My application sends some UDP packets on a multicast address. In our office we have 3 subnets connected via routers. Sitting in my subnet I'm able to ping the IP of the other subnet.

Will multicast packets cross my subnet and reach the machines of other subnets? Or router will need some configuration? Or do I have to program a bridge for it?

Please note that I do not know anything about Networking. Kindly tell me something that I can ask my network admin to do.


The router will need to be configured to pass the packets. There's a variety of ways to accomplish this. The most common two are to pass all multicast addresses or to setup RSVP. RSVP requires routers and source applications that support it, so it's not usually used for smaller simple installs. In the case of smaller networks it's common to just configure the routers to pass all multicast packets.

  • Hi, what if there is no router? How could you multicast to the other subnets? – Gobliins Oct 15 '12 at 10:24
  • 1
    Sending pakcets from one subnet to another isn't possible without a router... So there's no way to make multicast, or any other IP, service available in that situation. – Chris S Oct 15 '12 at 14:38

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