Ah, IIRC I needed this for other devices (can’t remember if it was Bluesound support that suggested it or BT for IPTV). Works for me (on the same switch), but obviously everyone’s setup is different.
Curious. Disabling power management never did anything for me. I just updated NetGear firmware to 2.00.12 (thanks for mentioning the update) and tried to turn on IGMP snooping. Pixel 2 would not connect to the core. Turned IGMP snooping off. Pixel 2 connected immediately.
Well that certainly seems clear cut! I wonder what accounts for the differences? I doubt we’ll ever know!
Tried this tonight. So far so good. Brilliant!
Brian
My suspicion from many months of trying to debug this, on my own and with Roon engineers, is that it is a subtle multicast-related conspiracy among server, switches, Android, and the Mono network stack that Roon uses. In my case, neither turning off power management nor turning off IGMP snooping did anything for several different Android devices last year. But now, turning off IGMP snooping is reproducibly enough to fix the problem. In the meanwhile, all the software and firmware involved has changed, so who knows what constellation of factors was responsible for the persistent failure last year…
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In my case turning on the wireless in my Nuc Rock AND having a wired connection fixed the issue.
Excellent, glad that helped someone at least 
I can confirm that this problem has disappeared ever since I switched my Asus router with the Sky Q router. So I’m guessing it has to do with some advanced setting available on the Asus but not on the sky router.
Spoke too soon. Problem reappeared tonight.
Oh well. I’m sure Roon will sort it in the end.
Brian
D’oh! Sorry to hear that - worth a shot.
Further update: turning off IGMP snooping is working well not just for my Pixel 2 but also for an older Nexus 7 that I had not been able to connect to my core since Roon 1.4 (or even earlier).
I just disabled IGMP snooping on my Netgear switch and my Nexus 6P snapped right up. It has not worked in any usable fashion for a long time. We will see if it is stable …
It’s great that for the first time there seems to be a reproducible fix for this problem! I had heard over the years that multicast is a tangled mess, but until this I had not appreciated how tangled and messy it could be. It’s not as if the network stacks for NetGear, Linux, or Android are exotic, but this particular combination with Roon must be tickling an incompatibility that was not clearly recognized before.
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My network is based on a FritzBox from xs4all, plugged into the main Google WiFi, and with 3 more additional Google WiFis for the mesh network around the house.
According to Google’s product support forum, there is no IGMP snooping at all on their mesh network, so it seems that it’s very unlikely the reason why I get these issues on my Samsung S8 (but not on iOS and Mac OS devices) is not related to IGMP snooping.
From a lot of experimentation since the Android failure to connect showed up last year, my hunch is that this is a subtle multicast interaction between Android, routers/switches, and Core server. IGMP snooping on NetGear seems to be what tickles that problem in setups like mine, but I very much suspect the root cause is elsewhere, likely in one of more of the network stacks involved.
I had unmanaged switches and I still had problem with Roon and linux .
I now use windows and Mac and have no problems at all
in fact, i got rid of my sonictransporter, which is linux based and went to a fanless inexpensive
windows pc which works great.
Looks like this problem will persist for a long, long time. Worst, Roon has no idea where’s the problem. Maybe I should just move back to Windows version for Roon Server.
@mike After more than a week of perfect functioning, my Pixel 2 XL stopped talking to my Core just now. The Ubuntu NUC running Core has been up for 10 days, 4 hours, 03 minutes. Roon itself has been up since Feb 9. My Pixel was consistently talking to Core until 1/2 ago. Now, nothing, even reinstalling the app. My network hasn’t changed at all. Looks like IGMP snooping is not the only setting that tickles this problem in my current network. Update: I was looking at traffic and settings on my main router (Ubiquiti EdgeRouter PoE), so I checked for new firmware, found it, and installed it, which needed a router reboot and a corresponding WiFi AP reboot (since the AP is powered by the router with PoE). Guess what, my Pixel sees my core again! I doubt that this is anything thing to do with the new firmware, the changes are slight, but it looks like the network reboot allowed something somewhere to reset or time-out into a good state. This is so frustrating!
Same issue here (already reported a long time ago) with my Android tablet and phone (Xperia Z3 and Z5) - no connection problem with my Dell Windows 10 computer.
A restart of Roon server (installed on a QNAP TVS-471 NAS) always fixes the problem (connection to the core is immediate after restarting the Roon server). Then I can play music… but the connection is often lost again and the only way to stop the music is to stop Roon server.
In my room (where I do not use my computer, and don’t want to), the only solution I’ve found was to come back to Logitech Media Server. So I don’t use Roon anymore when I go to bed and want to listen to music before sleeping!
Hope that the Roon guys will eventually reach a solution to this very frustrating problem.
Thierry
Also stil having problem’s connecting from Samsung Galaxy Note4, as remote to NUC7i3DNKE running ROCK. Strangely enough Roonremote appears to be connecting to my Win10 workstation just fine, frustrating.