HP FlexNetwork 7500 Series User manual

HPE FlexNetwork 7500 Switch Series
IP Multicast Configuration Guide
Part number: 5998-7469R
Software version: 7500-CMW710-R7178
Document version: 6W100-20160129

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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 ·····································································································································8
Multicast packet forwarding mechanism ··········································································································11
Configuring IGMP snooping·········································································· 12
Overview ··························································································································································12
IGMP snooping ports ·······························································································································12
How IGMP snooping works······················································································································14
Protocols and standards ··························································································································15
General configuration restrictions and guidelines ····························································································15
IGMP snooping configuration task list··············································································································16
Configuring basic IGMP snooping features ·····································································································16
Enabling IGMP snooping ·························································································································16
Specifying an IGMP snooping version ·····································································································17
Setting the maximum number of IGMP snooping forwarding entries·······················································18
Setting the IGMP last member query interval ··························································································18
Configuring IGMP snooping port features········································································································19
Setting aging timers for dynamic ports·····································································································19
Configuring static ports ····························································································································20
Configuring a port as a simulated member host ······················································································20
Enabling fast-leave processing ················································································································21
Disabling a port from becoming a dynamic router port ············································································21
Configuring the IGMP snooping querier···········································································································22
Configuration prerequisites ······················································································································22
Enabling the IGMP snooping querier ·······································································································22
Configuring parameters for IGMP general queries and responses··························································23
Configuring parameters for IGMP messages···································································································23
Configuration prerequisites ······················································································································24
Configuring source IP addresses for IGMP messages ············································································24
Setting the 802.1p priority for IGMP messages ·······················································································25
Configuring IGMP snooping policies ················································································································25
Configuring a multicast group policy ········································································································25
Enabling multicast source port filtering ····································································································26
Enabling dropping unknown multicast data······························································································27
Enabling IGMP report suppression ··········································································································27
Setting the maximum number of multicast groups on a port····································································28
Enabling multicast group replacement ·····································································································28
Displaying and maintaining IGMP snooping ····································································································29
IGMP snooping configuration examples ··········································································································30
Group policy and simulated joining configuration example ······································································30
Static port configuration example·············································································································32
IGMP snooping querier configuration example ························································································35
Troubleshooting IGMP snooping ·····················································································································37
Layer 2 multicast forwarding cannot function···························································································37
Multicast group policy does not work ·······································································································38
Configuring PIM snooping············································································· 39
Overview ··························································································································································39
Configuring PIM snooping································································································································40

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Displaying and maintaining PIM snooping ·······································································································41
PIM snooping configuration example···············································································································41
Troubleshooting PIM snooping ························································································································45
PIM snooping does not work on a Layer 2 device ···················································································45
Configuring multicast VLANs ········································································ 46
Overview ··························································································································································46
Multicast VLAN configuration task list ··············································································································48
Configuring a sub-VLAN-based multicast VLAN······························································································48
Configuration prerequisites ······················································································································48
Configuration guidelines···························································································································48
Configuration procedure···························································································································48
Configuring a port-based multicast VLAN ········································································································49
Configuration prerequisites ······················································································································49
Configuring user port attributes················································································································49
Assigning user ports to a multicast VLAN ································································································50
Setting the maximum number of multicast VLAN forwarding entries·······························································50
Displaying and maintaining multicast VLANs···································································································51
Multicast VLAN configuration examples ··········································································································51
Sub-VLAN-based multicast VLAN configuration example ·······································································51
Port-based multicast VLAN configuration example··················································································54
Configuring multicast routing and forwarding················································ 58
Overview ··························································································································································58
RPF check mechanism ····························································································································58
Static multicast routes ······························································································································60
Multicast forwarding across unicast subnets····························································································61
Configuration task list·······································································································································62
Enabling IP multicast routing ···························································································································62
Configuring multicast routing and forwarding···································································································62
Configuring static multicast routes ···········································································································62
Specifying the longest prefix match principle ···························································································63
Configuring multicast load splitting···········································································································63
Configuring a multicast forwarding boundary···························································································64
Configuring static multicast MAC address entries····················································································64
Enabling multicast forwarding between sub-VLANs of a super VLAN·····························································65
Displaying and maintaining multicast routing and forwarding ··········································································65
Multicast routing and forwarding configuration examples ················································································67
Changing an RPF route ···························································································································67
Creating an RPF route ·····························································································································69
Multicast forwarding over a GRE tunnel···································································································71
Troubleshooting multicast routing and forwarding ···························································································73
Static multicast route failure ·····················································································································73
Configuring IGMP ························································································· 75
Overview ··························································································································································75
IGMPv1 overview ·····································································································································75
IGMPv2 enhancements····························································································································76
IGMPv3 enhancements····························································································································77
IGMP SSM mapping ································································································································78
IGMP support for VPNs····························································································································79
Protocols and standards ··························································································································79
IGMP configuration task list ·····························································································································80
Configuring basic IGMP features ·····················································································································80
Enabling IGMP ·········································································································································80
Specifying an IGMP version·····················································································································81
Configuring a static group member ··········································································································81
Configuring a multicast group policy ········································································································81
Adjusting IGMP performance···························································································································82
Configuring IGMP query and response parameters·················································································82
Enabling fast-leave processing ················································································································84
Enabling IGMP NSR ········································································································································85

