3Com 10014298 manual Configuring Igmp, Displaying and Debugging Common Multicast Configuration

116CHAPTER 6: MULTICAST PROTOCOL

Displaying and Debugging Common Multicast Configuration

After the previous configurations, execute the display command to view the multicast configuration, and to verify the configuration.

Execute debugging command in user view for the debugging of multicast.

Table 120 Display and Debug Common Multicast Configuration

Operation	Command
Display the multicast routing table	display multicast routing-table [
	group-address [ mask { mask
	mask-length } ] source-address
	[ mask { mask mask-length } ]
	incoming-interface {
	interface-type interface-number
	register } ]*
Display the multicast forwarding table	display multicast
	forwarding-table [ group-address
	[ mask { mask mask-length } ]
	source-address [ mask { mask
	mask-length } ]
	incoming-interface register } ]*
Display the RPF routing information	display multicast rpf-info
	source-address
Enable multicast packet forwarding	debugging multicast forwarding
debugging
Disable multicast packet forwarding	undo debugging multicast
debugging	forwarding
Enable multicast forwarding status debugging	debugging multicast-status
	forwarding
Disable multicast forwarding status debugging	undo debugging multicast-status
	forwarding
Enable multicast kernel routing debugging	debugging multicast
	kernel-routing
Disable multicast kernel routing debugging	undo debugging multicast
	kernel-routing

Configuring IGMP	IGMP (Internet Group Management Protocol) is a protocol, in the TCP/IP suite,
	responsible for management of IP multicast members. It is used to establish and
	maintain multicast membership among IP hosts and their connected neighboring
	routers. IGMP excludes transmitting and maintenance information among
	multicast routers, which are completed by multicast routing protocols. All hosts
	participating in multicast must implement IGMP.
	Hosts participating in multicast can join or leave a multicast group at any time, in
	any place, and without limitation of member numbers. A multicast router does not
	need and cannot keep the membership of all hosts. It only uses IGMP to learn
	whether receivers (i.e., group members) of a multicast group are present on the
	subnet connected to each interface. A host only needs to keep the multicast
	groups it has joined.
	IGMP is not symmetric on hosts and routers. Hosts need to respond to IGMP query
	messages from the multicast router, i.e., report the group membership to the
	router. The router needs to send membership query messages periodically to