On Jun 06, 2023, Jim Jackson wrote:
> On Tue, 6 Jun 2023, Dan Purgert wrote:
> > (references / new reading material would be appreciated ^_^ )
>
> As far as I remember, IPv6 was designed to be more efficient on LANs. It
> was designed when many LANs were still esentially collision domains!!!
> For most of us "collision domains" are a thing of the past, though I
> still have a couple of bits of gear that use thin ethernet and a thin
> ethernet to Twisted pair repeater. But they haven't been powered up
> recently

Yeah, I "sort of" remember efficiency being a thing, but always took it
on the numbering side ("you get a /64!").
> [...]
> https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6_basic/configuration/xe-3se/3850/ip6-neighb-disc-xe.html
>
> The closest you get to a broadcast is sending data to the All Nodes
> multicast group.
>
> So the question is - how good are cheap switches at implementing
> multicast at link level efficiently. So you need switches that support
> MLD snooping - MLD being the IPv6 version of IPv4's IGMP. I
> understand that there is an equivalence between IGMP and MLD.

Given their capabilities with other things, "poor" :D
>
> It probably eventually means instead of number of MAC addresses a switch
> can store for switching purposes, there may be some limit on space to
> store where all the members of the multicast addresses are, on a large
> network.

My moderately expensive ones ($400 range, IIRC) here allegedly have the
capacity for 16k (2^14) MAC addresses...

Couple of random "small office" ones I looked up quick-like (Netgear /
trendNET) in the <$400 range are apparently 4k.


> I came across this ...
>
> https://gist.github.com/njh/5c74614a92eb6c088ae9334db70df76a
>
> but didn't see a date. It appears a lot of managed switches support
> snooping but not sure about unmanaged cheap switches.

Most recent revision is 2018, so not too old (but already 5y, so they're
probably all discontinued now anyway).
>
> This discusses some of the issues ...
>
> https://blogs.infoblox.com/ipv6-coe/how-many-ipv6-nodes-can-you-have-on-a-lan/


Thanks for the links / info!

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