How to allow multicast packets get to my CentOS guest, over NAT?

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How to allow multicast packets get to my CentOS guest, over NAT?

Postby davis8988 » 11. Jun 2019, 18:02

Hello,
Is there a way my CentOS guest can receive multicast packets when configured with network: 'NAT ' ? (not 'NAT Network')

Host: Windows 7
Guest: CentOS Linux release 7.5.1804 (Core)
Network: NAT
VirtualBox: 5.2.20

My windows host is receiving all these multicast packets with specified port, and I configured the port-forwarding settings to pass the same port to the guest machine. But still when I run
tcpdump
I don't see any packets.


How can I have my guest receive multicast packets over NAT?
davis8988
 
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Re: How to allow multicast packets get to my CentOS guest, over NAT?

Postby mpack » 11. Jun 2019, 18:43

Quick answer: no. At least not to my knowledge. If you port forward then the host loses the use of those ports, so this cannot be used to extend a multicast protocol.

Anyway, are you sure that "multicast" is TCP and not UDP? AFAIK TCP doesn't support multicast, and a tcp dump (I assume) will not see UDP packets.

The best solution, if possible, would be to use bridged networking instead of NAT.
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Re: How to allow multicast packets get to my CentOS guest, over NAT?

Postby davis8988 » 27. Aug 2019, 18:29

Hi,
Thanks for your answer. You are right the command I later found out to help me catch udp packets is:
Code: Select all   Expand viewCollapse view
tcpdump -i lo udp

I ended up bridging anyway.
davis8988
 
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Re: How to allow multicast packets get to my CentOS guest, over NAT?

Postby fth0 » 28. Aug 2019, 01:48

Despite its name, tcpdump captures any network traffic (like Wireshark). It's typically pre-installed on most Unix OSs (Linux, macOS, xBSD).
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