Configuring a Multicast RPF Check Policy for Point-to-Multipoint LSPs
You can control whether a reverse path forwarding (RPF) check is performed for a source and group entry before installing a route in the multicast forwarding cache. This makes it possible to use point-to-multipoint LSPs to distribute multicast traffic to PIM islands situated downstream from the egress routers of the point-to-multipoint LSPs.
By configuring the rpf-check-policy statement, you can disable RPF checks for a source and group pair. You would typically configure this statement on the egress routers of a point-to-multipoint LSP, because the interface receiving the multicast traffic on a point-to-multipoint LSP egress router might not always be the RPF interface.
You can also configure a routing policy to act upon a source and group pair. This policy behaves like an import policy, so if no policy term matches the input data, the default policy action is “acceptance.” An accept policy action enables RPF checks. A reject policy action (applied to all source and group pairs that are not accepted) disables RPF checks for the pair.
To configure a multicast RPF check policy for a point-to-multipoint LSP, specify the RPF check policy using the rpf-check-policy statement:
You can include this statement at the following hierarchy levels:
- [edit routing-options multicast]
- [edit logical-systems logical-system-name routing-options multicast]
You also must configure a policy for the multicast RPF check. You configure policies at the [edit policy-options] hierarchy level. For more information, see the Routing Policy Configuration Guide.
 | Note: When you configure the rpf-check-policy statement, the Junos OS cannot perform RPF checks on incoming traffic and therefore cannot detect traffic arriving on the wrong interface. This might cause routing loops to form. |
Example: Configuring Multicast RPF Check Policy for a Point-to-Multipoint LSP
Configure a policy to ensure that an RPF check is not performed for sources with prefix 128.83/16 or longer that belong to groups having a prefix of 228/8 or longer:
