46-28
Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-08
Chapter 46 Configuring IP Multicast Routing
Configuring IP Multicast Routing
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
gr
oups 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.
Beginning in privileged EXEC mode, follow these steps to filter incoming RP announcement messages.
Th
is procedure is optional.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
ip pim rp-announce-filter rp-list
access-list-number group-list
access-list-number
Filter incoming RP announcement messages.
Enter this command on each mapping agent in the network. Without
t
his command, all incoming RP-announce messages are accepted by
default.
For rp
-list access-list-number, configure an access list of candidate RP
addresses that, if permitted, is accepted for the group ranges supplied
in the group-list access-list-number variable. If this variable is
omitted, the filter applies to all multicast groups.
If more than one mapping agent is used, the filters must be consistent
ac
ross all mapping agents to ensure that no conflicts occur in the
Group-to-RP mapping information.
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