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How to prevent "IPv4 multicast entry not added. Hardware L3 table full." log messages

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TitleHow to prevent "IPv4 multicast entry not added. Hardware L3 table full." log messages
Objective
Hardware L3 Table full messages are logged for IPv4 multicast entries, this article list possible solutions to prevent these.  If the solutions do not work you are likely hitting a hardware limitation.

The log message:
<Warn:Kern.IPv4Mc.Warning> Slot-<slot number>: IPv4 multicast entry not added.  Hardware L3 Table full.
Environment
  • Black Diamond
  • Summit
  • EXOS all versions
Procedure
In below 2 links you will be provided with many different commands used to optimize the way multicast entries are stored in the switch.  Some of these commands can effect your switch in different ways, so please read the description on each command.
Additional notes
On switches that are not configured for multicast routing, change the method of multicast traffic learning (IGMP forwarding mode) from 'source-group-vlan' (S,G,V) to  'group-vlan' (*,G,V).  Using (S,G V) the switch will allocate one space in the L3 hash table for each source of a multicast packet going to the same destination.  Changing the forwarding mode to (*,G,V), the switch summarizes table entries for multiple sources going to the same destination.  This reduces the amount of L3 hash table space used.

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