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Rate Limiting IGMP Join Requests
If you expect a burst of IGMP Joins, protect the IGMP process from overload by limiting that rate at which
new groups can be joined.
Hosts whose IGMP requests are denied will use the retry mechanism built-in to IGMP so that they’re
membership is delayed rather than permanently denied.
• Limit the rate at which new groups can be joined.
INTERFACE mode
ip igmp group-join-limit
To view the enable status of this feature, use the show ip igmp interface command from EXEC
Privilege mode.
Preventing a PIM Router from Forming an Adjacency
To prevent a router from participating in PIM (for example, to configure stub multicast routing), use the
following command.
• Prevent a router from participating in protocol independent multicast (PIM).
INTERFACE mode
ip pim neighbor-filter
Preventing a Source from Registering with the RP
To prevent the PIM source DR from sending register packets to RP for the specified multicast source and
group, use the following command. If the source DR never sends register packets to the RP, no hosts can
ever discover the source and create a shortest path tree (SPT) to it.
• Prevent a source from transmitting to a particular group.
CONFIGURATION mode
ip pim register-filter
In the following example, Source 1 and Source 2 are both transmitting packets for groups 239.0.0.1 and
239.0.0.2. R3 has a PIM register filter that only permits packets destined for group 239.0.0.2. An entry is
created for group 239.0.0.1 in the routing table, but no outgoing interfaces are listed. R2 has no filter, so
it is allowed to forward both groups. As a result, Receiver 1 receives only one transmission, while Receiver
2 receives duplicate transmissions.
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Multicast Features