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Configuring IGMP SSM mappings ···················································································································85
Configuration prerequisites ······················································································································85
Configuration procedure···························································································································85
Displaying and maintaining IGMP····················································································································85
IGMP configuration examples··························································································································86
Basic IGMP features configuration examples ··························································································86
IGMP SSM mapping configuration example ····························································································88
Troubleshooting IGMP ·····································································································································91
No membership information on the receiver-side router ··········································································91
Inconsistent membership information on the routers on the same subnet···············································92
Configuring PIM ···························································································· 94
Overview ··························································································································································94
PIM-DM overview·····································································································································94
PIM-SM overview ·····································································································································96
BIDIR-PIM overview·······························································································································100
Administrative scoping overview ············································································································103
PIM-SSM overview·································································································································105
Relationship among PIM protocols ········································································································106
PIM support for VPNs ····························································································································107
Protocols and standards ························································································································107
Configuring PIM-DM ······································································································································107
PIM-DM configuration task list ···············································································································108
Configuration prerequisites ····················································································································108
Enabling PIM-DM ···································································································································108
Enabling the state refresh feature ··········································································································108
Configuring state refresh parameters·····································································································109
Configuring PIM-DM graft retry timer ·····································································································109
Configuring PIM-SM·······································································································································110
PIM-SM configuration task list················································································································110
Configuration prerequisites ····················································································································110
Enabling PIM-SM ···································································································································110
Configuring an RP··································································································································111
Configuring a BSR ·································································································································112
Configuring multicast source registration ·······························································································114
Configuring the switchover to SPT·········································································································115
Configuring BIDIR-PIM ··································································································································115
Configuration restrictions and guidelines ·······························································································115
BIDIR-PIM configuration task list ···········································································································115
Configuration prerequisites ····················································································································116
Enabling BIDIR-PIM ·······························································································································116
Configuring an RP··································································································································117
Configuring a BSR ·································································································································118
Configuring PIM-SSM ····································································································································120
PIM-SSM configuration task list ·············································································································120
Configuration prerequisites ····················································································································120
Enabling PIM-SM ···································································································································121
Configuring the SSM group range··········································································································121
Configuring common PIM features ················································································································122
Configuration task list·····························································································································122
Configuration prerequisites ····················································································································122
Configuring a multicast source policy·····································································································122
Configuring a PIM hello policy················································································································122
Configuring PIM hello message options·································································································123
Configuring common PIM timers············································································································124
Setting the maximum size of each join or prune message·····································································126
Enabling BFD for PIM ····························································································································126
Enabling PIM passive mode···················································································································126
Enabling PIM NSR ·································································································································127
Displaying and maintaining PIM·····················································································································127
PIM configuration examples···························································································································128
PIM-DM configuration example··············································································································128

