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200 Series Does not forward 224.0.0.x Multicast when IGMP is Enabled

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Information

 
Title200 Series Does not forward 224.0.0.x Multicast when IGMP is Enabled
Symptoms
  • Enabling IGMP blocks multicast frames in the 224.0.0.x range.
  • Packets specifically destined to 224.0.0.251 were tested
Environment
  • 200 Series
  • Firmware 1.02.03.0005 and below
  • Multicast
  • mDNS
  • IGMP
Cause
Firmware was not checking to see if the packet was for a well known group in compliance with RFC 4541
Resolution
Fixed in Firmware 1.02.04.0007 or Higher
Additional notes

RFC 4541     IGMP and MLD Snooping Switches Considerations      May 2006


2.1.2.  Data Forwarding Rules

   1) Packets with a destination IP address outside 224.0.0.X which are
      not IGMP should be forwarded according to group-based port
      membership tables and must also be forwarded on router ports.

      This is the main IGMP snooping functionality for the data path.
      One approach that an implementation could take would be to
      maintain separate membership and multicast router tables in
      software and then "merge" these tables into a forwarding cache.

   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.

      This recommendation is based on the fact that many host systems do
      not send Join IP multicast addresses in this range before sending
      or listening to IP multicast packets.  Furthermore, since the
      224.0.0.X address range is defined as link-local (not to be
      routed), it seems unnecessary to keep the state for each address
      in this range.  Additionally, some routers operate in the
      224.0.0.X address range without issuing IGMP Joins, and these
      applications would break if the switch were to prune them due to
      not having seen a Join Group message from the router.
 

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