Moxa EDR-810 User Manual download pdf (Page 36)

Industrial Secure Router User's Manual EDR-810 Series Features and Functions

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Snooping Mode

Snooping Mode allows your industrial secure router to forward multicast packets only to the appropriate ports.

The router snoops on exchanges between hosts and an IGMP device to find those ports that want to join a

multicast group, and then configures its filters accordingly.

Query Mode

Query mode allows the Moxa router 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 Moxa router to ensure proceeding query election. Enable query

mode to run multicast sessions on a network that does not contain IGMP routers (or queriers). Query mode

allows users to enable IGMP snooping by VLAN ID. Moxa industrial secure router support IGMP snooping

version 1, version 2 and version 3. Version 2 is compatible with version 1.The default setting is IGMP V1/V2. "

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. Moxa switches support IGMP version 1, 2 and 3. IGMP version 1 and 2 work as follows::

• 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.

• 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.

• 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.

• When the router receives the report packet, it registers that the LAN or VLAN requires traffic for the

multicast groups.

• 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.

IGMP version 3 supports “source filtering,” which allows the system to define how to treat packets from

specified source addresses. The system can either white-list or black-list specified sources.

IGMP version comparison

IGMP Version Main Features Reference

V1 a. Periodic query RFC-1112

V2 Compatible with V1 and adds:

a. Group-specific query

b. Leave group messages

c. Resends specific queries to verify leave message was the last one in

the group

d. Querier election

RFC-2236

V3 Compatible with V1, V2 and adds:

a. Source filtering

- accept multicast traffic from specified source

- accept multicast traffic from any source except the specified source

RFC-3376

Static Multicast MAC

Some devices may only support multicast packets, but not support either IGMP Snooping. The Moxa industrial

secure router supports adding multicast groups manually to enable multicast filtering.

Enabling Multicast Filtering

Use the USB 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.

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Moxa EDR-810 User Manual Page 36

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