428
Configuring IGMP Snooping and MVR
Information About IGMP Snooping and MVR
Figure 66
Second Host Joining a Multicast Group
Leaving a Multicast Group
The router sends periodic multicast general queries, and the switch forwards these queries through all ports in the VLAN.
Interested hosts respond to the queries. If at least one host in the VLAN wishes to receive multicast traffic, the router
continues forwarding the multicast traffic to the VLAN. The switch forwards multicast group traffic only to those hosts
listed in the forwarding table for that IP multicast group maintained by IGMP snooping.
When hosts want to leave a multicast group, they can silently leave, or they can send a leave message. When the switch
receives a leave message from a host, it sends a group-specific query to learn if any other devices connected to that
interface are interested in traffic for the specific multicast group. The switch then updates the forwarding table for that
MAC group so that only those hosts interested in receiving multicast traffic for the group are listed in the forwarding table.
If the router receives no reports from a VLAN, it removes the group for the VLAN from its IGMP cache.
Immediate Leave
Immediate Leave is only supported on IGMP Version 2 hosts.
The switch uses IGMP snooping Immediate Leave to remove from the forwarding table an interface that sends a leave
message without the switch sending group-specific queries to the interface. The VLAN interface is pruned from the
multicast tree for the multicast group specified in the original leave message. Immediate Leave ensures optimal
bandwidth management for all hosts on a switched network, even when multiple multicast groups are simultaneously in
use.
Note:
You should only use the Immediate Leave feature on VLANs where a single host is connected to each port. If
Immediate Leave is enabled in VLANs where more than one host is connected to a port, some hosts might inadvertently
be dropped.
When you enable IGMP Immediate Leave, the switch immediately removes a port when it detects an IGMP Version 2 leave
message on that port. You should only use the Immediate-Leave feature when there is a single receiver present on every
port in the VLAN.
Destination Address
Type of Packet
Ports
224.1.2.3
IGMP
1, 2, 5
Forwarding
table
CPU
Host 1
Host 2
Host 3
Host 4
Router A
PFC
VLAN
1
0
2
3
4
5
45751
Содержание IE 4000
Страница 12: ...8 Configuration Overview Default Settings After Initial Switch Configuration ...
Страница 52: ...48 Configuring Interfaces Monitoring and Maintaining the Interfaces ...
Страница 108: ...104 Configuring Switch Clusters Additional References ...
Страница 128: ...124 Performing Switch Administration Additional References ...
Страница 130: ...126 Configuring PTP ...
Страница 140: ...136 Configuring CIP Additional References ...
Страница 146: ...142 Configuring SDM Templates Configuration Examples for Configuring SDM Templates ...
Страница 192: ...188 Configuring Switch Based Authentication Additional References ...
Страница 244: ...240 Configuring IEEE 802 1x Port Based Authentication Additional References ...
Страница 274: ...270 Configuring SGT Exchange Protocol over TCP SXP and Layer 3 Transport Configuring Cisco TrustSec Caching ...
Страница 298: ...294 Configuring VLANs Additional References ...
Страница 336: ...332 Configuring STP Additional References ...
Страница 408: ...404 Configuring DHCP Additional References ...
Страница 450: ...446 Configuring IGMP Snooping and MVR Additional References ...
Страница 490: ...486 Configuring SPAN and RSPAN Additional References ...
Страница 502: ...498 Configuring Layer 2 NAT ...
Страница 559: ...555 Configuring Network Security with ACLs How to Configure Network Security with ACLs Creating a Numbered Extended ACL ...
Страница 770: ...766 Configuring IPv6 MLD Snooping Related Documents ...
Страница 930: ...926 Configuring IP Unicast Routing Related Documents ...
Страница 956: ...952 Configuring IPv6 Unicast Routing Configuring IPv6 network 2010 AB8 2 48 network 2010 AB8 3 48 exit address family ...
Страница 976: ...972 Configuring Cisco IOS IP SLAs Operations Additional References ...
Страница 978: ...974 Dying Gasp ...
Страница 990: ...986 Configuring Enhanced Object Tracking Monitoring Enhanced Object Tracking ...
Страница 994: ...990 Configuring MODBUS TCP Displaying MODBUS TCP Information ...
Страница 996: ...992 Ethernet CFM ...
Страница 1030: ...1026 Working with the Cisco IOS File System Configuration Files and Software Images Working with Software Images ...
Страница 1066: ...1062 Using an SD Card SD Card Alarms ...