HP VSR1000 User manual

HPE VSR1000 Virtual Services Router
IP Multicast Configuration Guide
Part number: 5200-3152
Software version: VSR1000_HPE-CMW710-E0518-X64
Document version: 5W100-20170314

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Contents
Multicast overview··························································································· 1
Introduction to multicast ·····································································································································1
Information transmission techniques··········································································································1
Multicast features ·······································································································································3
Common notations in multicast ··················································································································4
Multicast benefits and applications ············································································································4
Multicast models ················································································································································4
Multicast architecture ·········································································································································5
Multicast addresses ···································································································································5
Multicast protocols ·····································································································································9
Multicast packet forwarding mechanism ··········································································································11
Multicast support for VPNs ······························································································································11
Introduction to VPN instances··················································································································11
Multicast application in VPNs···················································································································12
Configuring multicast routing and forwarding················································ 13
Overview ··························································································································································13
RPF check mechanism ····························································································································13
Static multicast routes ······························································································································15
Multicast forwarding across unicast subnets····························································································16
Configuration task list·······································································································································17
Enabling IP multicast routing ···························································································································17
Configuring multicast routing and forwarding···································································································18
Configuring static multicast routes ···········································································································18
Specifying the longest prefix match principle ···························································································18
Configuring multicast load splitting···········································································································19
Configuring a multicast forwarding boundary···························································································19
Delivering packets that fail the RPF check to the CPU ············································································19
Displaying and maintaining multicast routing and forwarding ··········································································20
Multicast routing and forwarding configuration examples ················································································22
Changing an RPF route ···························································································································22
Creating an RPF route ·····························································································································24
Multicast forwarding over a GRE tunnel···································································································26
Multicast forwarding over ADVPN tunnels ·······························································································28
Troubleshooting multicast routing and forwarding ···························································································34
Static multicast route failure ·····················································································································34
Configuring IGMP ························································································· 36
Overview ··························································································································································36
IGMPv1 overview ·····································································································································36
IGMPv2 enhancements····························································································································37
IGMPv3 enhancements····························································································································38
IGMP SSM mapping ································································································································39
IGMP proxying ·········································································································································40
Multicast access control ···························································································································41
IGMP support for VPNs····························································································································41
Protocols and standards ··························································································································42
IGMP configuration task list ·····························································································································42
Configuring basic IGMP features ·····················································································································42
Enabling IGMP ·········································································································································42
Specifying an IGMP version·····················································································································43
Configuring a static group member ··········································································································43
Configuring a multicast group policy ········································································································44
Adjusting IGMP performance···························································································································44
Configuring IGMP query and response parameters·················································································44
Enabling fast-leave processing ················································································································46
Configuring IGMP SSM mappings ···················································································································47

ii
Configuration prerequisites ······················································································································47
Configuration procedure···························································································································47
Configuring IGMP proxying······························································································································47
Configuration prerequisites ······················································································································47
Enabling IGMP proxying ··························································································································48
Enabling multicast forwarding on a non-querier interface ········································································48
Configuring multicast load splitting on an IGMP proxy·············································································49
Configuring multicast access control ···············································································································49
Configuration prerequisites ······················································································································49
Enabling multicast access control ············································································································49
Configuring an IGMP user access policy ·································································································50
Enabling per-session multicast forwarding·······························································································50
Configuring a VLAN-based static group member·····················································································51
Displaying and maintaining IGMP····················································································································52
IGMP configuration examples··························································································································52
Basic IGMP features configuration examples ··························································································52
IGMP SSM mapping configuration example ····························································································54
IGMP proxying configuration example ·····································································································57
Multicast access control configuration example (for PPPoE)···································································59
Multicast access control configuration example (for IPoE) ······································································63
Multicast access control configuration example (for Portal)·····································································68
Troubleshooting IGMP ·····································································································································73
No membership information on the receiver-side router ··········································································73
Inconsistent membership information on the routers on the same subnet···············································73
Configuring PIM ···························································································· 74
Overview ··························································································································································74
PIM-DM overview·····································································································································74
PIM-SM overview ·····································································································································76
BIDIR-PIM overview·································································································································82
Administrative scoping overview ··············································································································85
PIM-SSM overview···································································································································87
Relationship among PIM protocols ··········································································································88
PIM support for VPNs ······························································································································89
Protocols and standards ··························································································································89
Configuring PIM-DM ········································································································································89
PIM-DM configuration task list ·················································································································90
Configuration prerequisites ······················································································································90
Enabling PIM-DM ·····································································································································90
Enabling the state refresh feature ············································································································90
Configuring state refresh parameters·······································································································91
Configuring PIM-DM graft retry timer ·······································································································91
Configuring PIM-SM·········································································································································92
PIM-SM configuration task list··················································································································92
Configuration prerequisites ······················································································································92
Enabling PIM-SM ·····································································································································92
Configuring an RP····································································································································93
Configuring a BSR ···································································································································95
Configuring multicast source registration ·································································································97
Configuring the switchover to SPT···········································································································98
Configuring BIDIR-PIM ····································································································································98
BIDIR-PIM configuration task list ·············································································································99
Configuration prerequisites ······················································································································99
Enabling BIDIR-PIM ·································································································································99
Configuring an RP··································································································································100
Configuring a BSR ·································································································································102
Configuring PIM-SSM ····································································································································104
PIM-SSM configuration task list ·············································································································104
Configuration prerequisites ····················································································································104
Enabling PIM-SM ···································································································································104
Configuring the SSM group range··········································································································105
Configuring common PIM features ················································································································105

