DLNA and Router UPnP

[cbkihong]

There were a long-standing issue at home that my DLNA clients frequently lost connectivity with the DLNA servers. One of the DLNA servers is a NAS in which I place media files to be served over DLNA to TV, desktop and mobile etc. I did a tcpdump on the NAS and saw the NOTIFY messages to UPnP multicast as expected, but another Wireshark running on the desktop nearly never saw those multicast messages, and I confirmed that at that time there were no DLNA servers discovered by my other DLNA clients.

I noticed that there is an "Enable UPnP" option in the ASUS RT-AC87U router I use at home, which I previously set to disabled. I enabled it, and voila, I saw the multicast messages on my desktop and had no problem with DLNA browsing since.

My understanding is the disabling of UPnP at router is mostly a security consideration. I did a port scan test at GRC and apparently the router didn't respond to upnp on WAN, even though I switched upnp to enabled. Seems good.

So my questions.

1. Am I doing the right thing? So my expectation is the router should not have blocked the upnp related multicast messages in the LAN, so what I wanted to do is just to unblock it inside the LAN but NOT WAN. If I was doing the wrong thing, are there other approaches that allows me to achieve this without enabling UPnP at router?

2. What does that option do actually? For my use case, i.e. DLNA, I do not see directly why support from the router would be needed. All I see is that it looks like the DLNA devices go through some discovery messages over the LAN and then the rest are direct connections between them. Or did I misunderstand something?

Thanks!

 

[ColinTaylor]

I noticed that there is an "Enable UPnP" option in the ASUS RT-AC87U router I use at home, which I previously set to disabled. I enabled it, and voila, I saw the multicast messages on my desktop and had no problem with DLNA browsing since.

Are you referring to the "Enable UPnP Media Server" (USB application) option or "Enable UPnP" (WAN)? The later has absolutely nothing to do with DLNA despite the similar names. All that does is allow applications to create port forwarding rules in the firewall.

The increase in multicast traffic is probably just Windows using SSDP to discover the new service that's now running on the network.

 

[cbkihong]

The latter. I am not familiar with multicast, but should these messages from the NAS expected to be seen by DLNA clients? After I disabled UPnP (WAN), the DLNA client no longer see these. And DLNA browsing no longer works after making the change and rebooting the router.

00:02:48.104093 IP 192.168.1.21.46745 > 239.255.255.250.1900: UDP, length 504
E...^.@...dz...........l....NOTIFY * HTTP/1.1
HOST: 239.255.255.250:1900
CACHE-CONTROL: max-age=180
LOCATION: http://192.168.1.21:50001/desc/device.xml
OPT: "http://schemas.upnp.org/upnp/1/0/"; ns=01
01-NLS: 7ba9abf2-ed79-11e7-abbe-fc0dd278ece6
NT: urn:microsoft.com:service:X_MS_MediaReceiverRegistrar:1
NTS: ssdp:alive
SERVER: Linux/3.10.102, UPnP/1.0, Portable SDK for UPnP devices/1.6.21
X-User-Agent: redsonic
USN: uuid:00113210-6757-0011-5767-576710321100::urn:microsoft.com:service:X_MS_MediaReceiverRegistrar:1

P.S. This is captured on the NAS (DLNA server).

 

[ColinTaylor]

I can't think of a reason why UPnP (WAN) being enabled would have any effect on DLNA traffic, or any other LAN traffic for that matter. Unless it's some sort of bug where the effect is coincidental. Are the client devices connected wirelessly? Do you have the same problem when both the client and the server are connected by cable to the same switch?

EDIT: I've realised that your router has the troubled Quantenna chipset for the 5GHz radio. It would be interesting to know whether the problem is restricted to 5GHz clients.

Check the IGMP snooping settings (under LAN > IPTV and Wireless > Professional) as they do effect multicast traffic.

 

[cbkihong]

The pair I talked about (NAS / desktop) are connected by LAN ports directly on the ASUS. Not even wireless but the issue affected devices regardless of being on wired or wireless.

I assumed your suggested setting affect wireless only, so if in my case I have issue on wired LAN as well, I can safely consider that irrelevant to my use case?

 

[ColinTaylor]

Yes most of the ideas were about wireless problems. But it would still be worth experimenting with the multicast settings at LAN > IPTV as that has been known to have expected effects on LAN traffic.

 

[cbkihong]

OK, thanks. I have just disabled UPnP (WAN) at router and enabled "enable multicast routing (IGMP proxy)" on IPTV page and rebooted router. For now DLNA seems to be still working but I will see if the problem comes back later.