Talk:Multicast address

Ethernet Multicast is IP Multicast too?

It is not completely clear if the Ethernet multicast addresses mentioned in the article are exclusively used in combination with IP Multicast protocols rather than any alternate multicast protocols.

If this is the case I would suggest this article to link directly to the protocol it applies to, as in:

In computer networking a multicast address is an identifier for a group of hosts that have joined a multicast group using the IP Multicast protocol.

--SymlynX 17:33, 26 November 2006 (UTC)

There are other applications for Ethernet multicast besides carrying IP multicast. ~Kvng (talk) 20:13, 20 May 2021 (UTC)

IP address format

In the article, it says, "It ranges from 224.0.0.0 to 239.255.255.255, or, equivalently, 224.0.0.0/4" - shouldn't this last part read "224/4"? Hex equivalents would be E0.00.00.00 to EF.FF.FF.FF. Maybe the article should mention and define the two different styles of writing the IP ranges? Cbdorsett 07:37, 25 January 2007 (UTC)

"224/4" is read as 0.0.0.224/24 if you strictly adhere to standards. What you can write is 224.0/24, but 224.0.0.0/4 is perfectly fine and the least confusing. --Eqvinox (talk) 19:11, 28 June 2011 (UTC)

Which standards are these? When omitting zeros in an IPv4 address, they should be added at the end, not the beginning. This can also be seen in the RFCs, e.g. RFC 1918 p. 3 lists the private ranges as 10/8, 172.16/12, and 192.168/16. Tommiie (talk) 09:45, 28 June 2017 (UTC)

802.11 Ngamboithang (talk) 22:18, 29 January 2022 (UTC)

L2 before L3

I would like to suggest that the Ethernet section at the bottom is moved to before the IPv4 and IPv6 section. This makes the order of the sections consistent with the layer order. —Preceding unsigned comment added by 77.110.39.122 (talk) 07:53, 12 December 2008 (UTC)

In network stack diagrams, the lower layers are at the bottom. There may be other reasons to move Ethernet higher, but this isn't a strong one. ~Kvng (talk) 20:13, 20 May 2021 (UTC)

Ethernet-specific

A new contribution warns that IGMP snooping does not work with certain ranges of multicast addresses. The source provided look reliable but is dated 1992-2004 so may not reflect the current state of things. ~Kvng (talk) 15:26, 17 January 2023 (UTC)

Per RFC 4541, section 2.1.2 paragraph 2, any IGMP reports related to link-local multicast addresses (224.0.0.0/24) are ignored by IGMP snoopers which means that other types of packets bound to link-local multicast addresses get flooded everywhere. Perhaps that's what it's referring to. Nanotik (talk) 14:30, 18 February 2024 (UTC)

In fact, while in my experience the above holds, Wikipedia's page on IGMP snooping says that the RFC is by no means authorative as it's an informational one and it's up to everyone to decide how it goes, so Cisco's way of snooping may not be how TP-Link or Mikrotik do it. Nanotik (talk) 15:06, 18 February 2024 (UTC)

Doesn't explain how they work

This doesn't explain how multicast addresses work. Sure, there are certain ones that mean certain things, but how do you use them? What do you use them for? I want to send a packet to multiple receivers, so we pre-arrange that I will send to some multicast address, and then the receivers arrange to receive on that multicast address somehow? Is that it? How is that accomplished?

Hotpine (talk) 21:24, 29 April 2023 (UTC)

Let us know if you don't find what you're looking for in the Multicast article. I've added a hatnote link to this article to help readers find this (though arguably this is unnecessary since it is already linked in the lead). ~Kvng (talk) 13:57, 22 February 2024 (UTC)