IE-SW-VL08M Series User’s Manual
Featured Functions
3-55
VLANs that are connected to it. For networks with more than one IP router, the router with the
lowest IP address is the querier. A switch with IP address lower than the IP address of any other
IGMP queriers connected to the LAN or VLAN can become the IGMP querier.
2.
When an IP host receives a query packet, it sends a
report
packet back that identifies the
multicast group that the end-station would like to join.
3.
When the report packet arrives at a port on a switch with
IGMP Snooping
enabled, the switch
knows that the port should forward traffic for the multicast group, and then proceeds to forward
the packet to the router.
4.
When the router receives the report packet, it registers that the LAN or VLAN requires traffic
for the multicast groups.
5.
When the router forwards traffic for the multicast group to the LAN or VLAN, the switches
only forward the traffic to ports that received a report packet.
GMRP (GARP Multicast Registration Protocol)
The IE-SW-VL08M supports IEEE 802.1D-1998 GMRP (GARP Multicast Registration Protocol),
which differs from IGMP (Internet Group Management Protocol). GMRP is a MAC-based multicast
management protocol, whereas IGMP is IP-based. GMRP provides a mechanism that allows bridges
and end stations to register or de-register Group membership information dynamically. GMRP
functions similarly to GVRP, except that GMRP registers multicast addresses on ports. When a port
receives a
GMRP-join
message, it will register the multicast address to its database if the multicast
address is not registered, and all the multicast packets with that multicast address are able to be
forwarded from this port. When a port receives a
GMRP-leave
message, it will de-register the
multicast address from its database, and all the multicast packets with this multicast address are not
able to be forwarded from this port.
Static Multicast MAC
Some devices may only support multicast packets, but not support either IGMP Snooping or GMRP.
The IE-SW-VL08M supports adding multicast groups manually to enable multicast filtering.
Enabling Multicast Filtering
Use the serial console or Web interface to enable or disable IGMP Snooping and IGMP querying. If
IGMP Snooping is not enabled, then IP multicast traffic is always forwarded, flooding the network.
Configuring IGMP Snooping
IGMP Snooping provides the ability to prune multicast traffic so that it travels only to those end
destinations that require that traffic, thereby reducing the amount of traffic on the Ethernet LAN.
IGMP Snooping Settings
IGMP Snooping Enable
Setting
Description
Factory Default
Enable/Disable
Select the option to enable the IGMP Snooping
function
globally
.
Disabled