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Configuration Guide - IP Multicast

S7700 and S9700 V200R013C00

This document describes the configurations of IP multicast, including IP multicast basics, IGMP, MLD, IPv4 PIM, IPv6 PIM, MSDP, multicast VPN, layer 3 multicast CAC, IPv4 multicast route management, IPv6 multicast route management, IGMP snooping, MLD snooping, static multicast MAC address, multicast VLAN replication, layer 2 multicast CAC, multicast network management.
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Multicast Addresses

Multicast Addresses

To enable multicast sources and group members to communicate, the network must provide network-layer multicast services using multicast IP addresses. Additionally, to enable multicast data to be correctly transmitted on the local physical network, the network must provide link-layer multicast services using multicast MAC addresses. The destination address of a multicast data packet is a group with unknown members but not a specific receiver. Therefore, multicast IP addresses must be mapped to multicast MAC addresses.

IPv4 Multicast Addresses

The Internet Assigned Numbers Authority (IANA) allocates Class D addresses for IPv4 multicast. An IPv4 address is 32 bits long, and the first four bits of a Class D IP address are 1110. Therefore, multicast IP addresses range from to Table 1-2 describes IPv4 multicast addresses.

Table 1-2  Range and description of IPv4 multicast addresses

Class D Address Range


Permanent multicast group addresses that are reserved by the IANA for routing protocols. The addresses identify a group of network devices and are not used for multicast forwarding. Table 1-3 lists the permanent multicast group addresses.

ASM group addresses that are valid on the entire network.

Default SSM group addresses that are valid on the entire network.

Administrative multicast addresses that are valid only in the local administrative domain. Different administrative domains can use the same administrative multicast addresses.

Table 1-3  List of permanent multicast group addresses

Permanent Multicast Group Addresses



All the hosts and routers on a network segment (similar to a broadcast address)

All multicast routers


Distance Vector Multicast Routing Protocol (DVMRP) routers

Open Shortest Path First (OSPF) routers

OSPF designated routers (DRs)

Shared tree (ST) routers

ST hosts

Routing Information Protocol version 2 (RIP-2) routers

Mobile agents

Dynamic Host Configuration Protocol (DHCP) servers or proxy agents

All Protocol Independent Multicast (PIM) routers

Resource Reservation Protocol (RSVP) encapsulation

Core-based tree (CBT) routers

Specified Subnetwork Bandwidth Management (SBM) device

All SBM devices

Virtual Router Redundancy Protocol (VRRP)

IGMPv3 routers


IPv6 Multicast Addresses

An IPv6 address is 128 bits long. The IPv6 multicast address format is defined in RFC 4291 and is shown in Figure 1-4.

Figure 1-4  IPv6 multicast address format

An IPv6 multicast address has a Group ID field to identify a multicast group.

  • FF: The leftmost eight bits are 11111111, indicating a multicast address. All IPv6 multicast addresses start with FF.

  • Flags: This field is 4 bits long and identifies the state of a multicast address.
    Table 1-4  Description of flag values




    Permanent multicast group addresses that are reserved by the IANA


    ASM group addresses


    ASM group addresses


    SSM group addresses



  • Scope: This field is 4 bits long and identifies the scope of a multicast group, for example, whether a multicast group covers nodes in the same network, same site, same organization or any node in the global address space.
    Table 1-5  Description of Scope field values



    0, 3, F



    Node/Interface-local scope


    Link-local scope


    Admin-Local scope


    Site-local scope


    Organization-local scope


    Global scope



  • Group ID: This field is 112 bits long and identifies a unique multicast group in the range specified by the Scope field. The Group ID can be permanently or temporarily assigned, depending on the value of the T flag in the Flags field.

Table 1-6 describes the IPv6 multicast address ranges.

Table 1-6  Range and description of IPv6 multicast addresses




Reserved group addresses (see Table 1-7).

FF1x::/32 (x is not 1 or 2)

FF2x::/32 (x is not 1 or 2)

ASM group addresses that are valid on the entire network.

FF3x::/32 (x is not 1 or 2)

Default SSM group address range. Addresses in this range are valid on the entire network.

Table 1-7  Commonly used IPv6 multicast addresses


IPv6 Multicast Addresses


Node/Interface-local scope


All node or interface addresses


All router addresses

Link-local scope


All node addresses


All router addresses


Unassigned addresses


DVMRP routers


OSPF IGP routers




ST routers


ST hosts


RIP routers


EIGRP routers


Mobile agents


All PIM routers


RSVP encapsulation


Link name


All DHCP proxy agents


Solicited-node addresses (XX:XXXX indicates the last 24 bits of a node IPv6 address)

Site-local scope


All router addresses


All DHCP servers


All DHCP relay agents


Service location

IPv4 Multicast MAC Addresses

When unicast IPv4 packets are transmitted on an Ethernet network, the packets use MAC addresses of receivers as destination MAC addresses. However, the destination of a multicast data packet is a group with changeable members but not a specific receiver. Therefore, multicast data packets must use IPv4 multicast MAC addresses on an Ethernet network. IPv4 multicast MAC addresses are link-layer addresses mapped from IPv4 multicast addresses.

As defined by the IANA, the leftmost 24 bits of an IPv4 multicast MAC address are 0x01005e, the 25th bit is 0, and the rightmost 23 bits are the same as the rightmost 23 bits of a multicast IPv4 address, as shown in Figure 1-5. Multicast MAC address 01-00-5e-00-01-01 is mapped to multicast IP address

Figure 1-5  Mapping between an IPv4 multicast address and an IPv4 multicast MAC address

The first four bits of an IPv4 multicast address are fixed as 1110, mapping the leftmost 25 bits of a multicast MAC address. Among the last 28 bits, only 23 bits are mapped to a MAC address, and 5 bits are lost. As a result, 32 multicast IP addresses are mapped to one MAC address. For example, multicast IP addresses,,, and are all mapped to multicast MAC address 01-00-5e-00-01-01. Address conflicts must be considered in address assignment.

IPv6 Multicast MAC Addresses

In an IPv6 multicast MAC address, the leftmost 16 bits are 0x3333, and the rightmost 32 bits are mapped to the rightmost 32 bits of an IPv6 multicast address. Figure 1-6 shows the mapping between IPv6 multicast address FF01::1111:1 and an IPv6 multicast MAC address.

Figure 1-6  Mapping between an IPv6 multicast address and an IPv6 multicast MAC address

The figure shows that more IPv6 multicast addresses are mapped to the same multicast MAC address.
Updated: 2019-04-08

Document ID: EDOC1100065742

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