OLT2406 User’s Guide
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CHAPTER 25
Multicast
25.1 Multicast Overview
This chapter shows you how to configure various multicast features.
Traditionally, IP packets are transmitted in one of either two ways - Unicast (1 sender to 1 recipient) or
Broadcast (1 sender to everybody on the network). Multicast delivers IP packets to just a group of hosts
on the network.
IGMP (Internet Group Management Protocol) is a network-layer protocol used to establish membership
in a multicast group - it is not used to carry user data. Refer to RFC 1112, RFC 2236 and RFC 3376 for
information on IGMP versions 1, 2 and 3 respectively.
25.1.1 What You Can Do
• Use the Multicast Status screen (Section 25.2 on page 199) to view multicast group information.
• Use the Multicast Setting screen (Section 25.3 on page 202) to configure multicast settings on the OLT.
• Use the IGMP Snooping VLAN screen (Section 25.3.1 on page 205) to perform IGMP snooping on up to
16 VLANs.
• Use the Mcast Channel screen (Section 25.3.2 on page 206) to configures a GPON client multicast
channel.
25.1.2 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).
IGMP Snooping
A OLT 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 OLT to learn multicast groups without you having to manually configure them.
The OLT 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
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