Question Broadcast port forwarding for WOL with a secondary DDWRT router

Apr 5, 2020
Hi guys,

so here is what I am trying to do, I would appreciate some advice, because I am not an expert in networking.

I am configuring WOL for my PC, so that can be waked from outside of local network. What I've learnt so far, that this requires broadcast port forwarding. I have a modem+router device ( from my ISP, which unfortunately doesn't support that. However, I have a secondary DD-WRT router ( configured, which I use for DDNS, because the ISP router does not support that either. On DD-WRT, the gateway and local DNS point to and is only used as DDNS updater, so all my devices (wired or wireless) are connected to the Internet through the ISP router - for speed reasons. The WAN port is not used on DD-WRT.

Because DD-WRT supports broadcast port forwarding, I thought that I could use that router for WOL as well. To do that, I disconnected my PC from the ISP router and connected to DD-WRT router (for this PC, bandwidth is not crucial), also set up the port forwarding for UDP port 7 to on DD-WRT.

What I have expected is, that now I can send WOL packets to the DDNS hostname (works), the DD-WRT router receives them and broadcasts them (fails). However, the packet is only received by the ISP router, which cannot broadcast unfortunately.

So, what can be wrong? The DDNS is configured on the DD-WRT router. Why doesn't it receive the package (or does it?) and broadcast?
It works on local network, if I send the package to

EDIT#1: Actually, it also works over Internet via DDNS. So if I port forward udp 7 on my ISP router to the local IP of my PC, then I can see the packets arrive in Wireshark. Of course it only proves that I can send WOL packets over DDNS address, because I need broadcasting, once I turn off my PC, and I cannot do that with the ISP router.

Thank you for your time and help!
If you need any more info about the configuration, please tell me!

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