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Multicast
Configuring IGMP Snooping
STEP 4
STEP 5
Configuring IGMP Snooping
Cisco Small Business SG200 Series 8-port Smart Switch
Set the type to indicate whether the entry is statically configured or dynamically
learned. Ports can become members of a particular MAC address group
dynamically through the exchange of IGMP packets, or you can statically configure
them as members.
Click Apply. Your changes are saved to the Running Configuration.
Internet Group Management Protocol (IGMP) is a layer 3 Internet protocol that
enables IPv4 networks to manage memberships to multicast groups. (IPv6
multicast traffic is managed using the MLD protocol, as described in
MLD
Snooping.) IGMP communication occurs between IGMP routers and IGMP-
enabled hosts (clients). Although the switch does not initiate or reply to IGMP
packets, it can be configured to listen to IGMP communication between routers
and clients that are connected by the switch, and to make forwarding decisions
that help to reduce unnecessary network traffic.This listening behavior is referred
to as IGMP snooping. This is particularly beneficial for high-bandwidth multicast
network traffic.
Ordinarily, when the switch receives broadcast or multicast packets, the switch
forwards a copy into each of the remaining network segments. This approach
works well for broadcast packets that are intended to be processed by all
connected nodes. For multicast packets, however, this approach could lead to less
efficient use of network bandwidth, particularly when the packet is intended for
only a small number of nodes; packets are flooded into network segments where
no node has an interest in receiving the packet.
IGMP snooping enables the switch to intercept membership reports from IGMP
clients and queries from routers. If the intercepted communications indicate that
no IGMP clients exist on a link for a particular multicast destination address within
a VLAN, then the switch does not send copies of those multicast packets to that
network segment.
IGMP snooping can be enabled or disabled on each VLAN. When enabled on a
VLAN, IGMP snooping is performed on all interfaces that are members of that
VLAN.
Although IGMP is based on IP multicast addresses, the switch performs the actual
multicast forwarding based on the equivalent MAC addresses.
8
Configuring
136
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