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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
Chapter 1 Configuring IP Multicast Routing
Configuring IP Multicast Routing
To remove the PIM device configured as the candidate RP, use the no ip pim send-rp-announce
interface-id global configuration command. To remove the switch as the RP-mapping agent, use the no
ip pim send-rp-discovery global configuration command.
This example shows how to send RP announcements out all PIM-enabled interfaces for a maximum of 31
hops. The IP address of port 1 is the RP. Access list 5 describes the group for which this switch serves
as RP:
Switch(config)# ip pim send-rp-announce gigabitethernet1/0/1 scope 31 group-list 5
Switch(config)# access-list 5 permit 224.0.0.0 15.255.255.255
Preventing Join Messages to False RPs
Find whether the ip pim accept-rp command was previously configured throughout the network by
using the show running-config privileged EXEC command. If the ip pim accept-rp command is not
configured on any device, this problem can be addressed later. In those routers or multilayer switches
already configured with the ip pim accept-rp command, you must enter the command again to accept
the newly advertised RP.
To accept all RPs advertised with Auto-RP and reject all other RPs by default, use the ip pim accept-rp
auto-rp global configuration command. This procedure is optional.
If all interfaces are in sparse mode, use a default-configured RP to support the two well-known
groups 224.0.1.39 and 224.0.1.40. Auto-RP uses these two well-known groups to collect and distribute
RP-mapping information. When this is the case and the ip pim accept-rp auto-rp command is
configured, another ip pim accept-rp command accepting the RP must be configured as follows:
Switch(config)# ip pim accept-rp 172.10.20.1 1
Switch(config)# access-list 1 permit 224.0.1.39
Switch(config)# access-list 1 permit 224.0.1.40
Filtering Incoming RP Announcement Messages
You can add configuration commands to the mapping agents to prevent a maliciously configured router
from masquerading as a candidate RP and causing problems.
Step 5
ip pim send-rp-discovery scope ttl Find a switch whose connectivity is not likely to be interrupted, and
assign it the role of RP-mapping agent.
For scope ttl, specify the time-to-live value in hops to limit the RP
discovery packets. All devices within the hop count from the source
device receive the Auto-RP discovery messages. These messages tell
other devices which group-to-RP mapping to use to avoid conflicts (such
as overlapping group-to-RP ranges). There is no default setting. The
range is 1 to 255.
Step 6
end Return to privileged EXEC mode.
Step 7
show running-config
show ip pim rp mapping
show ip pim rp
Verify your entries.
Display active RPs that are cached with associated multicast routing
entries.
Display the information cached in the routing table.
Step 8
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
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