You can configure the PIM interface as active or passive. The default is active. With an active interface, you can configure transmit and receive PIM control traffic. A passive interface drops all PIM control traffic, thereby reducing the load on the system. This feature is useful when you use a high number of PIM interfaces and these interfaces connect to end users, not to other switches.
A PIM passive interface does not transmit and drops messages of the following type:
hello
join
prune
register
register-stop
assert
candidate-RP-advertisement
bootstrap
If a PIM passive interface receives these types of messages, it drops them and the switch logs a message, detailing the type of protocol message and the IP address of the sending device. These log messages help to identify the device that performs routing on the interface, which is useful if you must disable a device that does not operate correctly.
Important
A device can send register and register-stop messages to a PIM passive interface, but these messages cannot be sent out of that interface.
The PIM passive interface maintains information about hosts, through IGMP, that are related to senders and receivers, but the interface does not maintain information about PIM neighbors. You can configure a BSR or an RP on a PIM passive interface.
You can also use the PIM passive interface feature as a security measure to prevent routing devices from becoming attached and participating in the multicast routing of the network.
Important
Before you change the state (active or passive) of a PIM interface, disable PIM on that interface. This action prevents instability in the PIM operations, especially when neighbors exists or the interface receives streams. After you disable PIM, the switch loses traffic for approximately 80 seconds.