8- and 24-Port Gigabit L2 Managed Power-over-Ethernet (PoE) Switches
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4.17 Multicast
This function establishes which multicast groups forward the multicast packet to the member ports. This avoids wasting the
bandwidth while IP multicast packets are running over the network. This is because a switch that does not support IGMP or
IGMP Snooping cannot tell the multicast packet from the broadcast packet, so it can only treat them all as broadcast packets.
Without IGMP Snooping, the multicast packet forwarding function functions in the same way as broadcast packet forwarding.
A switch supports IGMP Snooping with query, report and leave. A type of packet exchanged between IP Multicast
Router/Switch and IP Multicast Host, can update the Multicast table’s information when a member (port) joins or leaves an IP
Multicast Destination Address. Once a switch receives an IP multicast packet, it will forward the packet to the members who
were joined in a specified IP multicast group.
The packets will be discarded by the IGMP Snooping if the user transmits multicast packets to the multicast group that was
not built in advance.
4.17.1 IGMP Mode
Function name:
IGMP Mode Configuration
Function description:
IGMP mode enables the switch to issue the IGMP function. This enables IGMP proxy or snooping on the
switch, which connects to a router closer to the root of the tree. This interface is the
upstream
interface
. The router on the
upstream interface should be running IGMP.
Figure 4-159. IGMP Mode.
Parameter description:
IGMP Mode: Choose the IGMP mode “Disable,” “Proxy,” or “Snooping,’ from the drop-down menu.
4.17.2 IGMP Proxy
Function name: IGMP Proxy Configuration
Function description: IGMP proxy enables the switch to issue IGMP host messages on behalf of hosts that the system discovered
through standard IGMP interfaces. The switch acts as a
proxy
for its hosts.
Enable IGMP proxy on the switch, which connects to a router closer to the root of the tree. This interface is the upstream interface.
The router on the upstream interface should be running IGMP.