iii
Configuration task list·····························································································································105
Configuration prerequisites ····················································································································105
Configuring a multicast source policy·····································································································106
Configuring a PIM hello policy················································································································106
Configuring PIM hello message options·································································································106
Configuring common PIM timers············································································································108
Setting the maximum size of a join or prune message ··········································································109
Enabling BFD for PIM ····························································································································109
Enabling PIM passive mode···················································································································110
Enabling SNMP notifications for PIM ·····································································································110
Enabling NBMA mode for ADVPN tunnel interfaces··············································································111
Displaying and maintaining PIM·····················································································································111
PIM configuration examples···························································································································112
PIM-DM configuration example··············································································································112
PIM-SM non-scoped zone configuration example ·················································································115
PIM-SM admin-scoped zone configuration example··············································································118
BIDIR-PIM configuration example··········································································································123
PIM-SSM configuration example············································································································127
Troubleshooting PIM······································································································································130
A multicast distribution tree cannot be correctly built ·············································································130
Multicast data is abnormally terminated on an intermediate router························································131
An RP cannot join an SPT in PIM-SM····································································································131
An RPT cannot be built or multicast source registration fails in PIM-SM ···············································131
Configuring multicast VPN ·········································································· 133
Overview ························································································································································133
MD VPN overview ··································································································································134
Protocols and standards ························································································································137
How MD VPN works·······································································································································137
Default-MDT establishment····················································································································138
Default-MDT-based delivery ··················································································································141
MDT switchover ·····································································································································144
Inter-AS MD VPN ···································································································································145
M6VPE ···················································································································································148
Multicast VPN configuration task list ··············································································································149
Configuring MD VPN······································································································································150
Configuration prerequisites ····················································································································150
Enabling IP multicast routing for a VPN instance···················································································150
Creating an MD for a VPN instance ·······································································································151
Create an MD address family·················································································································151
Specifying the default-group ··················································································································151
Specifying the MD source interface ·······································································································152
Configuring MDT switchover parameters·······························································································152
Configuring the RPF vector feature········································································································153
Enabling data-group reuse logging ········································································································154
Configuring BGP MDT ···································································································································154
Configuration prerequisites ····················································································································154
Configuring BGP MDT peers or peer groups ·························································································155
Configuring a BGP MDT route reflector ·································································································155
Displaying and maintaining multicast VPN ····································································································156
Multicast VPN configuration examples ··········································································································157
Intra-AS MD VPN configuration example·······························································································157
Intra-AS M6VPE configuration example·································································································170
MD VPN inter-AS option B configuration example·················································································185
MD VPN inter-AS option C configuration example·················································································198
Troubleshooting MD VPN ······························································································································211
A default-MDT cannot be established ····································································································211
An MVRF cannot be created··················································································································212
Configuring IPv6 multicast routing and forwarding······································ 213
Overview ························································································································································213
RPF check mechanism ··························································································································213