iv
PIM-SM non-scoped zone configuration example ·················································································131
PIM-SM admin-scoped zone configuration example··············································································134
BIDIR-PIM configuration example··········································································································139
PIM-SSM configuration example············································································································143
Troubleshooting PIM······································································································································146
A multicast distribution tree cannot be correctly built ·············································································146
Multicast data is abnormally terminated on an intermediate router························································147
An RP cannot join an SPT in PIM-SM····································································································147
An RPT cannot be built or multicast source registration fails in PIM-SM ···············································147
Configuring MSDP ······················································································ 149
Overview ························································································································································149
How MSDP works ··································································································································149
MSDP support for VPNs ························································································································154
Protocols and standards ························································································································154
MSDP configuration task list ··························································································································155
Configuring basic MSDP features··················································································································155
Configuration prerequisites ····················································································································155
Enabling MSDP······································································································································155
Specifying an MSDP peer ······················································································································156
Configuring a static RPF peer ················································································································156
Configuring an MSDP peering connection·····································································································156
Configuration prerequisites ····················································································································157
Configuring a description for an MSDP peer··························································································157
Configuring an MSDP mesh group ········································································································157
Controlling MSDP peering connections ·································································································157
Configuring SA message-related parameters································································································158
Configuration prerequisites ····················································································································158
Enabling multicast data encapsulation in SA messages········································································159
Configuring the originating RP of SA messages ····················································································159
Configuring SA request messages·········································································································159
Configuring SA message policies ··········································································································160
Configuring the SA cache mechanism ···································································································161
Displaying and maintaining MSDP·················································································································161
MSDP configuration examples·······················································································································162
PIM-SM inter-domain multicast configuration ························································································162
Inter-AS multicast configuration by leveraging static RPF peers ···························································167
Anycast RP configuration·······················································································································171
SA message filtering configuration·········································································································175
Troubleshooting MSDP··································································································································178
MSDP peers stay in disabled state ········································································································178
No SA entries exist in the router's SA message cache··········································································178
No exchange of locally registered (S, G) entries between RPs ·····························································178
Configuring multicast VPN ·········································································· 180
Overview ························································································································································180
MD VPN overview ··································································································································181
Protocols and standards ························································································································184
How MD VPN works·······································································································································185
Default-MDT establishment····················································································································185
Default-MDT-based delivery ··················································································································187
MDT switchover ·····································································································································190
Inter-AS MD VPN ···································································································································191
Multicast VPN configuration task list ··············································································································193
Configuring MD VPN······································································································································194
Configuration prerequisites ····················································································································194
Enabling IP multicast routing in a VPN instance ····················································································194
Creating an MD for a VPN instance ·······································································································195
Specifying the default-group ··················································································································195
Specifying the MD source interface ·······································································································195
Configuring MDT switchover parameters·······························································································196
Enabling data-group reuse logging ········································································································196

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Configuring BGP MDT ···································································································································196
Configuration prerequisites ····················································································································197
Enabling BGP MDT peers or peer groups ·····························································································197
Configuring a BGP MDT route reflector ·································································································197
Displaying and maintaining multicast VPN ····································································································198
Multicast VPN configuration examples ··········································································································199
Intra-AS MD VPN configuration example·······························································································199
MD VPN inter-AS option C configuration example·················································································212
Troubleshooting MD VPN ······························································································································225
A default-MDT cannot be established ····································································································225
An MVRF cannot be created··················································································································226
Configuring MLD snooping ········································································· 227
Overview ························································································································································227
MLD snooping ports ·······························································································································227
How MLD snooping works ·····················································································································229
Protocols and standards ························································································································230
General configuration restrictions and guidelines ··························································································230
MLD snooping configuration task list ·············································································································231
Configuring basic MLD snooping features ·····································································································231
Enabling MLD snooping ·························································································································231
Specifying an MLD snooping version·····································································································232
Setting the maximum number of MLD snooping forwarding entries ······················································233
Setting the MLD last listener query interval····························································································233
Configuring MLD snooping port features ·······································································································234
Setting aging timers for dynamic ports···································································································234
Configuring static ports ··························································································································235
Configuring a port as a simulated member host ····················································································235
Enabling fast-leave processing ··············································································································236
Disabling a port from becoming a dynamic router port ··········································································237
Configuring the MLD snooping querier ··········································································································237
Configuration prerequisites ····················································································································237
Enabling the MLD snooping querier·······································································································237
Configuring parameters for MLD general queries and responses ·························································238
Configuring parameters for MLD messages ··································································································239
Configuration prerequisites ····················································································································239
Configuring source IPv6 addresses for MLD messages ········································································239
Setting the 802.1p priority for MLD messages ·······················································································240
Configuring MLD snooping policies ···············································································································241
Configuring an IPv6 multicast group policy ····························································································241
Enabling IPv6 multicast source port filtering ··························································································242
Enabling dropping unknown IPv6 multicast data ···················································································242
Enabling MLD report suppression··········································································································243
Setting the maximum number of IPv6 multicast groups on a port··························································243
Enabling IPv6 multicast group replacement···························································································244
Displaying and maintaining MLD snooping ····································································································244
MLD snooping configuration examples··········································································································246
IPv6 group policy and simulated joining configuration example·····························································246
Static port configuration example···········································································································248
MLD snooping querier configuration example························································································251
Troubleshooting MLD snooping ·····················································································································253
Layer 2 multicast forwarding cannot function·························································································253
IPv6 multicast group policy does not work ·····························································································253
Configuring IPv6 PIM snooping ·································································· 255
Overview ························································································································································255
Configuring IPv6 PIM snooping ·····················································································································256
Displaying and maintaining IPv6 PIM snooping·····························································································257
IPv6 PIM snooping configuration example·····································································································257
Troubleshooting IPv6 PIM snooping ··············································································································261
IPv6 PIM snooping does not work on a Layer 2 device ·········································································261

