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So I have a swisscom router at home (not sure which model). Behind the router I got my homeserver which runs some services like teamspeak, ...

I noticed inside the router settings page that there are a lot of invalid port forwarding entries, and they increase with around 2 or 3 per day. I have no idea how they are able to "appear" out of nowhere on the router's config. Also the router crashes every time I make a change to the port forwarding settings, as it can't handle all that invalid entries (there are around several hundred invalid entries).

Does anyone know where those entries come from? I can reset the router to factory settings to remove them, but I need to know why those entries are getting added

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2 Answers 2

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Possibly a broken UPnP?

Try disabling UPnP on the router and see if that helps.

If it does, there are two possibilities:

  1. UPnP is broken on the router side, while clients are doing things correctly.

    Not much you can do here except trying to update the firmware to see if it's fixed. If it's not, you may have to disable UPnP as the only solution.

  2. There is a misbehaving UPnP client, and the router does not handle it well.

    You could try sniffing UPnP traffic to see what tries to add those port forward entries. Use Wireshark and listen for UDP traffic to port 1900, this will at least give you an idea. There may be easier ways to debug UPnP on the network, but I can't readily come up with any.

As Darius noted, if disabling UPnP on the router helps, the simplest solution is to just keep it off. That will mean no software will be able to forward ports automatically, and also will cripple device discovery / DLNA on your network (in case you use media streaming and such).

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  • Or just disable UPNP on the router completely if you are sure you are not using it.
    – Darius
    Commented Oct 1, 2014 at 9:19
  • @Darius UPnP is silently used by a lot of things; hard to predict when you will need it. Disabling is a drastic measure.
    – Xan
    Commented Oct 1, 2014 at 9:19
  • Hence why I was saying disable it if you are sure you are not using it. I made sure all devices in my home network does not use UPNP. Some devices have option to want to use it (or advertise things on the home network using UPNP), and I turn them off. So yes this may not work for OP, but it is an option to avoid future crashes. Besides any client needing to use UPNP will usually complain, and provide "how to do it manually" option.
    – Darius
    Commented Oct 1, 2014 at 9:21
  • Thanks, will check that out as soon as I get some time at home, may get tomrow or so till I can check
    – RononDex
    Commented Oct 1, 2014 at 9:26
  • @Xan what could UPnP be used for in my envoirement? We got several windows 8 clients, a 2 mac osx and 1 windows 2012 server, a network NAS and a network printer. I will try to update the firmware first. If that doesnt fix it I will try to turn UPnP off
    – RononDex
    Commented Oct 1, 2014 at 9:46
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After a technician from the provider (Swisscom) came to check the router, it turned out, that the router was damaged.

After replacing it with a new one of the same model this issue was gone.

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