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● Limit the total number of multicast routes on the system.
CONFIGURATION mode
ip multicast-limit
The range is from 1 to 16000.
The default is 4000.
NOTE: The IN-L3-McastFib CAM partition stores multicast routes and is a separate hardware limit that exists per port-pipe.
Any software-configured limit may supersede this hardware space limitation. The opposite is also true, the CAM partition
might not be exhausted at the time the system-wide route limit is reached using the ip multicast-limit command.
Preventing a Host from Joining a Group
You can prevent a host from joining a particular group by blocking specific IGMP reports using an extended access list
containing the permissible source-group pairs.
NOTE: For rules in IGMP access lists, source is the multicast source, not the source of the IGMP packet. For IGMPv2, use
the keyword any for source (as shown in the following example) because the IGMPv2 hosts do not know in advance who
the source is for the group in which they are interested.
To apply the access list, use the following command.
● Apply the access list.
INTERFACE mode
ip igmp access-group access-list-name
Dell EMC Networking OS Behavior: Do not enter the ip igmp access-group command before creating the access-list.
If you do, after entering your first deny rule, the Dell EMC Networking OS clears the multicast routing table and re-learns
all groups, even those not covered by the rules in the access-list, because there is an implicit deny all rule at the end of all
access-lists. Therefore, configuring an IGMP join request filter in this order might result in data loss. If you must enter the
ip igmp access-group command before creating the access-list, prevent the Dell EMC Networking OS from clearing the
routing table by entering a permit any rule with a high sequence number before you enter any other rules.
In the following example, virtual local area network (VLAN) 400 is configured with an access list to permit only IGMP reports
for group 239.0.0.1. Though Receiver 2 sends a membership report for groups 239.0.0.1 and 239.0.0.2, a multicast routing table
entry is created only for group 239.0.0.1. VLAN 300 has no access list limiting Receiver 1, so both IGMP reports are accepted
and two corresponding entries are created in the routing table.
Multicast Features
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