From: Philip Downey <pdow...@brocade.com> Date: Thu, 27 Aug 2015 16:46:26 +0100
> The range of addresses between 224.0.0.0 and 224.0.0.255 inclusive, is > reserved for the use of routing protocols and other low-level topology > discovery or maintenance protocols, such as gateway discovery and > group membership reporting. Multicast routers should not forward any > multicast datagram with destination addresses in this range, > regardless of its TTL. > > Currently, IGMP reports are generated for this reserved range of > addresses even though a router will ignore this information since it > has no purpose. However, the presence of reserved group addresses in > an IGMP membership report uses up network bandwidth and can also > obscure addresses of interest when inspecting membership reports using > packet inspection or debug messages. > > Although the RFCs for the various version of IGMP (e.g.RFC 3376 for > v3) do not specify that the reserved addresses be excluded from > membership reports, it should do no harm in doing so. In particular > there should be no adverse effect in any IGMP snooping functionality > since 224.0.0.x is specifically excluded as per RFC 4541 (IGMP and MLD > Snooping Switches Considerations) section 2.1.2. Data Forwarding > Rules: > > 2) Packets with a destination IP (DIP) address in the 224.0.0.X > range which are not IGMP must be forwarded on all ports. > > IGMP reports for local multicast groups can now be optionally > inhibited by means of a system control variable (by setting the value > to zero) e.g.: > echo 0 > /proc/sys/net/ipv4/igmp_link_local_mcast_reports > > To retain backwards compatibility the previous behaviour is retained > by default on system boot or reverted by setting the value back to > non-zero e.g.: > echo 1 > /proc/sys/net/ipv4/igmp_link_local_mcast_reports > > Signed-off-by: Philip Downey <pdow...@brocade.com> Applied to net-next, thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
