UPnP/DLNA Frustration

[cpt_paranoia]

I've been running DLNA server and endpoints on my home network for a few years now. Whilst it has had its odd hiccups, it has mostly worked without issue.

However, I have recently changed ISP, and their supplied router seems to have broken it.

Sort of...

I have a Denon N5 that I have streamed to from my NAS without much trouble, driven by BubbleUPnP on my phone. It now appears and disappears at random in Bubble, even whilst playing.

The LMS UPnP bridge also sees it only intermittently.

And yet it seems to be visible/playable to MusicBee without problem.

May have to try an older copy of BubbleUPnP, to see if they've broken it in a recent update; the Denon hasn't updated for a long time, and is obviously working with MusicBee, so not having WiFi issues.

I swapped out the ISP router for an older one, with identical network and WiFi setup. All devices connected fine, and the UPnP/DLNA devices seemed to operate correctly. But it's an ADSL modem, and the line is now VDSL...

The ISP hasn't been helpful, in spite of their TV advertising suggesting their service goes beyond normal expectations (no, PlusNet, this won't do...). Their first line support refused to even discuss it, or suggest how I might take the issue further. It was only when I asked how to complain about the support operator that I got passed to second line service. Who admitted their supplied router wasn't very good...

If I could be confident a real router would solve the problem, I'd go and buy one. The sad thing is, most ISPs seem to buy modem/routers that are half decent, but then insist on having custom firmware that is neutered and broken, and doesn't seem to have even got past alpha testing.

The ironic bit is that I mostly use this at night, to relax me as I go to sleep. It's having the opposite effect at the moment.

Just venting, really, but if anyone has any bright ideas...

 

[cpt_paranoia]

Dug out a spare VDSL modem/router I picked up in a charity shop for 50p (TP-Link W9970), and managed to convince it to authenticate with my ISP. DLNA devices appeared immediately, and are happily playing.

Just need to figure out how to open up ports in the firewall. [edit: done; they do it as part of the port forwarding process]

Think this proves pretty conclusively that the ISP-supplied router is a piece of junk... Well, I think the hardware is fine; it's the custom, neutered firmware that's the problem. ISP routers seem to be pre-alpha release builds that rarely get updated. I wonder how much money they waste on customer support for this dross, and how many dissatisfied customers they lose... I guess they just don't care, as they know that the customer wil jump ship in 18 months anyway, due to their stupid pricing policies. Another junk router sent to WEEE...

 

[dewdude]

This activity should be local...so your router shouldnt have anything to do with it unless its so instable its killing your LAN.

 

[cpt_paranoia]

This activity should be local...so your router shouldnt have anything to do with it unless its so instable its killing your LAN.

A router is responsible for routing traffic within a local network.

It's not a coincidence that replacing the router immediately and permanently fixed the problem.

 

[dewdude]

A router is responsible for routing traffic within a local network.

Actually...it is not. A router is responsible for routing traffic BETWEEN networks. If all of my computers are connected to the same LAN and are all configured with the same network information; then there is no router required. So my PC at 192.168.1.191 can talk to 192.168.1.2 *without* the router getting involved. A router can provide SOME information about your local network...but it most certainty does NOT route traffic around your LAN.

Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0      192.168.1.1    192.168.1.191     25
        127.0.0.0        255.0.0.0         On-link         127.0.0.1    331
        127.0.0.1  255.255.255.255         On-link         127.0.0.1    331
  127.255.255.255  255.255.255.255         On-link         127.0.0.1    331
      192.168.1.0    255.255.255.0         On-link     192.168.1.191    281
    192.168.1.191  255.255.255.255         On-link     192.168.1.191    281
    192.168.1.255  255.255.255.255         On-link     192.168.1.191    281
     192.168.56.0    255.255.255.0         On-link      192.168.56.1    281
     192.168.56.1  255.255.255.255         On-link      192.168.56.1    281
   192.168.56.255  255.255.255.255         On-link      192.168.56.1    281
        224.0.0.0        240.0.0.0         On-link         127.0.0.1    331
        224.0.0.0        240.0.0.0         On-link      192.168.56.1    281
        224.0.0.0        240.0.0.0         On-link     192.168.1.191    281
  255.255.255.255  255.255.255.255         On-link         127.0.0.1    331
  255.255.255.255  255.255.255.255         On-link      192.168.56.1    281
  255.255.255.255  255.255.255.255         On-link     192.168.1.191    281
===========================================================================

This is the routing table for my laptop; it tells me exactly how traffic to specific destinations are to be routed. While the formatting is a little screwed up; notice how the majority of these list "On-Link" for the gateway. This indicates the traffic goes straight out to the network interface directly to the destination. So when I want to talk to 192.168.1.7, one of my linux servers on my network; the traffic goes DIRECTLY to the IP over the network. The only thing that uses my gateway (192.168.1.1) is the destination "0.0.0.0", which indicates "anything that doesn't match an existing route". We can see this by tracerouting.

