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Router / NAT Problem – Multicast

This topic contains 2 replies, has 3 voices, and was last updated by  stretch 9 years, 7 months ago.

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    I’ve got a bit of a complicated NAT setup that seems to be causing some problems for my Firefly clients. My outer most router (DD-WRT v23sp2, 192.168.1.*) has my server (Hardy running @ on it. Everything (rhythmbox / itunes) works just fine when I’m set up as a client of that router. Problem is I’m not typically a client of that router directly. Instead I have a second router (DD-WRT v24sp1, 192.168.2.*) as a client of the outer router to which I am normally connected.

    When I’m connected, either wired or wirelessly, to my inner router (192.168.2.*, ie i’d be something like I can’t auto discover my Firefly server. If I manually add the server ( to Rhythmbox on my laptop it works just fine. This suggest that the auto-discovery is dieing at the NAT.

    So I’m trying to figure out how to make this work automagicly. Can someone suggest a solution? Failing someone knowing how to fix the problem could someone at least tell me if the clients go out searching or if the server sends a broadcast for anyone around to pickup on?


    After a bit more research it looks like I’m running into a problem with multicasting, as such anyone who’s really up on the details of how this magic happens I’d really appreciate your help. I have checked this whole setup over wire and it’s clear that this is not a limitation of my wireless hardware. Just looks like multicast is killed at the router, so how do I get it across?



    Well, I have not thought this out in detail, so I may be way off. On the other hand, no one else is answering.

    There are a number of threads around here on aspects of this problem, have you done a search on them?

    What’s happening to you seems normal to me. Unless you have a specific address in mind, traffic on a subnet is going to stay on that subnet. Broadcast traffic is definitely going to stay on that subnet.

    On the network where I work, we have a number of udp broadcasts that we need to send to multiple subnets. The only thing that we have found that will do this is a program called udp-broadcast-relay. I don’t know it this will solve your problem, but it might work if you modified it. See this website:

    Why the two subnets? This might defeat whatever you are trying to do, but if you changed the netmask on both subnets from to, it might work. Of course, you won’t have two subnets anymore.



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