Administrator Guide

IPv4 Multicast Policies
The following sections describe IPv4 multicast policies.
• Limiting the Number of Multicast Routes
• Preventing a Host from Joining a Group
• Rate Limiting IGMP Join Requests
• Preventing a PIM Router from Forming an Adjacency
• Preventing a Source from Registering with the RP
• Preventing a PIM Router from Processing a Join
Limiting the Number of Multicast Routes
When the total number of multicast routes on a system limit is reached, the Dell Networking OS does not
process any IGMP or multicast listener discovery protocol (MLD) joins to PIM — though it still processes leave
messages — until the number of entries decreases below 95% of the limit.
When the limit falls below 95% after hitting the maximum, the system begins relearning route entries through
IGMP, MLD, and MSDP.
• If the limit is increased after it is reached, join subsequent join requests are accepted. In this case,
increase the limit by at least 10% for IGMP and MLD to resume.
• If the limit is decreased after it is reached, the system does not clear the existing sessions. Entries are
cleared after a timeout (you may also clear entries using clear ip mroute).
NOTE
: The Dell Networking OS waits at least 30 seconds between stopping and starting IGMP join
processing. You may experience this delay when manipulating the limit after it is reached.
When the multicast route limit is reached, the system displays the following:
3w1d13h: %RPM0-P:RP2 %PIM-3-PIM_TIB_LIMIT: PIM TIB limit reached. No new
routes will
be learnt until TIB level falls below low watermark.
3w1d13h: %RPM0-P:RP2 %PIM-3-PIM_TIB_LIMIT: PIM TIB below low watermark.
Route learning
will begin.
To limit the number of multicast routes, use the following command.
• Limit the total number of multicast routes on the system.
CONFIGURATION mode
ip multicast-limit
The range if from 1 to 50000.
The default is 15000.
Multicast Features 622