Reference Guide

636 | Multicast Features
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Limit the Number of Multicast Routes
When the limit is reached, FTOS does not process any IGMP or 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, you
must increase the limit by at least 10% for IGMP and MLD to resume.
• If the limit is decreased after it is reached, FTOS does not clear the existing sessions. Entries are
cleared upon a timeout (you may also clear entries using
clear ip mroute).
When the multicast route limit is reached, FTOS displays Message 1.
Prevent a Host from Joining a Group
You can prevent a host from joining a particular group by blocking specific IGMP reports. Create an
extended access list containing the permissible source-group pairs. Use the command
ip igmp
access-group access-list-name from INTERFACE mode to apply the access list.
Task Command Syntax Command Mode
Limit the total number of multicast routes on the system.
ip multicast-limit
Range: 1-50000
Default: 15000
CONFIGURATION
Note: FTOS 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.
Message 1 Multicast Route Limit Error
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.
Note: The IN-L3-McastFib CAM partition is used to store multicast routes and is a separate hardware limit
that is exists per port-pipe. Any software-configured limit might be superseded by this hardware space
limitation. The opposite is also true, the CAM partition might not be exhausted at the time the system-wide
route limit set by the ip multicast-limit is reached.
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 Figure 33-2), since IGMPv2 hosts do not know
in advance who the source is for the group in which they are interested.