Reference Guide

When the multicast route limit is reached, FTOS 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.
NOTE: The IN-L3-McastFib CAM partition is used to store multicast routes and is a separate hardware limit that
exists per port-pipe. Any software-configured limit may supersede 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 the ip
multicast-limit command sets is reached.
Preventing 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.
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 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
FTOS Behavior: Do not enter the ip igmp access-group command before creating the access-list. If you do, after
entering your first deny rule, FTOS clears 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 FTOS from clearing the routing table by entering a permit any rule
with 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.
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