There are some additional settings that you can use with IGMP-Proxy. Let me show you some:

On the upstream interface, you can use the Alternative Subnets. What does this do exactly. Well, let’s imagine that the VLC server is not directly connected to this interface and it is on another subnet, then what you can do is to set there the IP address of that server.

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Also, you can see Threshold on the interface level as you can see in the picture below:

Threshold means how much is the Time To Live (TTL) for the Multicast stream to be received to the multicast receivers. In case you are using only 1 router, then Threshold of 1 is enough, but once you have more than 1 router then you need to increase to the number of hops otherwise the multicast traffic will be dropped. So the threshold means that maximum TTL that the multicast can go.

Other settings that you can use are the following:

Query interval: This time to let the router knows how often he should send out the IGMP query messages over the downstream interfaces (I am sure by now you know what is the IGMP query messages, if not please check again chapter 3).

Query Response Interval: After the query message has been sent, the query response interval is the time that the router should wait for responses to his query messages otherwise he will know that the end device is not interested in the multicast streaming anymore.

Quick Leave: this is a check box that you can use it. In case the quick leave is checked, then an IGMP leave message is sent to the upstream interface as soon as a leave is received from the first client on the downstream interface. In another meaning, if you have 10 hosts receiving the multicast traffic and all are connected to Ether2 or the router, in case one host doesn’t need the multicast stream and the quick leave is checked on the router, then this host will inform the downstream interface (Ether2) which in turn will inform the upstream interface and, guess what, the upstream interface will not send the multicast stream down to Ether2 anymore which lead that all 9 other hosts will not be able to receive the multicast stream anymore. That’s why MikroTik recommends that you don’t check Quick Leave unless you have only 1 user as a multicast receiver.

To finish with this chapter, you may have seen the Tab MFC on the IGMP-Proxy. MFC means Multicast Forwarding Cache.

What is exactly MFC? You have to think it is like a routing table when speaking about Unicast. So, It is a table where it create dynamically entries showing the multicast group (in our case 239.1.2.3), the source of the multicast stream which is 192.168.1.2, then upstream interface which is Ether1 and the downstream interface which is Ether2 and some packets’ statistics.

This is created dynamically, but you can create is statically. In case you create an entry statically, then the same dynamic one will be removed and the static one will be the one used. For example, if we want to create the entry of our LAB statically, we should do the following:

Once you click on OK, the static entry will be added as you see below in the picture:

We still see the dynamic entry which is the same, but the static one will be the one used once we run the multicast streaming and the dynamic one will disappear. To be sure of this, I will run again the multicast and see which of the 2 entries will show the packets.

As you can see, the static one is the one used and the dynamic one has disappeared.

That’s all what you need to know about IGMP-Proxy in MikroTik, I hope you enjoyed the chapter and see you in the upcoming one.
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