Rockwell Automation 1783-Mxxx Stratix 8000 and 8300 Ethernet Managed Switches User Manual - Manual (Page 69)

Rockwell Automation Publication 1783-UM003I-EN-P - March 2014 69
Switch Software Features Chapter 3
IGMP Snooping with Querier Layer 2 switches can use IGMP snooping to constrain the flooding of multicast
traffic by dynamically configuring Layer 2 interfaces so that multicast traffic is
forwarded to only those interfaces associated with IP multicast devices. As the
name implies, IGMP snooping requires the LAN switch to snoop on the IGMP
transmissions between the host and the router and to keep track of multicast
groups and member ports. When the switch receives an IGMP report from a host
for a particular multicast group, the switch adds the host port number to the
forwarding table entry; when it receives an IGMP Leave Group message from a
host, it removes the host port from the table entry. It also periodically deletes
entries if it does not receive IGMP membership reports from the multicast
clients.
The multicast router sends out periodic general queries to all VLANs. All hosts
interested in this multicast traffic send join requests and are added to the
forwarding table entry. The switch creates one entry per VLAN in the IGMP
snooping IP multicast forwarding table for each group from which it receives an
IGMP join request.
The switch supports IP multicast group-based bridging, rather than MAC-
addressed based groups. With multicast MAC address-based groups, if an IP
address being configured translates (aliases) to a previously configured MAC
address or to any reserved multicast MAC addresses (in the range 224.0.0.xxx),
the command fails. Because the switch uses IP multicast groups, there are no
address aliasing issues.
The default number of supported multicast groups are as follows:
• Stratix 8000 switch: 256
• Stratix 8300 switch: 1024
You can modify the number of multicast groups supported by using the
command line interface. If you have over 180 multicast groups on a Stratix 8000
we suggest modifying the number of multicast groups by changing the SDM
template to the Lanbase Routing template.
The IP multicast groups learned through IGMP snooping are dynamic. If you
specify group membership for a multicast group address statically, your setting
supersedes any automatic manipulation by IGMP snooping. Multicast group
membership lists can consist of both user-defined and IGMP snooping-learned
settings. Multicast IP addresses used by the EtherNet/IP network for I/O traffic
are learned by the switch.
IGMP implementation in the switch is IGMP V2. This version is
backward-compatible with switches running IGMP V1. The switch has a built in
querier function, and the global macro enables on IGMP Snooping and the
querier.