Synology DS416play drops off network once a week

I have a Synology DS416play, just turned four years old, that drops off the network once a week. It started doing this about four months ago. The machine still appears to be running (power light on), but I have to do a forced shutdown and restart to get things back to normal. Not something I like to do to computers. The Synology is plugged via Ethernet directly into a FiOS router.

Obviously, something changed. Perhaps a DSM update or something. I always access the NAS from my Mac Book Pro every day when I am on the same network; which of course is not every day. The NAS is not exposed to the Internet; just local.

I have no clue why this is happening.

Anything in the logs?
(You might need to install Log Center to get more detail.)

It is always at the day and time or randomly about every week?

@JohnAtl nothing in the logs about the network disconnect. The only non-ordinary log entries are when I force a shutdown and then restart.

@MacExpert I cannot say what time of day these occur because I never notice it until later, and there is no “network disconnected” log entry … it just occurs every 6, 7 or 8 days. I cannot pin it to a given external event like a network outage (there are none) or a job writing to the NAS (these always finish without error).

I’m blaming it on DSM with no proof, of course. But the NAS hummed along for years without loss of connectivity until four months ago. I keep all installed packages up to date, manually, so I suppose a package update could have caused this.

Can you still ping it?

Did you assign a static IP address to it?

@MacExpert – yes, I had set aside a static lease for the Synology device. I notice however that I had configured the NAS to get its address via DHCP. I’ll change that configuration on the NAS to used the fixed address.

Another thing I notice. I do not have IPv6 active on the FiOS router – no particular reason why not. I’ve just never turned it on. Should I?

The NAS however is configured “Auto” for IPv6 setup. I assume that is the base out-of-box configuration, but I wonder if I should change that to off.

Yeah disable IPv6 or use for Local link only

I was having an issue with Big Sur on both iMac and MacBook and Synology NAS accessing shares when coming out of sleep. HTTP access worked ok. Posted here and eventually with great help got it going better. Not 100% (other factors maybe involved … dunno) with a drop or two each month–fixed by re-boot of Mac. Sometimes I power off/on the router to fix.

See Reconnecting to Synology NAS After "sleep" seems impossible : Fixed - #14 by csf111

So, if I understand correctly, you suggest disabling IGMP routing on the Fios router?

It is on, now, and must be the default because I have no record of setting it to on.

I hesitate to turn it off for two reasons: I have no idea what the effect of turning it off would be on everything going on with the local network; and I don’t quite understand why it would affect the Mac-NAS connectivity.

(You do however make me wonder if the issue is not the NAS losing its network connection, but the Mac losing its connection to the NAS. I’ll have to monitor that for a while.)

To be honest, I don’t know. An IGMP could hit me and I wouldn’t know! I have rudimentary knowledge of TCP/IP networking learned in the early 1980’s and haven’t been able (or interested) to keep up with it.

All I know is what @csf111 explained and I put into my “close out report”.

My two bits:

  • what’s the worst that could happen if you turn it off? Or on? Could you really tell difference? For me things seemed to get better so I went with it.

  • I also concluded it’s the Mac OSX that is flakey here. But probably a far edge case that may or may not ever get fixed.

As far as I know an IGMP is an independently glorious member of Parliament. But I could be wrong.

I think I’ll hold your suggestion on the back burner for a while until I see if the other changes I made this week have an effect. If the weekly problem does not occur for a while then I’ll explore the IGMP option. I’m hesitant to turn off something that Verizon turned off by default since I have a lot of home automation hanging off my local mesh.


I have a question regarding what you are seeing. When you say the Synology “drops off the network”, do you mean it is completely inaccessible or just not available via Bonjour discovery?

Put another way, suppose your Synology host name is “fred.” If you try to access it via the DNS name “fred.local” do you find that the host cannot be found, where as if you access it via its assigned IP address (whether DHCP or static) then it is accessible?

If so, then the problem is likely with avahi, the Linux based daemon that handles Bonjour (or ZeroConf as it is called in the non-Apple world). As best as I can figure out, avahi has a problem when IPV6 is enabled that causes it to stop working periodically.

I have had the same problem and found it started a number of months ago after a Synology OS update, presumptively either enabling IPV6 on the Synology or installing an updated avahi which has this failure.

If I log in to the Synology via a shell (eg SSH) and kill avahi, it will automatically restart and functionality will be restored for a period of time, at least until avahi dies again.

I have found a number of references to this problem via The Google.

For me, I can’t find a process by that name using Mac’s “Activity Monitor”. What is the process name (in case different) and what command do you issue to restart it. I’m happy to give it a try in the once/twice a month the connection to [hostname].local can’t be found. Far as I know, I’ve not enabled IPV6 on NAS or Mac.

What I documented as helping my situation was when I was seeing it fail many times a week. So things did get better.

This process is running on the Synology, providing ZeroConf services for the Synology. You will not find it on the Mac.

On the Synology, when connected via a shell, you can use:
ps aux | grep avahi
to find the process and get its PID, then use
kill -9 <PID>
to kill the avahi process after which it will automatically restart.

thanks. i’ll take note and when connection lost, i’ll try that. (Till now I’ve been re-booting Mac to restore the connection, for what it’s worth … haven’t rebooted the NAS for a long time)

Thanks for posting.

The Synology appears to be running (green light; disks spinning) but it is not accessible via laptops or iPads. That’s what I called, colloquially, “drops off the network”.

As I mentioned, I’ve made some changes suggested by @MacExpert, and now I want to monitor for a few weeks.

If anything, I’ve learned from this problem and the excellent help from others in this forum, that networking troubleshooting is (a) more obscure than Finnegan’s Wake; (b) there are thirty-five possible root causes and forty-two valid solutions for each root cause when there is a NAS issue. :slight_smile:

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@rms: I think your issue is different from that of the OP, so I am not sure that restarting avahi on the Synology will help you, but it will be interesting to find out.

@anon41602260: I am curious to know. When you say not accessible, what specifically happens?

For example, if you try to ssh to “synologyname.local” do you get a “host not found” error, or does the name translate to the correct IP address but the connection times out?