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I have a single Multicast source which I would like -for testing purposes- to duplicate over several Multicast addresses, e.g.

an host sending packets to 239.0.0.1, I would like the same traffic to be sent over 239.0.0.2, ..., 239.0.0.N as well.

Is it possible by configuration at network level? I'm working with Cisco L3 Switches.

Thanks in advance for any suggestion.

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  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer.
    – Ron Maupin ♦
    Commented Aug 14, 2017 at 18:45

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A multicast group is a destination IP address on an IP packet. The destination IP address is determined by the sender, and modifying an IP address on a packet is called NAT (Network Address Translation). Cisco switches cannot do NAT, only the routers can. Also, NAT does not duplicate packets, it only modifies existing packets.

The point of multicast is that one packet is sent to multiple devices on a layer-2 LAN that listen to the same multicast group. If you have three devices that listen to three different multicast groups, your multicast source needs to send a packet to each multicast group.

You do not solve this problem with network devices, but with the multicast source or receivers.

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  • I know the issue. I wouldn't speak of NAT. Multicast helper, for example, is a feature that allows for converting broadcast to Multicast, and I don't think is related to NAT. I was wondering of something similar for converting Multicast to another Multicast (can helper be used?) or, but this sounds intricate, converting Multicast to broadcast and then converting broadcast to another Multicast.
    – kuma
    Commented May 19, 2017 at 12:46
  • If you change either the source or destination IP address on a packet, that, by definition, is NAT; you are translating a network address. The IP multicast helper used to transport broadcast across routers really is a form of NAT. You are wanting to replicate packets and NAT those packets.
    – Ron Maupin ♦
    Commented May 19, 2017 at 14:10

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