Each virtual router responds to mrinfo requests with a list of multicast interfaces and
their IP addresses. If appropriate, the virtual router also supplies the following information
for each interface:
•
Current functional status of the interface (for example, if the interface is down).
•
Information as to whether the interface is disabled and the reason for the interface
being disabled—either because IP is not configured on the interface or because the
interface has been disabled through the software.
•
Whether the interface is performing the IGMP queries for this subnet.
•
Information about PIM neighbors:
If PIM is configured on the interface, the virtual router supplies a list of the interface's
PIM neighbors and indicates which neighbors are leaf neighbors.
•
Information about DVMRP and GRE tunnels:
If the interface is an endpoint of a tunnel, the virtual router specifies the IP address of
the endpoint of the tunnel.
BGP Multicasting
BGP multicasting (MBGP) is an extension of the BGP unicast routing protocol. Many of
the functions available for BGP unicasting are also available for MBGP.
The MBGP extensions specify that BGP can exchange information within different types
of address families. The address families available are unicast IPv4, multicast IPv4, and
VPN-IPv4. When you enable BGP, the router employs unicast IPv4 addresses by default.
We recommend you be thoroughly familiar with BGP before configuring MBGP. See
Configuring BGP Routing in the JunosE BGP and MPLS Configuration Guide for detailed
information about BGP and MBGP.
Investigating Multicast Routes
You can use the mtrace command to trace the path that multicast packets take from a
source to a destination through a multicast group address. This command is similar to
the traceroute command for investigating unicast routes.
mtrace
• Use to trace the path that multicast packets take to a destination.
• Specify the unicast IP address of the source for the packets.
• To direct the packets to a particular destination, specify the unicast address for that
destination. If you do not specify a destination, the router traces the route from the
device on which you issue the command.
• To direct the packets through a particular multicast group address, specify that
multicast group address. If you do not specify a multicast group address, the router
traces the route through the MBone audio multicast group.
39Copyright © 2010, Juniper Networks, Inc.
Chapter 1: Configuring IPv4 Multicast
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