Igmp Snooping - TRENDnet TI-PG1284i User Manual

TRENDnet User's Guide

IGMP Snooping

IGMP Snooping
The IGMP snooping is for multicast traffic. The Switch can passively snoop on IGMP
packets transferred between IP multicast routers/switches and IP multicast hosts to learn
the IP multicast group membership. It checks IGMP packets passing through it, picks out
the group registration information, and configures multicasting accordingly. IGMP
snooping allows the Switch to learn multicast groups without you having to manually
configure them.
The Switch can passively snoop on IGMP packets transferred between IP multicast
routers/switches and IP multicast hosts to learn the IP multicast group membership. It
checks IGMP packets passing through it, picks out the group registration information, and
configures multicasting accordingly. IGMP snooping allows the Switch to learn multicast
groups without you having to manually configure them.
The Switch forwards multicast traffic destined for multicast groups (that it has learned
from IGMP snooping or that you have manually configured) to ports that are members of
that group. IGMP snooping generates no additional network traffic, allowing you to
significantly reduce multicast traffic passing through your Switch.
The Switch can perform IGMP snooping on up to 4094 VLANs. You can configure the
Switch to automatically learn multicast group membership of any VLANs. The Switch then
performs IGMP snooping on the first VLANs that send IGMP packets. Alternatively, you
can specify the VLANs that IGMP snooping should be performed on. This is referred to as
fixed mode. In fixed mode the Switch does not learn multicast group membership of any
VLANs other than those explicitly added as an IGMP snooping VLAN.
Immediate Leave
When you enable IGMP Immediate-Leave processing, the switch
immediately removes a port when it detects an IGMP version 2 leave
message on that port. You should use the Immediate-Leave feature only
when there is a single receiver present on every port in the VLAN.
(
Immediate Leave is only supported on IGMP Version 2 hosts).
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The switch uses IGMP snooping Immediate Leave to remove from the forwarding table
an interface that sends a leave message without the switch sending group-specific queries
to the interface. The VLAN interface is pruned from the multicast tree for the multicast
group specified in the original leave message. Immediate Leave ensures optimal
bandwidth management for all hosts on a switched network, even when multiple
multicast groups are simultaneously in use.
Fast Leave
The switch allow user to configure a delay time. When the delay time is expired, the
switch removes the interface from the multicast group.
Last Member Query Interval
Last Member Query Interval: The Last Member Query Interval is the Max Response Time
inserted into Group-Specific Queries sent in response to Leave Group messages, and is
also the amount of time between Group-Specific Query messages.
Without Immediate Leave, when the switch receives an IGMP leave message from a
subscriber on a receiver port, it sends out an IGMP specific query on that port and waits
for IGMP group membership reports. If no reports are received in a configured time
period, the receiver port is removed from multicast group membership.
IGMP Querier
There is normally only one Querier per physical network. All multicast routers start up as
a Querier on each attached network. If a multicast router hears a Query message from a
router with a lower IP address, it MUST become a Non-Querier on that network. If a
router has not heard a Query message from another router for [Other Querier Present
Interval], it resumes the role of Querier. Routers periodically [Query Interval] send a
General Query on each attached network for which this router is the Querier, to solicit
membership information. On startup, a router SHOULD send [Startup Query Count]
General Queries spaced closely together [Startup Query Interval] in order to quickly and
reliably determine membership information. A General Query is addressed to the all-
systems multicast group (224.0.0.1), has a Group Address field of 0, and has a Max
Response Time of [Query Response Interval].
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