Administrator Guide
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 congure 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 specied 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
lter 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 lter, 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