Howdy, Question for those more versed in IPv6 than I: Is there any harm from dropping ICMPv6 multicast listener discovery reports in a network which does NOT use any multicast routing (i.e. only uses multicast which stays within the local link). I see a LOT of idle node chatter in the form of these reports which, of course, flood every station since they are themselves multicast. As far as I can tell they are used only to tell a multicast router whether to repeat a particular set of multicast packets to the instant link. Which in my network is -never- because there are no routed multicast packets to be repeated. Regards, Bill Herrin -- William Herrin bill@herrin.us https://bill.herrin.us/
If you enable MLD snooping on your switches, the switch will block multicast going out irrelevant ports. The idea is to reduce broadcast in a broadcast domain. On Fri, Jun 4, 2021 at 11:03 PM William Herrin <bill@herrin.us> wrote:
Howdy,
Question for those more versed in IPv6 than I: Is there any harm from dropping ICMPv6 multicast listener discovery reports in a network which does NOT use any multicast routing (i.e. only uses multicast which stays within the local link). I see a LOT of idle node chatter in the form of these reports which, of course, flood every station since they are themselves multicast. As far as I can tell they are used only to tell a multicast router whether to repeat a particular set of multicast packets to the instant link. Which in my network is -never- because there are no routed multicast packets to be repeated.
Regards, Bill Herrin
-- William Herrin bill@herrin.us https://bill.herrin.us/
Are your links or hosts limited in some way or broadcast domains of some unreasonable size? Most of the competent switching or managed wireless products will snoop or otherwise handle this overhead in a sane manner. Otherwise this at best would seem to be an over-optimization.
From my days on a giant campus network the current pps rate of MLD chatter was much lower than the IPX/SAP broadcasts we had from 20-25 yrs earlier.
Dale Thus spake William Herrin (bill@herrin.us) on Fri, Jun 04, 2021 at 02:01:19PM -0700:
Howdy,
Question for those more versed in IPv6 than I: Is there any harm from dropping ICMPv6 multicast listener discovery reports in a network which does NOT use any multicast routing (i.e. only uses multicast which stays within the local link). I see a LOT of idle node chatter in the form of these reports which, of course, flood every station since they are themselves multicast. As far as I can tell they are used only to tell a multicast router whether to repeat a particular set of multicast packets to the instant link. Which in my network is -never- because there are no routed multicast packets to be repeated.
Regards, Bill Herrin
-- William Herrin bill@herrin.us https://bill.herrin.us/
On Mon, Jun 7, 2021 at 9:34 AM Dale W. Carder <dwcarder@es.net> wrote:
Are your links or hosts limited in some way or broadcast domains of some unreasonable size? Most of the competent switching or managed wireless products will snoop or otherwise handle this overhead in a sane manner. Otherwise this at best would seem to be an over-optimization.
From my days on a giant campus network the current pps rate of MLD chatter was much lower than the IPX/SAP broadcasts we had from 20-25 yrs earlier.
Hi Dale, Actually, I'm doing station to station encryption with macsec using multiple SCIs at each station so there's a magnification effect of encrypted multicast packets that the switch can't snoop even if it wanted to -- all the intermediate equipment sees is an opaque ethernet frame with the broadcast flag set. Regards, Bill Herrin -- William Herrin bill@herrin.us https://bill.herrin.us/
participants (3)
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Baldur Norddahl -
Dale W. Carder -
William Herrin