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Catalyst 3750 SwitchSoftware Configuration Guide
OL-8550-09
Chapter46 Configuring IP Multicast Routing
Configuring IP Multicast Routing
Configuring PIM Stub Routing
The PIM Stub routing feature supports multicast routing between the distribution layer and the access
layer. It supports two types of PIM interfaces, uplink PIM interfaces, and PIM passive interfaces. A
routed interface configured with the PIM passive mode does not pass or forward PIM control traffic, it
only passes and forwards IGMP traffic.

PIM Stub Routing Configuration Guidelines

Follow these guidelines when enabling PIM stub routing on an interface:
•Before configuring PIM stub routing, you must have IP multicast routing configured on both the stub
router and the central router. You must also have PIM mode (dense-mode, sparse-mode, or
dense-sparse-mode) configured on the uplink interface of the stub router.
•The PIM stub router does not route the transit traffic between the distribution routers. Unicast
(EIGRP) stub routing enforces this behavior. You must configure unicast stub routing to assist the
PIM stub router behavior. For more information, see the “Configuring EIGRP Stub Routing” section
on page 38-42.
•Only directly connected multicast (IGMP) receivers and sources are allowed in the Layer 2 access
domains. The PIM protocol is not supported in access domains.
•The redundant PIM stub router topology is not supported.

Enabling PIM Stub Routing

Beginning in privileged EXEC mode, follow these steps to enable PIM stub routing on an interface. This
procedure is optional.
To disable PIM stub routing on an interface, use the no ip pim passive interface configuration command.
In this example, IP multicast routing is enabled, Switch A PIM uplink port 25 is configured as a routed
uplink port with spare-dense-mode enabled. PIM stub routing is enabled on the VLAN 100 interfaces
and on Gigabit Ethernet port 20 in Figure 46-2:
Switch(config)# ip multicast-routing distributed
Switch(config)# interface GigabitEthernet3/0/25
Switch(config-if)# no switchport
Switch(config-if)# ip address 3.1.1.2 255.255.255.0
Switch(config-if)# ip pim sparse-dense-mode
Switch(config-if)# exit
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 interface interface-id Specify the interface on which you want to enable PIM stub routing, and
enter interface configuration mode.
Step3 ip pim passive Configure the PIM stub feature on the interface.
Step4 end Return to privileged EXEC mode.
Step5 show ip pim interface Display the PIM stub that is enabled on each interface.
Step6 show running-config Verify your entries.
Step7 copy running-config startup-config (Optional) Save your entries in the configuration file.