What's the deal with IGMP?
This is mostly a question to educate myself and hopefully maybe others. I have tried to scan all the IGMP-related threads (and read up on Wikipedia etc.), but they span a long timeframe across a number of router models and firmware versions, and have lots of information that I couldn't stitch together since I am not a "network engineer."
I have 1x RBR50v2 and 3x RBS50v2, with wired backhaul, all running the latest 184.108.40.206 firmware, behind an Xfinity 1000/40 service. There is a setting on the web management interface under ADVANCED > Setup > WAN Setup by the name "Disable IGMP Proxying" which is checked by default, i.e. IGMP Proxying is DISABLED by default. Btw, I have no idea if that setting is new to 220.127.116.11... Also, there is a dropdown next to it, presumably for when the proxying is enabled, with the values AUTO, IGMPv2 and IGMPv3. The help on that checkbox says "The IGMP Proxying function lets a LAN PC to receive the multicast traffic it is interested in from the Internet. You can click this check box to disable the function if you do not need it." which doesn't tell me much since I have no idea when one would want their local PC in their home network want to accept "multicast traffic" (what is that, even?) from the wild bad world of internet on the other side of my router.
I also have slightly more advanced switches than your run of the mill consumer grade ones, primarily with SNMP enabled, among other things, like seven of GS108Tv3 + one GS716Tv3 + one GS724Tv4, to distribute gigabit wired network in the walls of my house to all the rooms etc. They all have some form of IGMP management on their management webpage. For example, on GS108Tv3, running latest firmware 18.104.22.168, it takes the form SWITCHING > Multicast > IGMP Snooping. On that page, one can Enable/Disable two settings, "IGMP Snooping Status" and "Validate IGMP IP header", and if enabled, one can further muck around with port-level IGMP-related functionality which I won't get into. Those two settings are by default ENABLED. And, as luck would have it, if you set both to DISABLED, and if GS108Tv3 goes through a power outage, it comes back as IGMP Snooping Status re-set to ENABLED. Yuck. I reported that by opening a support ticket (case #41462667, if any Netgear person is reading this and wants to do something about it).
Bunch of stuff I read on misc community threads, it seemed like Orbi was NOT implementing any IGMP stuff, that was causing some issues with things like IP security cameras, causing things to hog traffic and slow down everything else on the home network. Yet, I now see the above setting on Orbi. And, @FURRYe38 had been recommending in his posts to disable IGMP on any smart/managed switches, which I have been by setting both of those IGMP settings on my switches to DISABLE.
The problem is, I have no real understanding as to why I am doing this, except for following sage advice.
So, what really is IGMP doing in practical terms, as in:
- what kind of equipment set up in my house would benefit from enabling it both on the router and switches,
- what would be the problems with enabling (if any) given all that bad juju posts I read about Orbi and IGMP, and
- what would be the problems with leaving them enabled even if I don't have such a set up, and
- what would be problematic and/or impossible if I have such hardware set up on my network but leave IGMP disabled in Orbi and switches, or
- leave everything at their default values regardless if I have any hardware set up that could benefit from proper IGMP functionality?
In general, I would love to leave all those settings at their factory default values (DISABLED on Orbi and ENABLED on the switches), and expect everything to work as I go out and shop for IoT stuff and add them to the landscape of my home network. No so?
Any DEFINITIVE educational guidance would be much appreciated.