Dell S4820T, Configuration Manual

Page: 664 / 1178

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 16000.
The default is 4000 .
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 this hardware
space limitation. The opposite is also true, the CAM partition might not be exhausted at the time the
system-wide route limit is reached using the
ip multicast-limit
command.
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
the 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
Dell Networking OS Behavior : Do not enter the
ip igmp access-group
command before creating the
access-list. If you do, after entering your first deny rule, Dell Networking OS clears the 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 Dell Networking OS from clearing the routing table by entering a permit any rule
with a 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.
664
Multicast Features