EDS-510A Series User’s Manual Featured Functions
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Query Mode
Query mode allows the EDS-510A to work as the Querier if it has the lowest IP address on the
subnetwork to which it belongs. IGMP querying is enabled by default on the EDS-510A to help
prevent interoperability issues with some multicast routers that may not follow the lowest IP
address election method. Enable query mode to run multicast sessions on a network that does not
contain IGMP routers (or queriers).
NOTE The EDS-510A is compatible with any device that conforms to the IGMP v2 and IGMP v3
device protocol.
IGMP Multicast Filtering IGMP is used by IP-supporting network devices to register hosts with multicast groups. It can be
used on all LANs and VLANs that contain a multicast capable IP router, and on other network
devices that support multicast filtering. IGMP works as follows:
1. The IP router (or querier) periodically sends query packets to all end-stations on the LANs or
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 EDS-510A 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 EDS-510A 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.