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IPv6 multicast forwarding across IPv6 unicast subnets ·········································································215
Configuration task list·····································································································································215
Enabling IPv6 multicast routing······················································································································215
Configuring IPv6 multicast routing and forwarding ························································································216
Specifying the longest prefix match principle ·························································································216
Configuring IPv6 multicast load splitting ································································································216
Configuring an IPv6 multicast forwarding boundary···············································································217
Delivering packets that fail the RPF check to the CPU ··········································································217
Displaying and maintaining IPv6 multicast routing and forwarding ································································218
IPv6 multicast routing and forwarding configuration examples······································································220
IPv6 multicast forwarding over a GRE tunnel ························································································220
IPv6 multicast forwarding over ADVPN tunnel interfaces ······································································222
Configuring MLD ························································································· 230
Overview ························································································································································230
How MLDv1 works ·································································································································230
MLDv2 enhancements ···························································································································232
MLD SSM mapping ································································································································233
MLD proxying ·········································································································································234
IPv6 multicast access control·················································································································234
MLD support for VPNs ···························································································································235
Protocols and standards ························································································································235
MLD configuration task list·····························································································································235
Configuring basic MLD features·····················································································································235
Enabling MLD·········································································································································236
Specifying an MLD version ····················································································································236
Configuring a static group member ········································································································236
Configuring an IPv6 multicast group policy ····························································································237
Adjusting MLD performance ··························································································································237
Configuring MLD query and response parameters ················································································237
Enabling fast-leave processing ··············································································································239
Configuring MLD SSM mappings···················································································································240
Configuration prerequisites ····················································································································240
Configuration procedure·························································································································240
Configuring MLD proxying ·····························································································································240
Configuration prerequisites ····················································································································240
Enabling MLD proxying ··························································································································241
Enabling IPv6 multicast forwarding on a non-querier interface······························································241
Configuring IPv6 multicast load splitting on an MLD proxy ····································································241
Configuring IPv6 multicast access control ·····································································································242
Configuration prerequisites ····················································································································242
Enabling IPv6 multicast access control··································································································242
Configuring an MLD user access policy·································································································242
Enabling per-session IPv6 multicast forwarding ····················································································243
Configuring a VLAN-based static group member···················································································244
Displaying and maintaining MLD ···················································································································245
MLD configuration examples ·························································································································245
Basic MLD features configuration examples··························································································245
MLD SSM mapping configuration example····························································································247
MLD proxying configuration example·····································································································250
IPv6 multicast access control configuration example (for PPPoE) ························································252
IPv6 multicast access control configuration example (for IPoE) ····························································256
IPv6 multicast access control configuration example (for Portal)···························································261
Troubleshooting MLD·····································································································································266
No member information exists on the receiver-side router ····································································266
Inconsistent membership information on the routers on the same subnet·············································266
Configuring IPv6 PIM ·················································································· 267
Overview ························································································································································267
IPv6 PIM-DM overview···························································································································267
IPv6 PIM-SM overview···························································································································269
IPv6 BIDIR-PIM overview·······················································································································275