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Configuring IPv6 multicast VLANs ······························································ 262
Overview ························································································································································262
IPv6 multicast VLAN configuration task list····································································································264
Configuring a sub-VLAN-based IPv6 multicast VLAN ···················································································264
Configuration prerequisites ····················································································································264
Configuration guidelines·························································································································264
Configuration procedure·························································································································264
Configuring a port-based IPv6 multicast VLAN······························································································265
Configuration prerequisites ····················································································································265
Configuring user port attributes··············································································································265
Assigning user ports to an IPv6 multicast VLAN····················································································266
Setting the maximum number of IPv6 multicast VLAN forwarding entries·····················································266
Displaying and maintaining IPv6 multicast VLANs ························································································267
IPv6 multicast VLAN configuration examples ································································································267
Sub-VLAN-based IPv6 multicast VLAN configuration example ·····························································267
Port-based IPv6 multicast VLAN configuration example········································································270
Configuring IPv6 multicast routing and forwarding······································ 274
Overview ························································································································································274
RPF check mechanism ··························································································································274
IPv6 multicast forwarding across IPv6 unicast subnets ·········································································276
Configuration task list·····································································································································276
Enabling IPv6 multicast routing······················································································································276
Configuring IPv6 multicast routing and forwarding ························································································277
Specifying the longest prefix match principle ·························································································277
Configuring IPv6 multicast load splitting ································································································277
Configuring an IPv6 multicast forwarding boundary···············································································278
Configuring IPv6 static multicast MAC address entries ·········································································278
Enabling IPv6 multicast forwarding between sub-VLANs of a super VLAN···········································279
Displaying and maintaining IPv6 multicast routing and forwarding ································································279
IPv6 multicast forwarding over a GRE tunnel configuration example ····························································281
Network requirements ····························································································································281
Configuration procedure·························································································································281
Verifying the configuration······················································································································283
Configuring MLD ························································································· 284
Overview ························································································································································284
How MLDv1 works ·································································································································284
MLDv2 enhancements ···························································································································286
MLD SSM mapping ································································································································287
MLD support for VPNs ···························································································································288
Protocols and standards ························································································································288
MLD configuration task list·····························································································································288
Configuring basic MLD features·····················································································································288
Enabling MLD·········································································································································288
Specifying an MLD version ····················································································································289
Configuring a static group member ········································································································289
Configuring an IPv6 multicast group policy ····························································································290
Adjusting MLD performance ··························································································································290
Configuring MLD query and response parameters ················································································290
Enabling fast-leave processing ··············································································································292
Enabling MLD NSR ········································································································································292
Configuring MLD SSM mappings···················································································································293
Configuration prerequisites ····················································································································293
Configuration procedure·························································································································293
Displaying and maintaining MLD ···················································································································293
MLD configuration examples ·························································································································294
Basic MLD features configuration example····························································································294
MLD SSM mapping configuration example····························································································296
Troubleshooting MLD·····································································································································299
No member information exists on the receiver-side router ····································································299

