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Chapter 24 Multicast
MGS3700-12C User’s Guide
240
24.1.3 IGMP Snooping
A 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.
24.1.4 IGMP Snooping and VLANs
The Switch can perform IGMP snooping on up to 16 VLANs. You can configure the
Switch to automatically learn multicast group membership of any VLANs. The
Switch then performs IGMP snooping on the first 16 VLANs that send IGMP
packets. This is referred to as auto mode. 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.
24.2 Multicast Status
Click Advanced Applications > Multicast to display the screen as shown. This
screen shows the multicast group information. See Section 24.1 on page 239 for
more information on multicasting.
Figure 111 Advanced Application > Multicast
The following table describes the labels in this screen.
Table 66 Advanced Application > Multicast Status
LABEL DESCRIPTION
Index This is the index number of the entry.
VID This field displays the multicast VLAN ID.
Port This field displays the port number that belongs to the multicast group.
Multicast Group This field displays IP multicast group addresses.