# Configuring Point-to-Multipoint LSPs

To set up a point-to-multipoint LSP, you configure the primary LSP from the ingress router and the branch LSPs that carry traffic to the egress routers. The configuration of the primary point-to-multipoint LSP is similar to a signaled LSP. In addition to the conventional LSP configuration, you specify a path name on the primary LSP and this same path name on each branch LSP. By default, the branch LSPs are dynamically signaled by means of CSPF and require no configuration. You can alternatively configure the branch LSPs as a static path.

Because E Series routers can only function as egress routers, you must use M-series routers running Junos OS as ingress routers to enable point-to-multipoint LSPs to send packets through the network to the endpoints connected to the egress routers.

Observe the following guidelines to deliver multicast data using point-to-multipoint LSPs on the egress E Series routers:

- The IP interface on which the packet arrives must be an IGMP-owned interface. An IGMP-owned interface refers to an interface in which IGMP is the only multicast protocol enabled.
- The actual route to the source must be through an IGMP-owned interface.

The configuration of an E Series router as an egress router depends on the type of label advertised for the LSR that is the egress router for the prefix. Penultimate hop popping (PHP) is the default when RSVP-TE or LDP is the signaling protocol.

If the egress router advertises an implicit null label to achieve PHP on an upstream neighbor, enable IP IGMP on the static physical interface on which the unlabeled multicast packet is received by the router by using the ip igmp interface configuration command.

    host1(config-if)#ip igmp

If the egress router advertises an explicit null or non-null label to its upstream neighbour to include a label in all MPLS packets, complete the following steps to configure an E Series router as an egress router:

1. Create a profile by using the profile command. Add commands to enable IP IGMP and IP processing on the loopback interface in the profile.

       host1(config)#profile mplsdynip
       host1(config-profile)#ip igmp
       host1(config-profile)#ip unnumbered loopback 0

2. Create a dynamic IPv4 interface on top of MPLS major interfaces and specify the profile that you created in the previous step to set attributes for this interface.

       host1(config)#mpls create-dynamic-interfaces ip on-major-interfaces profile dynip

For all types of labels that are advertised for the LSR that is the egress router for the prefix, you must complete the following steps, in addition to those detailed earlier, on the E Series router:

1. Enable IGMP on the interface which owns the route to the source by using the ip igmp command. Because the route to the source can change dynamically, we recommend that you enable IGMP on all interfaces of the router or, at least, on all interfaces that might be the next hop interface to the source.
2. Disable the multicast reverse path forwarding (RPF) check policy for all the streams that will be delivered on the point-to-multipoint LSP by using the ip multicast-routing disable-rpf-check command. For more information, see Enabling and Disabling RPF Checks in the JunosE Multicast Routing Configuration Guide.

#### Related Documentation

- Point-to-Multipoint LSPs Overview
- show mpls tunnels