Issues with Multicast Routing

sergio-tota · 2017-11-03T21:16:53.000Z

Hi,

I have a GL-AR300M with the latest version of the firmware.

I am using it with OpenVPN to connect to a OpenVPN server and everything works fine except multicast (SSDP) traffic which, at the moment, is NOT routed to the tun0 interface and I don’t understand why.

The devices connected to the br-lan interface(s) do generate UDP SSDP multicast traffic using port 1900 and destination address 239.255.255.250.

If I dump the traffic at the br-lan interface with tcpdump I do see this traffic but if I dump the traffic at the tun0 interface I don’t see any of this traffic anymore.

I have played with iptables to make sure that this type of traffic doesn’t get dropped and I have added a static routing rule as well but with no luck.

I have also installed scmroute to subscribe the br-lan to a multicast group but I still can’t see any multicast traffic being routed from br-lan to tun0.

Do you have any suggestions on how I can achieve that? As I said I would like to somehow add a routing/forwarding policy to route all the SSDP traffic generated by a specific IP and coming from the br-lan interface to the tun0 interface.

I already don’t understand why it is not happening after all the configurations I made but I’m clearly missing something.

Thanks in advance for your help.

Sergio

alzhao · 2017-11-04T13:50:13.000Z

Is SSDP data UDP? I think all TCP and UDP data should have been routed.

You can refer to /usr/bin/setvpnfirewall (cannot remember the name) for iptables rules.