v
IPv6 administrative scoping overview ····································································································278
IPv6 PIM-SSM overview ························································································································280
Relationship among IPv6 PIM protocols ································································································281
IPv6 PIM support for VPNs ····················································································································282
Protocols and standards ························································································································282
Configuring IPv6 PIM-DM ······························································································································282
IPv6 PIM-DM configuration task list ·······································································································283
Configuration prerequisites ····················································································································283
Enabling IPv6 PIM-DM···························································································································283
Enabling the state refresh feature ··········································································································283
Configuring state refresh parameters·····································································································284
Configuring IPv6 PIM-DM graft retry timer ·····························································································284
Configuring IPv6 PIM-SM ······························································································································285
IPv6 PIM-SM configuration task list ·······································································································285
Configuration prerequisites ····················································································································285
Enabling IPv6 PIM-SM ···························································································································285
Configuring an RP··································································································································286
Configuring a BSR ·································································································································288
Configuring IPv6 multicast source registration·······················································································290
Configuring the switchover to SPT·········································································································291
Configuring IPv6 BIDIR-PIM ··························································································································291
IPv6 BIDIR-PIM configuration task list ···································································································291
Configuration prerequisites ····················································································································292
Enabling IPv6 BIDIR-PIM·······················································································································292
Configuring an RP··································································································································293
Configuring a BSR ·································································································································295
Configuring IPv6 PIM-SSM ····························································································································297
IPv6 PIM-SSM configuration task list ·····································································································297
Configuration prerequisites ····················································································································297
Enabling IPv6 PIM-SM ···························································································································297
Configuring the IPv6 SSM group range ·································································································298
Configuring common IPv6 PIM features ········································································································298
Configuration task list·····························································································································298
Configuration prerequisites ····················································································································298
Configuring an IPv6 multicast source policy ··························································································299
Configuring an IPv6 PIM hello policy ·····································································································299
Configuring IPv6 PIM hello message options ························································································299
Configuring common IPv6 PIM timers····································································································301
Setting the maximum size of a join or prune message ··········································································302
Enabling BFD for IPv6 PIM ····················································································································302
Enabling IPv6 PIM passive mode ··········································································································303
Enabling SNMP notifications for IPv6 PIM ·····························································································303
Enabling NBMA mode for IPv6 ADVPN tunnel interfaces······································································304
Displaying and maintaining IPv6 PIM ············································································································304
IPv6 PIM configuration examples ··················································································································305
IPv6 PIM-DM configuration example······································································································305
IPv6 PIM-SM non-scoped zone configuration example ·········································································308
IPv6 PIM-SM admin-scoped zone configuration example ·····································································311
IPv6 BIDIR-PIM configuration example··································································································317
IPv6 PIM-SSM configuration example ···································································································321
Troubleshooting IPv6 PIM······························································································································324
A multicast distribution tree cannot be correctly built ·············································································324
IPv6 multicast data is abnormally terminated on an intermediate router ···············································324
An RP cannot join an SPT in IPv6 PIM-SM ···························································································325
An RPT cannot be built or IPv6 multicast source registration fails in IPv6 PIM-SM·······························325
Document conventions and icons ······························································· 326
Conventions ···················································································································································326
Network topology icons··································································································································327
Support and other resources ······································································ 328
Accessing Hewlett Packard Enterprise Support ····························································································328

vi
Accessing updates·········································································································································328
Websites ················································································································································329
Customer self repair·······························································································································329
Remote support······································································································································329
Documentation feedback ·······················································································································329
Index ··········································································································· 331

1
Multicast overview
Introduction to multicast
As a technique that coexists with unicast and broadcast, the multicast technique effectively
addresses the issue of point-to-multipoint data transmission. By enabling high-efficiency
point-to-multipoint data transmission over a network, multicast greatly saves network bandwidth and
reduces network load.
By using multicast technology, a network operator can easily provide bandwidth-critical and
time-critical information services. These services include live webcasting, Web TV, distance learning,
telemedicine, Web radio, and real-time video conferencing.
Information transmission techniques
The information transmission techniques include unicast, broadcast, and multicast.
Unicast
In unicast transmission, the information source must send a separate copy of information to each
host that needs the information.
Figure 1 Unicast transmission
In Figure 1, Host B, Host D, and Host E need the information. A separate transmission channel must
be established from the information source to each of these hosts.
In unicast transmission, the traffic transmitted over the network is proportional to the number of hosts
that need the information. If a large number of hosts need the information, the information source
must send a separate copy of the same information to each of these hosts. Sending many copies
can place a tremendous pressure on the information source and the network bandwidth.
Unicast is not suitable for batch transmission of information.
Source
Receiver
Receiver
Receiver
Host A
Host B
Host C
Host D
Host E
Packets for Host B
Packets for Host D
Packets for Host E
IP network

2
Broadcast
In broadcast transmission, the information source sends information to all hosts on the subnet, even
if some hosts do not need the information.
Figure 2 Broadcast transmission
In Figure 2, only Host B, Host D, and Host E need the information. If the information is broadcast to
the subnet, Host A and Host C also receive it. In addition to information security issues, broadcasting
to hosts that do not need the information also causes traffic flooding on the same subnet.
Broadcast is disadvantageous in transmitting data to specific hosts. Moreover, broadcast
transmission is a significant waste of network resources.
Multicast
Multicast provides point-to-multipoint data transmissions with the minimum network consumption.
When some hosts on the network need multicast information, the information sender, or multicast
source, sends only one copy of the information. Multicast distribution trees are built through multicast
routing protocols, and the packets are replicated only on nodes where the trees branch.

