HP FlexFabric 5950 Series User manual

HPE FlexFabric 5950 Switch Series
IP Multicast Configuration Guide
P
art number: 5200-2212a
Software
version: Release 6123 and later
Document version: 6W101-20170120

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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
IP multicast architecture ··············································································································5
Multicast addresses·············································································································5
Multicast protocols···············································································································8
Multicast packet forwarding mechanism························································································10
Multicast support for VPNs········································································································· 11
Introduction to VPN instances ······························································································11
Multicast application in VPNs·······························································································12
Configuring IGMP snooping······························································13
Overview································································································································ 13
IGMP snooping ports ·········································································································13
How IGMP snooping works ·································································································15
IGMP snooping proxying·····································································································16
Protocols and standards ·····································································································17
IGMP snooping configuration task list···························································································17
IGMP snooping configuration task list for VLANs······································································17
IGMP configuration task list for VSIs······················································································18
Configuring basic IGMP snooping features····················································································19
Enabling IGMP snooping ····································································································19
Specifying an IGMP snooping version····················································································19
Setting the maximum number of IGMP snooping forwarding entries ·············································20
Configuring static multicast MAC address entries·····································································21
Setting the IGMP last member query interval···········································································21
Configuring IGMP snooping port features······················································································22
Setting aging timers for dynamic ports ···················································································22
Configuring static ports·······································································································23
Configuring a port as a simulated member host ·······································································24
Enabling fast-leave processing·····························································································24
Disabling a port from becoming a dynamic router port·······························································25
Configuring the IGMP snooping querier ························································································25
Configuration prerequisites··································································································25
Enabling the IGMP snooping querier ·····················································································26
Configuring parameters for IGMP general queries and responses················································26
Enabling IGMP snooping proxying·······························································································27
Configuring parameters for IGMP messages··················································································27
Configuration prerequisites··································································································27
Configuring source IP addresses for IGMP messages·······························································28
Setting the 802.1p priority for IGMP messages ········································································29
Configuring IGMP snooping policies·····························································································30
Configuring a multicast group policy ······················································································30
Enabling multicast source port filtering···················································································31
Enabling dropping unknown multicast data ·············································································31
Enabling IGMP report suppression························································································32
Setting the maximum number of multicast groups on a port························································32
Enabling multicast group replacement····················································································33
Enabling host tracking········································································································33
Displaying and maintaining IGMP snooping···················································································34
IGMP snooping configuration examples························································································35
Group policy and simulated joining configuration example(for VLANs) ··········································35
Static port configuration example (for VLANs)··········································································37

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IGMP snooping querier configuration example (for VLANs) ························································39
IGMP snooping proxying configuration example (for VLANs) ······················································42
IGMP snooping configuration example (for VSIs) ·····································································43
IGMP snooping configuration example (for VXLANs) ································································49
Troubleshooting IGMP snooping ·································································································54
Layer 2 multicast forwarding cannot function···········································································54
Multicast group policy does not work ·····················································································55
Configuring PIM snooping································································56
Overview································································································································ 56
Configuring PIM snooping··········································································································57
Displaying and maintaining PIM snooping ·····················································································58
PIM snooping configuration example (for VLANs) ···········································································58
Network requirements ········································································································58
Configuration procedure ·····································································································59
Verifying the configuration···································································································61
Troubleshooting PIM snooping···································································································· 62
PIM snooping does not work on a Layer 2 device·····································································62
Configuring multicast VLANs ····························································63
Overview································································································································ 63
Multicast VLAN configuration task list···························································································65
Configuring a sub-VLAN-based multicast VLAN ············································································· 65
Configuration prerequisites··································································································65
Configuration restrictions and guidelines ················································································65
Configuration procedure ····································································································· 66
Configuring a port-based multicast VLAN······················································································66
Configuration prerequisites··································································································66
Configuring user port attributes ···························································································· 66
Assigning user ports to a multicast VLAN ···············································································67
Setting the maximum number of multicast VLAN forwarding entries····················································67
Displaying and maintaining multicast VLANs··················································································68
Multicast VLAN configuration examples························································································68
Sub-VLAN-based multicast VLAN configuration example···························································68
Port-based multicast VLAN configuration example····································································71
Configuring multicast routing and forwarding········································75
Overview································································································································ 75
RPF check mechanism·······································································································75
Static multicast routes ········································································································77
Multicast forwarding across unicast subnets············································································78
Configuration task list················································································································79
Enabling IP multicast routing ······································································································79
Configuring multicast routing and forwarding··················································································80
Configuring static multicast routes·························································································80
Specifying the longest prefix match principle ···········································································80
Configuring multicast load splitting ························································································81
Configuring a multicast forwarding boundary···········································································81
Enabling multicast forwarding between sub-VLANs of a super VLAN ··················································81
Displaying and maintaining multicast routing and forwarding ·····························································82
Configuration examples·············································································································83
Changing an RPF route······································································································83
Creating an RPF route········································································································85
Multicast forwarding over a GRE tunnel··················································································87
Troubleshooting multicast routing and forwarding············································································90
Static multicast route failure·································································································90
Configuring IGMP···········································································91
Overview································································································································ 91
IGMPv1 overview··············································································································91
IGMPv2 enhancements ······································································································ 92
IGMPv3 enhancements ······································································································ 93