C:\Users\Jay>tracert 192.168.1.7

Tracing route to 192.168.1.7 over a maximum of 30 hops

  1     1 ms    <1 ms    <1 ms  192.168.1.7

Trace complete.

At no time did my traffic go anywhere near my router. Since the LAN is all 192.168.1.0/24, it doesn't need to. Now...let's say I want to talk to my Synology.....which is technically on it's own LAN.

C:\Users\Jay>tracert 10.1.1.2

Tracing route to SYNOLOGY [10.1.1.2]
over a maximum of 30 hops:

  1     1 ms     1 ms     1 ms  192.168.1.1
  2     1 ms     1 ms     1 ms  192.168.1.253
  3     2 ms     1 ms     1 ms  SYNOLOGY [10.1.1.2]

Trace complete.

Now, in this case...it did go through my gateway...but only because I don't have a route for 10.1.1.0/24 programmed in to Windows (and probably why I'm seeing slowdowns talking to the synology). But noticed it sent it to 192.168.1.253. That machine is in fact "a router". In this case my PC did exactly what it was supposed to, sent the unknown destination to the router which then forwarded it to another router and on to the network. If I add a static route...things change.

PS C:\Windows\system32> route add 10.1.1.0 MASK 255.255.255.0 192.168.1.253
 OK!

Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0      192.168.1.1    192.168.1.191     25
         10.1.1.0    255.255.255.0    192.168.1.253    192.168.1.191     26

C:\Users\Jay>tracert 10.1.1.2

Tracing route to SYNOLOGY [10.1.1.2]
over a maximum of 30 hops:

  1     1 ms    <1 ms    <1 ms  192.168.1.253
  2    <1 ms    <1 ms    <1 ms  SYNOLOGY [10.1.1.2]

Trace complete.

Now the laptop isn't even bothering to talk to 192.168.1.1; it knows to go directly to 192.168.1.253 which will route it over to 10.1.1.0.

It's not a coincidence that replacing the router immediately and permanently fixed the problem.

The fact it did tells me something was really screwed up with your network configuration. Strictly speaking...you do not need a router to make computers on a local network talk to each other...only if you want them to talk to other networks.

Now what was screwed up...I don't know. It's possible your router could have been doing something screwy and hijacking all the LAN traffic, which is bad. Your systems could have been trying to use hostnames instead of IPs...which would have relied on your router to resolve them.

Just need to figure out how to open up ports in the firewall. [edit: done; they do it as part of the port forwarding process]

You should NEVER EVER EVER have to open ports on your main ISP router for local devices to talk to each other. An OS level firewall like iptables on linux or Windows Firewall...sure...those are filtering at the specific machine. But your local traffic should not be going through your router....and opening ports like that is just a stupid idea. You don't want people from the outside being able to access stuff.

 

[cpt_paranoia]

You should NEVER EVER EVER have to open ports on your main ISP router for local devices to talk to each other

I know.

They're not opened for internal traffic. They're opened for external access to services provided by devices on my local network.

 

[dewdude]

DNS is for that - @cpt_paranoia is right.

DNS is just name resolution.

 

[cpt_paranoia]

If all of my computers are connected to the same LAN and are all configured with the same network information; then there is no router required.

The box of tricks supplied by most ISPs these days is commonly* called a 'modem router'. It's called different things by different people, depending on how technical they are, and how closely they're adhering to the changing use of these terms (it's also called a 'residential gateway' by manufacturers and installers). Most will be wireless modem routers, too, providing a wireless access point. Most ISPs will drop the 'modem' bit, as it's confusing for customers, and just call it a wireless router; ISPs will rarely supply a pure router, because their business is selling internet access, which requires a modem.

This box of tricks will have a port to access the WAN, most commonly a DSL port, either ADSL or VDSL, or, for direct fibre to home, a fibre port. They will also have a number of ethernet ports, whether fast or gigabit. User devices can be connected to these ports. Since these ports are point-to-point with cat5 or cat6 twisted pair, rather than very old skool megabit ethernet that used a simple coax and CSMA to allow multiple devices on the same physical interface, all traffic flows into the router on its dedicated port, and out to the destination device on its dedicated port. In that sense, the traffic is passing through the router, and is being routed to the appropriate port. Similarly, Wifi traffic does not go source-destination over the air; it goes via the router's WAP from one Wifi device to another (unless it's using ad-hoc WiFi, or WiFi Direct, which would be unusual for a wireless router).

Yes, you can add ethernet switches that allow traffic to pass direct from one device to another, without needing to pass through the router. This is handy if the router only has FE ports, and you want to make use of GBE-capable devices on your network. An ethernet switch will learn what devices are connected to it, and pass traffic out to the appropriate port (unlike the old ethernet hub, which is a simple broadcasting repeater). Confusingly, 'hub' is now a commonly used term for the wireless router...