3
Figure 3 Multicast transmission
In Figure 3, the multicast source sends only one copy of the information to a multicast group. Host B,
Host D, and Host E, which are information receivers, must join the multicast group. The routers on
the network duplicate and forward the information based on the distribution of the group members.
Finally, the information is correctly delivered to Host B, Host D, and Host E.
To summarize, multicast has the following advantages:
•Advantages over unicast—Multicast data is replicated and distributed until it flows to the
farthest-possible node from the source. The increase of receiver hosts will not remarkably
increase the load of the source or the usage of network resources.
•Advantages over broadcast—Multicast data is sent only to the receivers that need it. This
saves network bandwidth and enhances network security. In addition, multicast data is not
confined to the same subnet.
Multicast features
•A multicast group is a multicast receiver set identified by an IP multicast address. Hosts must
join a multicast group to become members of the multicast group before they receive the
multicast data addressed to that multicast group. Typically, a multicast source does not need to
join a multicast group.
•A multicast source is an information sender. It can send data to multiple multicast groups at the
same time. Multiple multicast sources can send data to the same multicast group at the same
time.
•The group memberships are dynamic. Hosts can join or leave multicast groups at any time.
Multicast groups are not subject to geographic restrictions.
•Multicast routers or Layer 3 multicast devices are routers or Layer 3 switches that support Layer
3 multicast. They provide multicast routing and manage multicast group memberships on stub
subnets with attached group members. A multicast router itself can be a multicast group
member.
For a better understanding of the multicast concept, you can compare multicast transmission to the
transmission of TV programs.

4
Table 1 Comparing TV program transmission and multicast transmission
TV program transmission Multicast transmission
A TV station transmits a TV program through a
channel.
A multicast source sends multicast data to a multicast
group.
A user tunes the TV set to the channel. A receiver joins the multicast group.
The user starts to watch the TV program
transmitted by the TV station on the channel.
The receiver starts to receive the multicast data sent by
the source to the multicast group.
The user turns off the TV set or tunes to another
channel.
The receiver leaves the multicast group or joins another
group.
Common notations in multicast
The following notations are commonly used in multicast transmission:
•(*, G)—Rendezvous point tree (RPT), or a multicast packet that any multicast source sends to
multicast group G. The asterisk (*) represents any multicast source, and "G" represents a
specific multicast group.
•(S, G)—Shortest path tree (SPT), or a multicast packet that multicast source "S" sends to
multicast group "G." "S" represents a specific multicast source, and "G" represents a specific
multicast group.
For more information about the concepts RPT and SPT, see "Configuring PIM"and "Configuring
IPv6 PIM."
Multicast benefits and applications
Multicast benefits
•Enhanced efficiency—Reduces the processor load of information source servers and network
devices.
•Optimal performance—Reduces redundant traffic.
•Distributed application—Enables point-to-multipoint applications at the price of minimum
network resources.
Multicast applications
•Multimedia and streaming applications, such as Web TV, Web radio, and real-time video/audio
conferencing
•Communication for training and cooperative operations, such as distance learning and
telemedicine
•Data warehouse and financial applications (stock quotes)
•Any other point-to-multipoint application for data distribution
Multicast models
Based on how the receivers treat the multicast sources, the multicast models include any-source
multicast (ASM), source-filtered multicast (SFM), and source-specific multicast (SSM).

