We have the above LAB. All IP addresses are set, also the default route is sent on the Windows PC of the VLC Streaming Server.
I will go to the MikroTik Switch and create a bridge, then put Ether1/Ether2/Ether3 in that bridge. This is needed because the ports on MikroTik switches can work as Layer3, so when you put them in bridge they behalf as a switch.
The bridge port has been created. I will add inside of it the 3 ports (will show only on 1 port how to add it to the switch, you will do the same for the 2 other ports).
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Be sure that Hardware Offload is checked, because IGMP Snooping works on Hardware Offload. To know more about Hardware Offload, I invite you to check out my course Switching where I speak about Switching on MikroTik in details and about Hardware Offload; you can see on the following URL:
At the end, we will have the following ports added to the bridge:
Now, I will run the multicast traffic from the server. Remember, we didn’t enable the IGMP snooping on the switch yet, which means that both hosts will receive the multicast. Let’s check:
On the 1st PC, the multicast is working (I have already the configuring on the Router done for the multicast). Now let’s say that the 2nd PC doesn’t want the multicast traffic. In this time, he should be receiving the traffic even if he doesn’t want it. To check that, you can go to the switch and look at Ether3 interface where the 2nd PC is connected to, you will see traffic is passing. Let me show you that:
You see??? Ether3 is passing the Multicast traffic down to the host which he really doesn’t want this traffic. To be sure that this is multicast traffic, let’s go inside Ether3 interface and check that:
Indeed, it is Multicast traffic and I see it is increasing. So now the switch is sending traffic down to the 2nd PC which is wasted, and the switch is using his resources to do that. How to solve the problem? We should use IGMP snooping.
To enable IGMP snooping on the MikroTik switch, it is just 1 click. Let me show you where you can apply it:
You should go to the bridge interface and enable it globally there. That’s it.
Let’s turn on the Multicast streaming again from the server and see what the result would be.
On the 1st PC, the streaming is working perfectly.
On the 2nd PC, I didn’t open VLC player at all, so I assume that the multicast traffic will not be forwarded out of Ether3. Let’s check that from the MikroTik switch.
Indeed, Ether3 is not passing the multicast traffic down to the 2nd PC, while if you look to Ether2 you can see multicast traffic passing to the 1st PC. Wow, that’s really working now.
Now let’s say that the 2nd PC wants now to receive the streaming. I will open VLC player and see if he can see the streaming at the same time with the 1st PC.
Here is it. Both are working now.
Let’s see the traffic on the switch to see if Ether2 and Ether3 are passing the multicast traffic now:
Here we go. Both Ether2 and Ether3 are passing the traffic and everyone is happy ????
You can also do write some commands on the switch to see what is happening and monitor if IGMP snooping is working; let me show you that:
(I have stopped the streaming on the 2nd PC and left it only on the 1st PC)
Using command “interface bridge mdb print” you can see the group of multicast and to which port it is flowing. We see it is going from Ether2 because that’s where the 1st PC is connected to. We do not see Ether3 (2nd PC) because it is not requesting for the multicast traffic.
There is one more command that you can do on the switch for monitoring:
The command is “interface bridge port monitor [f]”. This command is very useful because it shows us whether the interface of the switch is connected to a multicast- router or not. As you see in the picture, it says that Ether1 is connected to a multicast-router (which is R1) and Ether2 as well Ether3 are not connected to a multicast-router because those 2 interfaces are connected to 2 PCs.
That’s all what you need to know about IGMP Snooping, I hope you enjoyed this chapter which is the last chapter of this course and I hope that I could explain everything you need to know about Multicast in MikroTik.
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