So, using the term 'router' as it is commonly used to describe the ISP-supplied box, plenty of local network traffic will pass through the 'router' (especially if no other ethernet switches are used within the local network, or one or both of the communicating devices is connected via WiFi). If, for whatever reason, the 'router' decides to muck about with that traffic, or fail to propagate packets correctly, various services can be disrupted.

One other aspect of ISP-supplied modem routers is that they are usually very limited in terms of user configuration settings, since most of their customers will want something simple, and the ISP doesn't want to have to provide the support to deal with people who have mucked about with settings they don't understand, and have broken things. The router my ISP supplied was exactly of this type; very few settings to adjust. An ISP-supplied router really should handle DLNA traffic out of the box. This router failed to provide robust DLNA operation, out of the box.

* There's nothing unusual about using the term 'router' to mean the box supplied by an ISP. Wiki and Cisco do this, too:

https://en.wikipedia.org/wiki/Wireless_router
https://www.cisco.com/c/en_uk/solut...ource-center/networking/what-is-a-router.html

Just in case this is UK parlance only, it looks like US industry also uses 'modem router' in this sense:

https://us.hitrontech.com/learn/the-difference-between-a-modem-and-a-router/

I hope that clarifies my use of the term 'router' in this context.

 

[gvl]

They're opened for external access to services provided by devices on my local network.

Sounds unsafe. @dewdude is of course correct, but it doesn't mean the ISP provided router is not junk as it can somehow cripple internal traffic although it would be highly unusual.

 

[cpt_paranoia]

Sounds unsafe.

That's a choice we have to make. Your firewall already allows traffic in and out of your local network; you couldn't access the internet without it.

Opening specific ports, and forwarding them to specific devices, and then to specific programs, allows some management of the risk. There's a reason why firewalls allow this sort of behaviour.

The thing that is much more unsafe is to allow UPnP control of the firewall; this allows a program to open up ports in your firewall without your knowledge. I'd always recommend people turn off that feature of their router. It's a different use of UPnP to the DLNA use, just to confuse things...

 

[gvl]

Your firewall already allows traffic in and out of your local network; you couldn't access the internet without it.

This is different. It only allows incoming traffic on an open TCP connection that was initiated from your internal network. For UDP yes in a sense, but those NAT holes are short lived in nature so generally deemed safe. By forwarding a port on the firewall you have a permanent security hole. Hackers will most certainly scan your external IP and find it. The device you are forwarding to may be running an outdated unpatched or mis-configured OS that attackers can exploit and gain access to other machines on your local network. It is a bad idea. If you must access your local devices from outside use VPN instead.

 

[cpt_paranoia]

I know what the risks are, thanks.

 

[dewdude]

The box of tricks supplied by most ISPs these days is commonly* called a 'modem router'. It's called different things by different people, depending on how technical they are, and how closely they're adhering to the changing use of these terms

Right...ok. I was beginning to wonder if a lot of the confusion was just due to the fact you were calling the all-in-one-black-box a router when it is in fact numerous things:

network router
network switch
wireless access point
firewall with NAT
DHCPD

If, for whatever reason, the 'router' decides to muck about with that traffic, or fail to propagate packets correctly, various services can be disrupted.

I guess it's possible the DHCP was configured to delete local rules and over-ride them with an "everything goes through me" bit. This is probably a major violation of standards...and in that case I'd disable the routers DHCPD and use my own. But most operating systems usually assume traffic with a destination on the local subnet goes out the interface by default. I guess I could try something that stupid with my stuff and see if Windows actually accepts it; but usually it'll reject invalid network configurations.

An ISP-supplied router really should handle DLNA traffic out of the box. This router failed to provide robust DLNA operation, out of the box.

Unless it was hijacking local routes....then again....it shouldn't matter. DLNA does not require anything from your router. Most of the time a router has DLNA options because it can act as a DLNA server; it usually has no bearing on if DLNA will work on your network.

This is also why I usually static out IPs on my network for critical devices and never rely on hostnames. In fact I run PiHole with recursive DNS....so none of my local devices resolve to a hostname anymore. I didn't feel like making DNSMasq work.

or, for direct fibre to home, a fibre port.

My FTTH box from Verizon doesn't have a fiber port on it; it has a dedicated gigabit WAN ethernet port, 4 gig ethernet ports, and a MoCA coax connection. The worst part about it is you can't disable UPnP due to the service provisioning of TV hardware. It has the simple idiot-proof interface...but I can still do things like get in to advanced menus and access it via SSH. I actually have a script that pulls the port forwards every hour to alert me to new UPnP set ports so I know what's going on. They did put the UPnP disable menu back in firmware...I'd tell you if it works but I don't have anything on my network requesting ports.