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Inconsistent membership information on the routers on the same subnet·············································300
Configuring IPv6 PIM ·················································································· 301
Overview ························································································································································301
IPv6 PIM-DM overview···························································································································301
IPv6 PIM-SM overview···························································································································303
IPv6 BIDIR-PIM overview·······················································································································308
IPv6 administrative scoping overview ····································································································311
IPv6 PIM-SSM overview ························································································································313
Relationship among IPv6 PIM protocols ································································································314
IPv6 PIM support for VPNs ····················································································································315
Protocols and standards ························································································································315
Configuring IPv6 PIM-DM ······························································································································315
IPv6 PIM-DM configuration task list ·······································································································316
Configuration prerequisites ····················································································································316
Enabling IPv6 PIM-DM···························································································································316
Enabling the state refresh feature ··········································································································316
Configuring state refresh parameters·····································································································317
Configuring IPv6 PIM-DM graft retry timer ·····························································································317
Configuring IPv6 PIM-SM ······························································································································318
IPv6 PIM-SM configuration task list ·······································································································318
Configuration prerequisites ····················································································································318
Enabling IPv6 PIM-SM ···························································································································318
Configuring an RP··································································································································319
Configuring a BSR ·································································································································320
Configuring IPv6 multicast source registration·······················································································322
Configuring the switchover to SPT·········································································································322
Configuring IPv6 BIDIR-PIM ··························································································································323
Configuration restrictions and guidelines ·······························································································323
IPv6 BIDIR-PIM configuration task list ···································································································323
Configuration prerequisites ····················································································································323
Enabling IPv6 BIDIR-PIM·······················································································································323
Configuring an RP··································································································································324
Configuring a BSR ·································································································································326
Configuring IPv6 PIM-SSM ····························································································································327
IPv6 PIM-SSM configuration task list ·····································································································328
Configuration prerequisites ····················································································································328
Enabling IPv6 PIM-SM ···························································································································328
Configuring the IPv6 SSM group range ·································································································328
Configuring common IPv6 PIM features ········································································································329
Configuration task list·····························································································································329
Configuration prerequisites ····················································································································329
Configuring an IPv6 multicast source policy ··························································································329
Configuring an IPv6 PIM hello policy ·····································································································330
Configuring IPv6 PIM hello message options ························································································330
Configuring common IPv6 PIM timers····································································································332
Setting the maximum size of each join or prune message·····································································333
Enabling BFD for IPv6 PIM ····················································································································333
Enabling IPv6 PIM passive mode ··········································································································334
Enabling IPv6 PIM NSR ·························································································································334
Displaying and maintaining IPv6 PIM ············································································································335
IPv6 PIM configuration examples ··················································································································335
IPv6 PIM-DM configuration example······································································································335
IPv6 PIM-SM non-scoped zone configuration example ·········································································338
IPv6 PIM-SM admin-scoped zone configuration example ·····································································341
IPv6 BIDIR-PIM configuration example··································································································347
IPv6 PIM-SSM configuration example ···································································································351
Troubleshooting IPv6 PIM······························································································································354
A multicast distribution tree cannot be correctly built ·············································································354
IPv6 multicast data is abnormally terminated on an intermediate router ···············································354
An RP cannot join an SPT in IPv6 PIM-SM ···························································································355
An RPT cannot be built or IPv6 multicast source registration fails in IPv6 PIM-SM·······························355

viii
Document conventions and icons ······························································· 356
Conventions ···················································································································································356
Network topology icons··································································································································357
Support and other resources ······································································ 358
Accessing Hewlett Packard Enterprise Support ····························································································358
Accessing updates·········································································································································358
Websites ················································································································································359
Customer self repair·······························································································································359
Remote support······································································································································359
Documentation feedback ·······················································································································359
Index ··········································································································· 361

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
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
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.

9
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
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.
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).

10
{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
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
VLAN on the Layer 2 device. This method avoids waste of network bandwidth and extra burden
on the Layer 3 device.