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IGMP SSM mapping ··········································································································94
IGMP proxying·················································································································· 95
IGMP support for VPNs ······································································································96
Protocols and standards ·····································································································96
IGMP configuration task list········································································································ 97
Configuring basic IGMP features·································································································97
Enabling IGMP ················································································································· 97
Specifying an IGMP version································································································· 98
Configuring a static group member························································································98
Configuring a multicast group policy ······················································································98
Adjusting IGMP performance······································································································99
Configuring IGMP query and response parameters···································································99
Enabling fast-leave processing··························································································· 101
Configuring IGMP SSM mappings ····························································································· 102
Configuration prerequisites································································································ 102
Configuration procedure ··································································································· 102
Configuring IGMP proxying ······································································································ 102
Configuration prerequisites································································································ 102
Enabling IGMP proxying ··································································································· 102
Enabling multicast forwarding on a non-querier interface ························································· 103
Configuring multicast load splitting on an IGMP proxy ····························································· 103
Enabling IGMP NSR··············································································································· 104
Displaying and maintaining IGMP······························································································ 104
IGMP configuration examples··································································································· 105
Basic IGMP features configuration example·········································································· 105
IGMP SSM mapping configuration example ·········································································· 107
IGMP proxying configuration example·················································································· 110
Troubleshooting IGMP ············································································································ 111
No membership information on the receiver-side router··························································· 111
Inconsistent membership information on the routers on the same subnet ···································· 111
Configuring PIM··········································································· 113
Overview······························································································································ 113
PIM-DM overview············································································································ 113
PIM-SM overview············································································································ 115
BIDIR-PIM overview········································································································· 121
Administrative scoping overview························································································· 124
PIM-SSM overview·········································································································· 126
Relationship among PIM protocols······················································································ 127
PIM support for VPNs······································································································· 128
Protocols and standards ··································································································· 128
Configuring PIM-DM··············································································································· 128
PIM-DM configuration task list···························································································· 129
Configuration prerequisites································································································ 129
Enabling PIM-DM············································································································ 129
Enabling the state refresh feature ······················································································· 129
Configuring state refresh parameters··················································································· 130
Configuring the PIM-DM graft retry timer ·············································································· 130
Configuring PIM-SM ··············································································································· 131
PIM-SM configuration task list···························································································· 131
Configuration prerequisites································································································ 131
Enabling PIM-SM ············································································································ 131
Configuring an RP··········································································································· 132
Configuring a BSR··········································································································· 134
Configuring multicast source registration ·············································································· 136
Configuring the switchover to SPT ······················································································ 137
Configuring BIDIR-PIM············································································································ 137
BIDIR-PIM configuration task list ························································································ 137
Configuration prerequisites································································································ 138
Enabling BIDIR-PIM········································································································· 138
Configuring an RP··········································································································· 138
Configuring a BSR··········································································································· 140

