, everything works as expected. I can see the Chromecasts on my phone while connected to the same SSID from within my apps. After a while though, I start to see erratic behavior I can't explain. Casting from a tab in Chrome is not an issue, but on my mobile devices, things get weird when it comes to the apps. I'm using three primarily for testing; Youtube, Google Play Movies, and Netflix since these are the apps we cast from most along with Plex for my local media server occasionally. The issues I'm seeing are Chromecasts randomly disappearing on random devices or only showing some devices. My wife and I both have Google Pixel XL phones that we got in the last few months; I can see all five Chromecasts on my Netflix app, she can only see the wired Nvidia Shield. My tablet can't see anything except on YouTube. Plex loses sight of them in the default view but it also has a refresh icon I can use to re-poll and re-populate the list that way which works; just really random and intermittent though with no discernible pattern that's driving me crazy. If the service string wasn't being queried or if the WLC wasn't forwarding multicast packets via the group address I have set (239.0.1.1) I would expect to not see anything on any devices/apps. Oh, and if I go into the Google Home app where you manage Chromecasts, I can also see all the devices fine. Casting from the apps seems to be the persistent and most visible issue.
I'm convinced something is wrong in the WLC, just having trouble pin-pointing what. As it transpires, I also have a Meraki set of gear (MR32) from past training doing guest service in my home that is also configured with the same SSID I'm using on the WLC. I can flip off the WLAN on the 2504 after flipping on the Home WLAN on the MR32, and all the devices will migrate seamlessly and can cast all the time reliably as expected in any app, even if the coverage isn't as good on a single AP set up on the main level vs two APs on the upper and lower levels converging in the middle. Again, everything is cabled to the same switch on the same LAN untagged.
I got a dump of 'debug mDns error enable' after letting it run for a good five - ten minutes I could use some help analyzing. I can also provide my WLC config since everything is on a 192.168 network. I'm at my wits end here and am this close to relegating it all to lab use only and setting up something like Google's new WiFi mesh system (might as well go all in with Google at this point, lol) so I can guarantee reliable wireless casting for the wife when I'm on travel and not have to flip over to the Meraki as a backup solution (which I would just use by default if I had another AP to cover the space in the same way since it's so much easier to manage via the Cloud and provides better analytics IMO, but I digress). I would prefer to maintain a high level of control and visibility over my network though and not have to manage my home wireless via an app only since from what I've read the Google Mesh doesn't have a web component.
If you've read this far, hopefully you feel intrigued enough to help a brother out. Thanks for any feedback or support you can provide. Happy to provide any additional details as needed!
