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I need to send a packet to more than one reciever (lets say 30). Assume I don't care that some of them do not receive it now (Application Layer will handle this). Now my solution is to use multicast, such that I send one time and each device in the multicast group receives one time(or tries to).

My Question is : Does the router forward the IP packet when it receives it? I could not find the answer to this on the Internet. The thing is all devices (senders/recievers in the multicast group) are connected to the same router, hence they are in the same network. The trick however is that a sender could be on the far right (geographically) of the network and one reciever could be on the far left. So it would make much sense if the router forwards it.

So how does the router handle this?

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    Your question is a bit confusing. Are the "devices" the multicast senders? Your question about the router depends on the type of router and how it's configured. You should also know that multicast is handled poorly on wireless networks. It's best to avoid it if possible. – Ron Trunk Dec 1 '16 at 13:24
  • Yes, the devices are the multicast senders. They are also the receivers as well. Their role keep switching from senders to receivers. I am not sure if multicast is the right approach though. Maybe broadcasting ? If yes will the router forward the broadcast packet? – M.C. Dec 1 '16 at 13:29
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Depending on how the access point is configured, it can forward multicast packets. Since they are a broadcast at layer 2, the access point will broadcast the packet at the slowest mandatory rate. That may impact your network performance. Note that the access point may or may not have a router built into it. Most commercial devices do not.

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  • So If I want to ensure delivery and ensure it in a fastest rate. I should use boradcast instead? – M.C. Dec 1 '16 at 13:40
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    No, broadcasts are always sent at the lowest mandatory rate. Otherwise, there may be a client who can't hear it. If you are close to the AP, you can send at 22 Mb, but another client further away may only be connected at 12 Mb. So the AP has to send the packet at 12 Mb so that everyone can hear it. – Ron Trunk Dec 1 '16 at 13:45

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