User Manual UMN:CLIV8102499Displaying Multicast Router PortTo display a current multicast router port for IGMP snooping, use the following command.Command Mode Descriptionshow ip igmp snooping mrouterEnableGlobalShows a current multicast router port for IGMP snoop-ing globally.show ip igmp snooping vlanVLANS mrouterShows a current multicast router port for IGMP snoop-ing on a specified VLAN.VLANS: VLAN ID (1-4094)10.2.3.8 TCN Multicast FloodingWhen a network topology change occurs, the protocols for a link layer topology – such asspanning tree protocol (STP), Ethernet ring protection (ERP), etc – notify switches in thetopology using a topology change notification (TCN).When TCN is received, the switch where an IGMP snooping is running will flood multicasttraffic to all ports in a VLAN, since a network topology change in a VLAN may invalidatepreviously learned IGMP snooping information. However, this flooding behavior is not de-sirable if the switch has many ports that are subscribed to different groups. The trafficcould exceed the capacity of the link between the switch and the end host, resulting inpacket loss. Thus, a period of multicast flooding needs to be controlled to solve such aproblem.Enabling TCN Multicast FloodingTo enable the switch to flood multicast traffic when TCN is received, use the followingcommand.Command Mode Descriptionip igmp snooping tcn floodGlobalEnables the switch to flood multicast traffic when TCNis received.ip igmp snooping tcn vlanVLANS floodEnables the switch to flood multicast traffic on a VLANwhen TCN is received.VLANS: VLAN ID (1-4094)To disable the switch to flood multicast traffic when TCN is received, use the followingcommand.Command Mode Descriptionno ip igmp snooping tcn floodGlobal Disables the switch to flood multicast traffic when TCNis receivedno ip igmp snooping tcn vlanVLANS flood
