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JunOS very simple multicast routing (static)

  • 1.  JunOS very simple multicast routing (static)

    Posted 02-20-2023 13:09

    Hi all,

    I have a setup that requires me to forward (as in: route, not bridge) multicast traffic from one interface to another interface. The actual situation is a bit more complex, but this is the major hurdle I can't seem to take, so please help me.

    The traffic is organisation scoped packets (no real stream, just occasionally one packet), addresses like etc.

    The packets are sent by a PC that is connected to a L3 interface of a switch (EX3300). I can see the packets going out, but there is no easy way to check the switch interface (maybe a mirror port?) but it would be really strange if packets sent out on a p2p ethernet cable would not arrive at the switch interface it's connected to...

    Now I need these packets to be forwarded to another interface where they are picked up a firewall. At the moment, due to a JunOS bug, I cannot use subinterfaces for this, so the firewall is in a "p2p" vlan. The EX3300 has one of two ip's in vlan 16, interface vlan.16, the other is the firewall. Routing normal traffic is no problem at all, works like a charm. The default route also points to the firewall.

    How can I get JunOS to forward all non-local-scoped or specific multicast groups to be forwarded from an L3 interface (ge-0/0/26.0) to another one (vlan.13)? Believe me I have tried A LOT but it never happens. Including: igmp on/off on the interface, "multicast" interface on/off, I have been using pim-sparse and pim-dense (complemented with a service on the firewall), I tried to install static multicast routes, I've overriden "martian" configuration and combinations of all of them. 

    Once the traffic is on the firewall I will have the challenge to get the traffic back to the switch, but in another routing instance (vlan.19 (fw) to vlan.219(wireless)). That's where the clients live and that's where the joins happen. I'd like to cross that bridge once the first half is working, but that may not be possible.

    I'd be really grateful for a few tips on how to get started.

    NB: I've been using a similar but simpler setup, with only the firewall being the L3 point and that was working, so I know both the source as the sink can work. Also the TTL is not the problem ;-)

    Erik Slagter