udp multicast stream blocks internet

[ColdFireIce]

Hi,

I've tried to solve this problem on my own, but I'm stuck.
I have a setup, where I want to stream audio/video from a server (192.168.0.5) to multiple clients (192.168.0.x) in an class-C LAN.
The network is connected to the internet by a router (192.168.0.1) all standard so far.
Now if I start a unicast upd/rtp stream on the server with a single IP address, everything works fine. But if I use a multicast address the stream is still reachable from the clients, but I can't connect to the internet or the router anymore.
I tried the normal broadcast addresses from 224.0.0.0 - 239.255.255.255 as also the subnet broadcast 192.168.0.255 on both ways the stream works, but on both ways the router seems to be blocked.

everything is connected via an Netgear GS108 GE, the router is a Netgear WGR614v7

I hope someone can help me, and point out my error.

Greatings

[Rémi Denis-Courmont]

Make sure the network segment does not include WiFi. Multicast does not work over WiFi (except for some rare professional-grade access points).

If there is no WiFi, and it still does not work, then that's most certainly a bug in the router. Not much room to help you then.

[ColdFireIce]

hmm,

thanks for the quick answer. Wich Multicast address is actualy the right one in my case. I couldn't find any information on this topic. 224.0.0.0 - 239.255.255.255 or 192.168.0.255

Greatings

[cbscpe]

Hi ColdFireIce,

I suppose you are using a cheap Fast or Gigabit Ethernet Switch to connect all your stations with the server and the router. Now when you use a multicast IPv4 destination the switch has no other solution than to forward the multicast packets to all ports on the switch, whether the device connected to that port is interested in those packets or not. Now depending on the type and model of the internet router he will be completely overloaded with this IPv4 multicast traffic and hence seems to be dead. What you need is a switch that supports dynamic multicast filtering. Mostly this is based on IGMP snooping, but for this to work you need also to have a IGMP Querier on your LAN that takes care of querying all stations and all stations should use the same version (typical v2) of IGMP. You could also try to block multicast from the router port, but the switch needs to support that (i.e. needs to be configurable).

As for the multicast IP Address to use: As long as you have not activated IPv4 multicast routing on your router (and most low-end routers don't even support this) they will not reach the internet. However IPv4 Multicast has been devided into special ranges and scopes. E.g. the Range 224.0.0.0/24 has been assigned as link-local multicast addresses, those packets will never be forwarded by a router. The Range 239.0.0.0/8 has been reserved as privat range (local scope) like the 10.0.0.0/8 range for privat addressing and will never be forwarded in the Internet. Typicall DVB streaming examples use the 239.255.0.0/16 range and that's what I'm using as well.

Regards

Peter