User Manual

494
Users Manual of XGS-6350-24X4C
show ip mroute mfc Displays the multicast forwarding cache.
show ip rpf [ucast | mstatic | pim-dm
| pim-sm | dvmrp] source-address
Displays the RPF information.
IGMP Configuration
50.3
50.3.1 Overview
50.3.1.1 IGMP
Internet Group Management Protocol (IGMP) is a protocol used to manage multicast group members. IGMP
is an asymmetric protocol, containing the host side and the switch side. At the host side, the IGMP protocol
regulates how the host, the multicast group member, reports the multicast group it belongs to and how the
host responds to the query message from the switch. At the switch side, the IGMP protocol regulates how the
IGMP-supported switch learns the multicast group member ID of the hosts in the local network and how to
modify the stored multicast group member information according to the report message from the host.
Since our switches support the IGMP Router protocol, the multicast routing protocol can be provided with the
information about the multicast group members in the current network and the switch decides whether to
forward the multicast message. In a word, to enable the switch support the multicast process of the IP
message, the switch need be configured to support the multicast routing protocol and the IGMP Router
protocol. Currently, MY COMPANY' switches support the IGMP Router protocol and version 3 IGMP, the latest
version.
There is no independent startup commands for IGMP. The function of the IGMP-Router protocol is started up
through the multicast routing protocol.
50.3.1.2 OLNK
Strictly speaking, the IGMP only-link protocol (OLNK) is not a multicast routing protocol because it has no
interaction process as other protocols. However, in some special cases, running OLNK in the simple topology
will get nice results. Similar to the PIM-DM protocol which also has no negotiation process, OLNK can handle
the change of IGMP group members and promptly adjust the RPF interface according to the topology change.
In this way, OLNK ensures the multicast forwarding and prevents the control messages of the multicast
routing protocol from occupying the bandwidth.
50.3.2 IGMP Configuration
The commands to configure the attributes of the IGMP-Router mainly are the commands to adjust the IGMP
parameters. The following is to describe these commands. For details about these commands, refer to
explanation documents relative to the IGMP commands.
50.3.2.1 Changing Current IGMP Version
Up to now, the IGMP protocol has three formal versions. The corresponding RFCs are RFC1112, RFC2236