User Manual User Manual

Rockwell Automation Publication 1783-UM001D-EN-P - January 2013 25
Network Services Setup Chapter 2
IGMP
Internet Group Management Protocol (IGMP) snooping sorts multicasting
devices into groups. This limits the multicast packets received by hosts that do
not need the information and makes the network more efficient and
deterministic.
By default, IGMP is disabled. Enable IGMP snooping when I/O is running on
your network. IGMP helps to isolate this UDP traffic to ports that need to
receive it. When it is not used, other devices may be slowed down by the
continuous flow of UDP packets.
IGMP Product Support
Rockwell Automation products support IGMP, version 2.
When using the Logix Designer application to configure your switch, consider
the following:
• Settings on the IGMP page in the Add-on Profile overwrite settings made
on the web management interface.
• If you are scanning the 1783-EMS switch with the Logix Designer
application, use the IGMP page in the Add-on Profile to configure IGMP
to avoid confusion. See Appendix E
for more information.
The switch manages a report of IGMP information, including multicast groups,
querier information, and IGMP states per virtual local-area network (VLAN).
The report is available through the web interface. For more information about
this report, refer to IGMP Report
on page 45.
Option Description
Broadcast Without IGMP snooping, an I/O module acts like a broadcasting device and all
devices on the subnet are flooded with I/O traffic.
Multicast IGMP snooping filters the I/O traffic from devices that are not in the intended
multicast group.
Unicast A message instruction from one Logix controller to another is an example of
unicast; it contains one source and one destination address.