5
ASM model
In the ASM model, any multicast sources can send information to a multicast group. Receivers can
join a multicast group and get multicast information addressed to that multicast group from any
multicast sources. In this model, receivers do not know the positions of the multicast sources in
advance.
SFM model
The SFM model is derived from the ASM model. To a multicast source, the two models appear to
have the same multicast membership architecture.
The SFM model functionally extends the ASM model. The upper-layer software checks the source
address of received multicast packets and permits or denies multicast traffic from specific sources.
The receivers obtain the multicast data from only part of the multicast sources. To a receiver,
multicast sources are not all valid, but are filtered.
SSM model
The SSM model provides a transmission service that enables multicast receivers to specify the
multicast sources in which they are interested.
In the SSM model, receivers have already determined the locations of the multicast sources. This is
the main difference between the SSM model and the ASM model. In addition, the SSM model uses a
different multicast address range than the ASM/SFM model. Dedicated multicast forwarding paths
are established between receivers and the specified multicast sources.
Multicast architecture
IP multicast addresses the following issues:
•Where should the multicast source transmit information to? (Multicast addressing.)
•What receivers exist on the network? (Host registration.)
•Where is the multicast source that will provide data to the receivers? (Multicast source
discovery.)
•How is the information transmitted to the receivers? (Multicast routing.)
IP multicast is an end-to-end service. The multicast architecture involves the following parts:
•Addressing mechanism—A multicast source sends information to a group of receivers
through a multicast address.
•Host registration—Receiver hosts can join and leave multicast groups dynamically. This
mechanism is the basis for management of group memberships.
•Multicast routing—A multicast distribution tree (a forwarding path tree for multicast data on the
network) is constructed for delivering multicast data from a multicast source to receivers.
•Multicast applications—A software system that supports multicast applications, such as video
conferencing, must be installed on multicast sources and receiver hosts. The TCP/IP stack
must support reception and transmission of multicast data.
Multicast addresses
IP multicast addresses
•IPv4 multicast addresses:
IANA assigned the Class D address block (224.0.0.0 to 239.255.255.255) to IPv4 multicast.

6
Table 2 Class D IP address blocks and description
Address block Description
224.0.0.0 to 224.0.0.255
Reserved permanent group addresses. The IP address
224.0.0.0 is reserved. Other IP addresses can be used by
routing protocols and for topology searching, protocol
maintenance, and so on. Table 3 lists common permanent
group addresses. A packet destined for an address in this
block will not be forwarded beyond the local subnet regardless
of the TTL value in the IP header.
224.0.1.0 to 238.255.255.255
Globally scoped group addresses. This block includes the
following types of designated group addresses:
•232.0.0.0/8—SSM group addresses.
•233.0.0.0/8—Glop group addresses.
239.0.0.0 to 239.255.255.255
Administratively scoped multicast addresses. These
addresses are considered locally unique rather than globally
unique. You can reuse them in domains administered by
different organizations without causing conflicts. For more
information, see RFC 2365.
NOTE:
Glop is a mechanism for assigning multicast addresses between different ASs. By filling an AS
number into the middle two bytes of 233.0.0.0, you get 255 multicast addresses for that AS. Fo
r
more information, see RFC 2770.
Table 3 Common permanent multicast group addresses
Address Description
224.0.0.1 All systems on this subnet, including hosts and routers.
224.0.0.2 All multicast routers on this subnet.
224.0.0.3 Unassigned.
224.0.0.4 DVMRP routers.
224.0.0.5 OSPF routers.
224.0.0.6 OSPF designated routers and backup designated routers.
224.0.0.7 Shared Tree (ST) routers.
224.0.0.8 ST hosts.
224.0.0.9 RIPv2 routers.
224.0.0.11 Mobile agents.
224.0.0.12 DHCP server/relay agent.
224.0.0.13 All Protocol Independent Multicast (PIM) routers.
224.0.0.14 RSVP encapsulation.
224.0.0.15 All Core-Based Tree (CBT) routers.
224.0.0.16 Designated SBM.
224.0.0.17 All SBMs.
224.0.0.18 VRRP.
•IPv6 multicast addresses:

7
Figure 4 IPv6 multicast format
The following describes the fields of an IPv6 multicast address:
{0xFF—The most significant eight bits are 11111111.
{Flags—The Flags field contains four bits.
Figure 5 Flags field format
Table 4 Flags field description
Bit Description
0 Reserved, set to 0.
R
•When set to 0, this address is an IPv6 multicast
address without an embedded RP address.
•When set to 1, this address is an IPv6 multicast
address with an embedded RP address. (The P and T
bits must also be set to 1.)
P
•When set to 0, this address is an IPv6 multicast
address not based on a unicast prefix.
•When set to 1, this address is an IPv6 multicast
address based on a unicast prefix. (The T bit must also
be set to 1.)
T
•When set to 0, this address is an IPv6 multicast
address permanently-assigned by IANA.
•When set to 1, this address is a transient or
dynamically assigned IPv6 multicast address.
{Scope—The Scope field contains four bits, which represent the scope of the IPv6
internetwork for which the multicast traffic is intended.
Table 5 Values of the Scope field
Value Meaning
0, F Reserved.
1 Interface-local scope.
2 Link-local scope.
3 Subnet-local scope.
4 Admin-local scope.
5 Site-local scope.
6, 7, 9 through D Unassigned.
8 Organization-local scope.

