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fegauthier
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Routing Multicast through GRE Tunnel

Wed May 04, 2022 12:02 am

Hi guys!

I want to route multicast traffic from Site A to Site B via a GRE Tunnel.

I already setup the GRE Tunnel between the two sites and it's working well.

I saw that I need to use PIM-SM to forward Multicast traffic through the GRE Tunnel. I don't find any example on how to do that.

Site A has a DHCP interface that provide multicast. I want to forward this traffic through GRE Tunnel (172.168.0.1)

Does anyone can show me how I can achieve that?

Thanks
 
tangent
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Re: Routing Multicast through GRE Tunnel

Wed May 04, 2022 2:03 am

I don't find any example on how to do that.

There’s a detailed article on it in the old docs. As with much else, this topic hasn’t yet made it into the new docs. Always search both before resorting to alternate sources.
 
fegauthier
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Re: Routing Multicast through GRE Tunnel

Wed May 04, 2022 2:44 pm

Thanks for your reply!

I did read the post you linked but I'm actually new with multicasting and I don't understand everything about it. Do you know how should I configure PIM-SM to send the Multicast traffic from sender to the receiver? Below, there is a schema of my configuration.

Image

On Router A side, I actually use IMGP Proxy for devices to be able to join multicast and it works fine. On Router B, unicast traffic flow well but not multicast at all.

Can you help me?
 
tangent
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Re: Routing Multicast through GRE Tunnel

Wed May 04, 2022 3:43 pm

Image

That's pretty much the example at the bottom of the article. The only mysterious and configurable part specific to your case is:

/routing pim rp add address=172.16.0.2
 
fegauthier
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Re: Routing Multicast through GRE Tunnel

Wed May 04, 2022 4:08 pm

In RouterOS V7.2 PIM doesn't exist anymore. It's replace by PIM-SM. I guess that I need to create an instance. Add all interfaces to this instances and add a static RP to 172.16.0.2 ? Did I understand well?
 
tangent
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Re: Routing Multicast through GRE Tunnel

Wed May 04, 2022 6:22 pm

I don't have PIM-SM running anywhere, either on RouterOS 6 or 7. I merely have a working knowledge of what it's for and how to configure it. This looks plausible under ROS 7, though it is untested:

/routing pimsm instance
add name=pimsm-instance-1
/routing pimsm static-rp
add address=172.16.0.2 group=239.255.0.0/16 instance=pimsm-instance-1
 
tangent
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Re: Routing Multicast through GRE Tunnel

Thu May 05, 2022 3:57 am

In RouterOS V7.2 PIM doesn't exist anymore.

There's a thread claiming that PIM-SM doesn't work right, but it is supposed to exist. My example is simpler than the one in that thread, though, so perhaps it will work where that one doesn't.

If my attempt also doesn't work, I recommend that you report that to support, if only to let them know there are people who care that PIM-SM works properly. I don't do it for you because my uses of multicast are on a flat LAN, so I have no standing in the matter.

It's replace by PIM-SM.

No. PIM's Sparse Mode (SM) is the only mode RouterOS has ever supported. The only thing that changed in this regard is that "/routing pim" is now called "/routing/pimsm", though you can still get to it with "/routing pim" by making use of the v6 naming compatibility and abbreviation features.

What actually changed is everything in my command below that level, which is part of the big routing redesign in v7. They just haven't gotten around to documenting this aspect of the change yet.

The open question is if, in all this redesign, they broke PIM as claimed in that other thread.

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