# PIM - Multicast Groups

When you run PIM-SM, there are certain options that you can set at the virtual router (VR) level to control traffic to and from the VR. Settings defined at the VR level affect all PIM-SM-enabled interfaces in the VR.

## Restricting Multicast Sources

You can control the sources from which a multicast group receives data. You identify the allowed source(s) in an access list, then link the access list to multicast groups. This prevents unauthorized sources from sending data into your network. When you use this feature, the NetScreen device drops multicast data from sources not in the list.

### To Restrict Multicast Sources

1. Enter the necessary information:

Mgroup: Enter the IP address of the multicast group to which you are linking the access list.

Accept Source: Select the ID of the access list for the allowed sources.

2. Click Add to save the configuration.

## Restricting Rendezvous Points

You can control which Rendezvous Points (RPs) are mapped to a multicast group. You identify the allowed RP(s) in an access list, then link the access list to the multicast groups. When the VR receives a bootstrap message for a particular group, it checks its list of allowed RPs for that group. If it does not find a match, then it does not select an RP for the multicast group.

### To Restrict RPs

1. Enter the necessary information:

Mgroup: Enter the IP address of the multicast group to which you are linking the access list.

Accept RP: Select the ID of the access list for the allowed RPs.

2. Click Add to save the configuration.