How to debug a DLNA infrastructure?

Question

I am stuck with a peculiar situation at home, and would appreciate any help.

I have:

• Marantz NR1504 AV receiver, connected via PowerLan and Ethernet to the router/modem.
• Samsung SmartTV, connected via WiFi to the same router.
• Android smartphones, with BubbleUPnP, connected via WiFi to the same router.
• Synology DS414 connected via Ethernet directly to the same router.

Synology carries a collection of musical files, MP3 and FLAC. I could access this collection from the TV, the receiver and BubbleUPnP. I could play them directly from the receiver, play them using the TV using HDMI-returned sound, or use my smartphone to access the musical collection and play the sound with the receiver.

Synology serves the musical files using Media Server.

To summarise, the situation was like this:

• BubbpleUPnP could see the musical collection on Synology and could see the receiver.
• Receiver could see the musical collection on Synology and could see the BubbleUPnP.
• TV could see the musical collection on Synology.

Everything worked fine, until some moment. I didn't use all features all the time, so I don't know when exactly things went wrong. However currently the situation is like this:

• BubbleUPnP does not see Synology at all; it still sees the receiver.
• Receiver does not see Synology at all. It does see BubbleUPnP.
• TV can see Synology just fine, with all media files.
• Synology's Media Server shows TV, BubbleUPnP and receiver in Media Server > DMA Compatibility > Device List.

So:

• Two DLNA channels work just fine: TV—Synology and BubbleUPnP—receiver.
• Two DLNA channels work one way: Synology sees BubbleUPnP and receiver, but not the other way round.

I wonder if there is a "standard" or recommended approach to debugging such configuration. Since it involves multiple vendors and devices and a rather complex network configuration, I wouldn't even know which technical support to ask. On the other hand, I believe there should be some knowledge in solving this kind of issues, and that's what I am looking for.

Answer 1

These problems are always tricky to figure out. The approach I take is to first document each network interface on each device, including routers, access points, and POWERlan adapters. Record the MAC address, IP address, default gateway, netmask, and hostname.

Now, go to your main DHCP server (probably in your home router) and make sure its logs show the exact same MAC addresses you recorded, and that each MAC was issued the exact same IP addresses you saw. A difference may mean you've accidentally enabled a second DHCP server (perhaps hidden in a cheap access point, WiFi range extender, or POWERlan adapter) which could be creating false network settings in some of your devices, slicing your network in two.

Make sure all your devices are in the same subnet. That means they all have the same netmask, and the topmost bits are all the same as each other. For example, if your router's netmask is 255.255.255.0, then all your devices should have their top 3 octets in common with the default gateway and each other, such as 192.168.1.1, 192.168.1.2, and 192.168.1.3

In a small home network such as you've described, I'd expect all devices to share a common default gateway. Make sure it's the internal network facing IP address of your router.

If you think it may be a rogue DHCP problem but just can't figure out what's going on, consider converting all your network interfaces to use static IP addresses.