Multicast Routing Question



  • Hi all,

    I have been experimenting with the pimd multicast routing package on my pfSense. I think I have fairly good handle on how igmp traffic moves between different LAN interfaces on my network, but I'm a bit unclear how it works if the multicast source is an address on the public internet i.e. not in the RFC 1918 address space. To be more specific, on one of my subnets I have an STB (TV Set Top Box) from my ISP that is connecting to a multicast group in the 232.0.0.0/8 address space, so an SSM group:

    https://en.wikipedia.org/wiki/Source-specific_multicast

    For sources I see two public IP's from my ISP listed. This is not for IPTV so I assume this may be the ISP distributing regular TV guide updates via multicast. My question is, can this multicast traffic (from the source IP's from the ISP) even reach the TV STB that's NAT'd behind the firewall? Or does one have to create firewall rules for that?

    Thanks in advance for your help, I really appreciate it.



  • So I got a little bit further on this:

    If I use the igmp proxy package instead of pimd, with the upstream addresses being the two ISP addresses and 232.x.x.x multicast address, and dowstream address being the LAN subnet (that contains the STB) I can see the the ISP's IP connect to the 232.x.x.x multicast address on the pfSense WAN interface (after setting up the appropriate pass firewall rule). This leads me to believe that multicast is working.

    However, I'm not sure how to duplicate this same behavior using pimd. It seems straightforward if all I'm doing is multicast routing between local subnets, but how would it work when the WAN interface and NAT come into play? Do I have to setup some manual NAT forwarding rules? Can I configure pimd in such a way that multicast traffic reaching WAN will reach the STB on the LAN subnet?

    Thanks in advance any help you can provide, I really appreciate it.


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