iv
Configuring PIM-SSM ············································································································· 143
PIM-SSM configuration task list·························································································· 143
Configuration prerequisites································································································ 143
Enabling PIM-SM ············································································································ 143
Configuring the SSM group range······················································································· 143
Configuring common PIM features····························································································· 144
Configuration task list······································································································· 144
Configuration prerequisites································································································ 144
Configuring a multicast source policy··················································································· 145
Configuring a PIM hello policy···························································································· 145
Configuring PIM hello message options················································································ 145
Configuring common PIM timers························································································· 147
Setting the maximum size of a join or prune message····························································· 148
Enabling BFD for PIM······································································································· 148
Enabling PIM passive mode ······························································································ 149
Enabling PIM NSR··········································································································· 149
Enabling SNMP notifications for PIM ··················································································· 149
Setting a DSCP value for outgoing PIM messages ································································· 150
Displaying and maintaining PIM ································································································ 150
PIM configuration examples ····································································································· 151
PIM-DM configuration example ·························································································· 151
PIM-SM non-scoped zone configuration example··································································· 154
PIM-SM admin-scoped zone configuration example································································ 156
BIDIR-PIM configuration example ······················································································· 161
PIM-SSM configuration example························································································· 165
Troubleshooting PIM··············································································································· 168
A multicast distribution tree cannot be correctly built ······························································· 168
Multicast data is abnormally terminated on an intermediate router ············································· 169
An RP cannot join an SPT in PIM-SM·················································································· 169
An RPT cannot be built or multicast source registration fails in PIM-SM ······································ 169
Configuring MSDP········································································ 171
Overview······························································································································ 171
How MSDP works ··········································································································· 171
MSDP support for VPNs ··································································································· 176
Protocols and standards ··································································································· 176
MSDP configuration task list····································································································· 177
Configuring basic MSDP features······························································································ 177
Configuration prerequisites································································································ 177
Enabling MSDP ·············································································································· 177
Specifying an MSDP peer ································································································· 178
Configuring a static RPF peer ···························································································· 178
Configuring an MSDP peering connection··················································································· 178
Configuration prerequisites································································································ 178
Configuring a description for an MSDP peer·········································································· 178
Configuring an MSDP mesh group······················································································ 179
Controlling MSDP peering connections ················································································ 179
Configuring SA message-related parameters··············································································· 180
Configuration prerequisites································································································ 180
Enabling multicast data encapsulation in SA messages··························································· 180
Configuring the originating RP of SA messages····································································· 181
Configuring SA request messages ······················································································ 181
Configuring SA message policies························································································ 182
Configuring the SA cache mechanism ················································································· 183
Enabling MSDP NSR·············································································································· 183
Displaying and maintaining MSDP····························································································· 183
MSDP configuration examples·································································································· 184
PIM-SM inter-domain multicast configuration········································································· 184
Inter-AS multicast configuration by leveraging static RPF peers ················································ 189
Anycast RP configuration·································································································· 193
SA message filtering configuration ······················································································ 197
Troubleshooting MSDP ··········································································································· 200

