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Chapter 44 Multicast
XS3800-28 User’s Guide
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• Use the MLD Snooping-proxy Port Role Setting screen ( Section 44.9 on page 321 ) to assign MLD
snooping-proxy port roles and configure Leave settings for each port.
• Use the MLD Snooping-proxy Filtering screen ( Section 44.10 on page 323 ) to enable and configure
MLD snooping-proxy filtering.
• Use the MLD Snooping-proxy Filtering Profile screen ( Section 44.11 on page 325 ) to create/edit MLD
snooping-proxy filtering profiles.
44.1.3 What You Can Do – MVR
• Use the MVR screens ( Section 44.12 on page 327 ) to create multicast VLANs and select the receiver
ports and a source port for each multicast VLAN.
44.1.4 What You Need to Know
Read on for concepts on Multicasting that can help you configure the screens in this chapter.
IP Multicast Addresses
In IPv4, a multicast address allows a device to send packets to a specific group of hosts (multicast
group) in a different subnetwork. A multicast IP address represents a traffic receiving group, not
individual receiving devices. IP addresses in the Class D range (224.0.0.0 to 239.255.255.255) are used for
IP multicasting. Certain IP multicast numbers are reserved by IANA for special purposes (see the IANA
website for more information).
In IPv6, multicast addresses provide the same functionality as IPv4 broadcast addresses. Broadcasting is
not supported in IPv6. A multicast address allows a host to send packets to all hosts in a multicast group.
Multicast scope allows you to determine the size of the multicast group. A multicast address has a
predefined prefix of ff00::/8.
IGMP Filtering
With the IGMP filtering feature, you can control which IGMP groups a subscriber on a port can join. This
allows you to control the distribution of multicast services (such as content information distribution)
based on service plans and types of subscription.
You can set the Switch to filter the multicast group join reports on a per-port basis by configuring an
IGMP filtering profile and associating the profile to a port.
IGMP Snooping
A Switch can passively snoop on IGMP packets transferred between IP multicast routers or 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.