NAS Service keeps disconnecting

@flatlander3​ I have it connected with 2 Ethernet cables. It's stock, plug and play. I haven't messed with any of its settings.

The IPv6 is set to "Auto-Configuration (Stateless)", the IPv4 is set to "Obtain IP address settings automatically via DHCP". The MTU is set to 1500.

I'm tech savvy, but don't know much about networks.

@kodiak79​ I'm not sure that 2nd Ethernet cable is going to help you out any and could really cause some issues if it's trying to do link aggregation or LAGG (I didn't look at your manual for that part).   Try one cable for now.  That will force a single IP address, but it should be fine.  That will get you roughly ~950+ Mbps throughput, which should cover most stuff fine.  Plenty for the multi-media stuff too.  Xfinity gear doesn't do LAGG anyway and it is a potential confusion point for services if your NAS tries to do it.  Your Xfinity gear is extremely limited. 

Also Stateless probably isn't going to work -- that's SLAAC, which probably isn't going to fly with how the RA announcements have to work with Xfinity (at least according to my debugging running a proper firewall) so on the rebind/renew, routing is going to get wrapped around the axle.  Just do the disable option (disable IPV6).  I'm not sure your gear has a correct setting that will work.  You really don't need IPV6 on an internal NAS device.  It's not going to buy you anything.  There's no performance increase or anything like that.  

Everything else on your network will happily speak to your NAS using IPV4.  Windows however does need IPV6 enabled, so don't disable the protocol on windows.  Windows will figure it out, and it is actually a required internal component now for a lot of windows internal services even if IPV6 doesn't entirely work or not properly on the network it is on.

Try it for a test.  See if you still have issues with your vanishing/stuck NAS.

Looking, the second Ethernet under settings says disconnected, only 1 of them is connected.

I'll pull the one, and disable the IPv6. I'll let you know if that works.

@flatlander3​ So, I unplugged second ethernet cable, disabled IPv6, and rebooted. Had to reset the Qnap to reconnect to it. I tried doing it again, and turned it off completely. Same thing, had to reset the Qnap to reconnect. I deleted it from the Xfi, rebooted again, same thing, had to reset the Qnap to reconnect to it. I rebooted the Xfi, same thing, had to reset the Qnap to reconnect to it. 

The IP address, isn't even changing. It's a 10.0.0.### IP address. Not sure if that matters.

@kodiak79​ Bummer.  So if the Lan tips over for whatever reason, if the connection flakes or the gateway reboots, your NAS dies?

You can verify that by just pulling the cable and plugging it back in.  Do you have to reset it for a temporary network error condition like that?  Does it have any error logs you can check out?  Try to figure out if there is any error recover it attempts...eventually?  I haven't worked with that one. 

Usually don't like canned NAS devices and just make my own.

* Edit:  OR is this thing going through some kind of error recovery or RAID rebuild from unclean shutdowns/resets all the time?  Stomping on it with a power button or reset is usually not a good thing to do to a RAID.  You really want to do that from an interface.  Usually, you want stable power and a UPS for something like that too.  In any case, I'd check out log files on it it.  Perhaps you'll see some warnings about unclean file systems.  RAID rebuild/restripe can take quite some time.