8
Value Meaning
E Global scope.
{Group ID—The Group ID field contains 112 bits. It uniquely identifies an IPv6 multicast
group in the scope that the Scope field defines.
Ethernet multicast MAC addresses
•IPv4 multicast MAC addresses:
As defined by IANA, the most significant 24 bits of an IPv4 multicast MAC address are
0x01005E. Bit 25 is 0, and the other 23 bits are the least significant 23 bits of an IPv4 multicast
address.
Figure 6 IPv4-to-MAC address mapping
The most significant four bits of an IPv4 multicast address are fixed at 1110. In an IPv4-to-MAC
address mapping, five bits of the IPv4 multicast address are lost. As a result, 32 IPv4 multicast
addresses are mapped to the same IPv4 multicast MAC address. A device might receive
unwanted multicast data at Layer 2 processing, which needs to be filtered by the upper layer.
•IPv6 multicast MAC addresses:
As defined by IANA, the most significant 16 bits of an IPv6 multicast MAC address are 0x3333.
The least significant 32 bits are mapped from the least significant 32 bits of an IPv6 multicast
address. Therefore, the problem of duplicate IPv6-to-MAC address mapping also arises like
IPv4-to-MAC address mapping.
Figure 7 IPv6-to-MAC address mapping
IMPORTANT:
Because of the duplicate mapping from multicast IP address to multicast MAC address, the device
might inadvertently send multicast protocol packets as multicast data in Layer 2 forwarding. To avoid
this, do not use the IP multicast addresses that are mapped to multicast MAC addresses
0100-5E00-00xx and 3333-0000-00xx (where "x" represents any hexadecimal number from 0 to F).

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Multicast protocols
Multicast protocols include the following categories:
•Layer 3 and Layer 2 multicast protocols:
{Layer 3 multicast refers to IP multicast operating at the network layer.
Layer 3 multicast protocols—IGMP, MLD, PIM, IPv6 PIM, MSDP, MBGP, and IPv6
MBGP.
{Layer 2 multicast refers to IP multicast operating at the data link layer.
Layer 2 multicast protocols—IGMP snooping, MLD snooping, PIM snooping, IPv6 PIM
snooping, multicast VLAN, and IPv6 multicast VLAN.
•IPv4 and IPv6 multicast protocols:
{For IPv4 networks—IGMP snooping, PIM snooping, multicast VLAN, IGMP, PIM, MSDP,
and MBGP.
{For IPv6 networks—MLD snooping, IPv6 PIM snooping, IPv6 multicast VLAN, MLD, IPv6
PIM, and IPv6 MBGP.
This section provides only general descriptions about applications and functions of the Layer 2 and
Layer 3 multicast protocols in a network. For more information about these protocols, see the related
chapters.
Layer 3 multicast protocols
In Figure 8, Layer 3 multicast protocols include multicast group management protocols and multicast
routing protocols.
Figure 8 Positions of Layer 3 multicast protocols
•Multicast group management protocols:
Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) protocol
are multicast group management protocols. Typically, they run between hosts and Layer 3
multicast devices that directly connect to the hosts to establish and maintain multicast group
memberships.
•Multicast routing protocols:
A multicast routing protocol runs on Layer 3 multicast devices to establish and maintain
multicast routes and correctly and efficiently forward multicast packets. Multicast routes
constitute loop-free data transmission paths (also known as multicast distribution trees) from a
data source to multiple receivers.

