# Using PIM Sparse Mode Join Filters

You can use PIM sparse mode join filters to prevent multicast state from being created in the PIM sparse mode router. The filters are applied to join entries in PIM join/prune messages that are received from PIM sparse mode neighbors.

By denying joins at the edge of a network, you can limit the multicast state and traffic in the network. By accepting only certain joins, you can control which multicast services an end user can receive. PIM join filters also reduce the potential for denial of service (DoS) attacks where large numbers of joins forwarded to each router on the RPT can result in a PIM state explosion and very high memory consumption.

For information about how to create access lists, see Configuring Routing Policy in the JunosE IP Services Configuration Guide.

ip pim join-filter

- Use to specify an extended access list that you want this PIM interface to use as a join filter.
- You can apply the join filter at the global level or at the interface level.
- If an interface-level filter exists, it takes precedence over the global-level filter.
- Example 1
  host1(config)#ip pim join-filter gold
- Example 2
  host1(config-interface)#ip pim join-filter gold
- Use the no version to remove the filter association.
- See ip pim join-filter.