Hi all, (CRS326 routerOS 7.14.1)
I have a bridge with igmp snooping enabled, several rj45 delivering multicast streams and one port linked into another network where the igmp querier is configured.
It all works as it should, igmp querier is detected by the bridge and displayed in the bridge status section.
Where can I see the currently active multicast groups? In the past with slightly different configs, either current device as igmp querier or with PIM, I could see the active multicast either in the MDB section in bridge (winbox) or in PIM in one of the last tabs.
Are they invisible to "print" because hardware offload is active and the filtering happens in the switch chip?
I know torch is a way to, but that will disable hardware offload while torch is running, right? And if I want to include mcast addresses utilisation in snmp or api, the torch is not the way.

Thanks!

one port linked into another network where the igmp querier is configured.

By "another network" do you mean another subnet, putting it beyond a routing layer, inside another broadcast domain, or do you mean another segment of the same LAN?

There needs to be one querier per subnet; no more, no less.

igmp querier is detected by the bridge

I think you're confusing cause for effect. In RouterOS, the bridge doesn't "detect" the querier, the bridge offers the option of being the LAN's multicast querier. If you have that box checked…


…it begins sending out periodic "are you still interested in this stream" messages to all ports that claimed to want that stream. If the switch doesn't get an answer within its timeout, it pinches the stream off by removing it from its MDB, saving bandwidth.

This is why you need one querier per subnet and one only. Two backseat drivers are worse than one, and we have no choice but to tolerate the one.

(In an ideal world, every client would announce when it is going off-LAN and close down its multicast streams first, obviating the need for a multicast querier.)

Where can I see the currently active multicast groups? …Are they invisible to "print"

The MDB contents are fully visible to "print" here on my CRS328-24G:

Thanks for the reply. I'll clarify.
The "other network" is the same vlan(flat) same subnet, just another brand of switches where the querier is configured, with that querier IP in the same subnet.
Our mikrotik is not the querier and should not be the querier for the same reasons you explained.
My logic is: if instead of this mikrotik I would use a HP procurve or aruba switch (or others, netgear, zyxel etc), with IGMP snooping being enabled and querier disabled on this switch, (as we said, we don't want a 2nd querier, we already have one), running a command like
"show ip igmp" will display the current active querier (IP and physical port where it's connected)
[note our mikrotik does that in the bridge status, it detects the external querier, IP and port, so that part is ok]
back on the HP/aruba/etc we also see all active multicast groups/groups that are in use/requested by a client.
On our mikrotik we cannot see the active groups.

My suspicion is that the IGMP snooping happens with hardware offload and the OS isn't pulling all the info from the switch chip.
Maybe MIKROTIK OFFICIAL or something can confirm

Edit: in your screenshot we can see the multicasts because your mikrotik IS the querier, mine isnt'. If you have an edge mikrotik connected to your first, which will of course NOT have the "multicast querier" checkbox enabled, it will only have igmp snooping enabled, you won't see the active multicasts anymore, that's my issue/question.
Thanks!

My suspicion is that the IGMP snooping happens with hardware offload and the OS isn't pulling all the info from the switch chip.

While it is true that IGMP snooping is a layer 2 function best offloaded to the switch chip, that doesn't mean you can only see the MDB on devices configured as the querier, or as pure L2 switches. I just checked my bedroom switch, very much an edge distribution device, and it's currently showing 24 entries in its MDB, while the Internet gateway router is showing 52. The core switch on which the screenshot above was taken is sitting between them, acting as the LAN's sole IGMP querier.

Maybe it's time you showed your configuration?

Do you see the IGMP packets come through at all?

Maybe MIKROTIK OFFICIAL or something can confirm

You might be that lucky; it does occasionally occur.

If you're determined to speak to MT officials and not end-users like me, though, your best path is to send a message to support. This is primarily a user-to-user forum.