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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 24 Configuring IP Multicast Routing
Configuring Advanced PIM Features
Beginning in privileged EXEC mode, follow these steps to configure a traffic rate threshold that must
be reached before multicast routing is switched from the source tree to the shortest-path tree:
To return to the default threshold, use the no ip pim spt-threshold interface configuration command.
Modifying the PIM Router-Query Message Interval
PIM routers and multilayer switches send PIM router-query messages to determine which device will be
the DR for each LAN segment (subnet). The DR is responsible for sending IGMP host-query messages
to all hosts on the directly connected LAN.
With PIM DM operation, the DR has meaning only if IGMPv1 is in use. IGMPv1 does not have an IGMP
querier election process, so the elected DR functions as the IGMP querier. With PIM SM operation, the
DR is the device that is directly connected to the multicast source. It sends PIM register messages to
notify the RP that multicast traffic from a source needs to be forwarded down the shared tree. In this
case, the DR is the device with the highest IP address.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
access-list access-list-number {deny |
permit} source [source-wildcard]
Create a standard access list.
• For access-list-number, the range is 1 to 99.
• The deny keyword denies access if the conditions are matched.
The permit keyword permits access if the conditions are
matched.
• For source, specify the multicast group to which the threshold
will apply.
• (Optional) For source-wildcard, enter the wildcard bits in dotted
decimal notation to be applied to the source. Place ones in the
bit positions that you want to ignore.
Recall that the access list is always terminated by an implicit deny
statement for everything.
Step 3
interface interface-id Enter interface configuration mode, and specify the interface on the
leaf router that connects to the source tree.
Step 4
ip pim spt-threshold {kbps | infinity}
[group-list access-list-number]
Specify the threshold that must be reached before moving to
shortest-path tree (spt).
• For kbps, specify the traffic rate in kilobits per second. The
default is 0 kbps. The range is 0 to 4294967.
• Specify infinity if you want all sources for the specified group
to use the shared tree, never switching to the source tree.
• (Optional) For group-list access-list-number, specify the access
list created in Step 2. If the value is 0 or if the group-list is not
used, the threshold applies to all groups.
Step 5
end Return to privileged EXEC mode.
Step 6
show running-config Verify your entries.
Step 7
copy running-config startup-config (Optional) Save your entries in the configuration file.