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In the ASM model, multicast routes include intra-domain routes and inter-domain routes.
{An intra-domain multicast routing protocol discovers multicast sources and builds multicast
distribution trees within an AS to deliver multicast data to receivers. Among a variety of
mature intra-domain multicast routing protocols, PIM is most widely used. Based on the
forwarding mechanism, PIM has dense mode (often referred to as PIM-DM) and sparse
mode (often referred to as PIM-SM).
{An inter-domain multicast routing protocol is used for delivering multicast information
between two ASs. So far, mature solutions include Multicast Source Discovery Protocol
(MSDP) and MBGP. MSDP propagates multicast source information among different ASs.
MBGP is an extension of the MP-BGP for exchanging multicast routing information among
different ASs.
For the SSM model, multicast routes are not divided into intra-domain routes and inter-domain
routes. Because receivers know the positions of the multicast sources, channels established
through PIM-SM are sufficient for the transport of multicast information.
Layer 2 multicast protocols
In Figure 9, Layer 2 multicast protocols include IGMP snooping, MLD snooping, PIM snooping, IPv6
PIM snooping, multicast VLAN, and IPv6 multicast VLAN.
Figure 9 Positions of Layer 2 multicast protocols
•IGMP snooping and MLD snooping:
IGMP snooping and MLD snooping are multicast constraining mechanisms that run on Layer 2
devices. They manage and control multicast groups by monitoring and analyzing IGMP or MLD
messages exchanged between the hosts and Layer 3 multicast devices. This effectively
controls the flooding of multicast data in Layer 2 networks.
•PIM snooping and IPv6 PIM snooping:
PIM snooping and IPv6 PIM snooping run on Layer 2 devices. They work with IGMP snooping
or MLD snooping to analyze received PIM messages. Then, they add the ports that are
interested in specific multicast data to a PIM snooping routing entry or IPv6 PIM snooping
routing entry. In this way, multicast data can be forwarded to only the ports that are interested in
the data.
•Multicast VLAN and IPv6 multicast VLAN:
Multicast VLAN or IPv6 multicast VLAN runs on a Layer 2 device in a multicast network where
multicast receivers for the same group exist in different VLANs. With these protocols, the Layer
3 multicast device sends only one copy of multicast to the multicast VLAN or IPv6 multicast

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VLAN on the Layer 2 device. This method avoids waste of network bandwidth and extra burden
on the Layer 3 device.
Multicast packet forwarding mechanism
In a multicast model, receiver hosts of a multicast group are usually located at different areas on the
network. They are identified by the same multicast group address. To deliver multicast packets to
these receivers, a multicast source encapsulates the multicast data in an IP packet with the multicast
group address as the destination address. Multicast routers on the forwarding paths forward
multicast packets that an incoming interface receives through multiple outgoing interfaces.
Compared to a unicast model, a multicast model is more complex in the following aspects:
•To ensure multicast packet transmission on the network, different routing tables are used to
guide multicast forwarding. These routing tables include unicast routing tables, routing tables
for multicast (for example, the MBGP routing table), and static multicast routing tables.
•To process the same multicast information from different peers received on different interfaces,
the multicast device performs an RPF check on each multicast packet. The RPF check result
determines whether the packet will be forwarded or discarded. The RPF check mechanism is
the basis for most multicast routing protocols to implement multicast forwarding.
For more information about the RPF mechanism, see "Configuring multicast routing and
forwarding" and "Configuring IPv6 multicast routing and forwarding."
Multicast support for VPNs
Multicast support for VPNs refers to multicast applied in VPNs.
Introduction to VPN instances
VPNs are isolated from one another and from the public network. As shown in Figure 10, VPN A and
VPN B separately access the public network through PE devices.

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Figure 10 VPN networking diagram
•The P device belongs to the public network. The CE devices belong to their respective VPNs.
Each CE device serves its own VPN and maintains only one set of forwarding mechanisms.
•The PE devices connect to the public network and the VPNs. Each PE device must strictly
distinguish the information for different networks, and maintain a separate forwarding
mechanism for each network. On a PE device, a set of software and hardware that serve the
same network forms an instance. Multiple instances can exist on the same PE device, and an
instance can reside on different PE devices. On a PE device, the instance for the public network
is called the public network instance, and those for VPNs are called VPN instances.
Multicast application in VPNs
A PE device that supports multicast for VPNs performs the following operations:
•Maintains an independent set of multicast forwarding mechanisms for each VPN, including the
multicast protocols, PIM neighbor information, and multicast routing table. In a VPN, the device
forwards multicast data based on the forwarding table or routing table for that VPN.
•Implements the isolation between different VPNs.
•Implements information exchange and data conversion between the public network and VPN
instances.
For example, as shown in Figure 10, a multicast source in VPN A sends multicast data to a multicast
group. Only receivers that belong to both the multicast group and VPN A can receive the multicast
data. The multicast data is multicast both in VPN A and on the public network.
VPN A
VPN A
VPN A
VPN BVPN B
Public network
P
PE 1
PE 2
PE 3
CE b3
CE a2
CE a3
CE b1
CE a1
CE b2