# Multicast routing without igmp



## jgreco (Oct 21, 2011)

So I guess it's cool that new TV's come with "Internet" and we now have smartphones that also talk Internet, but boy, it seems to all be dodgy.

I've got a Samsung TV, and the iPhone "Samsung Remote" app.  They use SSDP (239.255.255.250) on multicast to identify each other.  This works - if they're on the same net.

Well, our iDevices and our media devices are on different networks here, because there are different access policies and resources that they need access to.  But this is all multicast, so it *should* be able to work.

The routers are configured for multicast, and mrouted's running.

Running "Samsung Remote" on the iDevice, an entry for the IP of the iDevice is entered into the "IPv4 Multicast Forwarding Table" on the router (as seen by netstat -g) as one would expect.

But the TV never appears.  Digging.  So it appears that the TV never sends an igmp message to become part of the group.  @*# ????  I'm not even sure how that can work at the switching level, do switches just broadcast mcast packets when no igmp has specified a group?

So I am wondering if anyone has any suggestions (and putting them all on the same network is a nonstarter, so don't bother with it).  I also don't expect to get any satisfaction from Samsung support; they'll almost certainly say "two networks is not supported." 

I can't figure out if there's a way to manually add a multicast group membership on a FreeBSD router without the device asking for it.  Probably is if I write some code, but just looking for ideas in the meantime.

Thanks.


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## jtom (Jan 10, 2012)

Usually when you open an app who uses multicast, the app automatically joins the configured multicast group
You could play with VLC for example but you need to do it on the same LAN segment otherwise it wont work (unless some multicast routing protocol is enabled by your ISP)


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## SirDice (Jan 10, 2012)

jgreco said:
			
		

> I've got a Samsung TV, and the iPhone "Samsung Remote" app.  They use SSDP (239.255.255.250) on multicast to identify each other.  This works - if they're on the same net.


I'm guessing it also uses UPnP on UDP port 1900. 
http://en.wikipedia.org/wiki/Universal_Plug_and_Play#Discovery


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