v
MSDP peers stay in disabled state······················································································ 201
No SA entries exist in the router's SA message cache····························································· 201
No exchange of locally registered (S, G) entries between RPs ·················································· 202
Configuring multicast VPN ····························································· 203
Overview······························································································································ 203
MD VPN overview ··········································································································· 204
Protocols and standards ··································································································· 207
How MD VPN works··············································································································· 207
Default-MDT establishment ······························································································· 208
Default-MDT-based delivery ······························································································ 211
MDT switchover·············································································································· 214
Inter-AS MD VPN ············································································································ 215
M6VPE ························································································································· 218
Multicast VPN configuration task list··························································································· 219
Configuring MD VPN ·············································································································· 220
Configuration prerequisites································································································ 220
Enabling IP multicast routing for a VPN instance···································································· 220
Creating an MD for a VPN instance····················································································· 221
Create an MD address family····························································································· 221
Specifying the default-group ······························································································ 221
Specifying the MD source interface ····················································································· 222
Configuring MDT switchover parameters·············································································· 222
Configuring the RPF vector feature ····················································································· 223
Enabling data-group reuse logging······················································································ 224
Configuring BGP MDT ············································································································ 224
Configuration prerequisites································································································ 224
Configuring BGP MDT peers or peer groups ········································································· 225
Configuring a BGP MDT route reflector················································································ 225
Displaying and maintaining multicast VPN··················································································· 226
Multicast VPN configuration examples························································································ 227
Intra-AS MD VPN configuration example·············································································· 227
Intra-AS M6VPE configuration example················································································ 240
MD VPN inter-AS option B configuration example ·································································· 255
MD VPN inter-AS option C configuration example ·································································· 269
Troubleshooting MD VPN ········································································································ 283
A default-MDT cannot be established ·················································································· 283
An MVRF cannot be created······························································································ 283
Configuring MLD snooping····························································· 285
Overview······························································································································ 285
MLD snooping ports········································································································· 285
How MLD snooping works································································································· 287
MLD snooping proxying ···································································································· 288
Protocols and standards ··································································································· 289
MLD snooping configuration task list·························································································· 289
MLD snooping configuration task list for VLANs····································································· 289
MLD snooping configuration task list for VSIs········································································ 290
Configuring basic MLD snooping features ··················································································· 291
Enabling MLD snooping···································································································· 291
Specifying an MLD snooping version··················································································· 291
Setting the maximum number of MLD snooping forwarding entries············································· 292
Configuring static IPv6 multicast MAC address entries ···························································· 293
Setting the MLD last listener query interval ··········································································· 293
Configuring MLD snooping port features····················································································· 294
Setting aging timers for dynamic ports ················································································· 294
Configuring static ports····································································································· 295
Configuring a port as a simulated member host ····································································· 296
Enabling fast-leave processing··························································································· 296
Disabling a port from becoming a dynamic router port····························································· 297
Configuring the MLD snooping querier························································································ 297
Configuration prerequisites································································································ 297

vi
Enabling the MLD snooping querier····················································································· 298
Configuring parameters for MLD general queries and responses··············································· 298
Enabling MLD snooping proxying ······························································································ 299
Configuring parameters for MLD messages················································································· 299
Configuration prerequisites································································································ 299
Configuring source IPv6 addresses for MLD messages··························································· 300
Setting the 802.1p priority for MLD messages········································································ 302
Configuring MLD snooping policies···························································································· 302
Configuring an IPv6 multicast group policy············································································ 302
Enabling IPv6 multicast source port filtering ·········································································· 303
Enabling dropping unknown IPv6 multicast data····································································· 304
Enabling MLD report suppression ······················································································· 304
Setting the maximum number of IPv6 multicast groups on a port ··············································· 304
Enabling IPv6 multicast group replacement··········································································· 305
Enabling host tracking······································································································ 305
Displaying and maintaining MLD snooping ·················································································· 306
MLD snooping configuration examples ······················································································· 307
IPv6 group policy and simulated joining configuration example (for VLANs) ································· 307
Static port configuration example (for VLANs)········································································ 309
MLD snooping querier configuration example (for VLANs)························································ 312
MLD snooping proxying configuration example (for VLANs)······················································ 314
MLD snooping configuration example (for VSIs)····································································· 316
MLD snooping configuration example (for VXLANs)································································ 322
Troubleshooting MLD snooping································································································· 326
Layer 2 multicast forwarding cannot function········································································· 326
IPv6 multicast group policy does not work············································································· 327
Configuring IPv6 PIM snooping······················································· 328
Overview······························································································································ 328
Configuring IPv6 PIM snooping································································································· 329
Displaying and maintaining IPv6 PIM snooping ············································································ 330
IPv6 PIM snooping configuration example (for VLANs) ·································································· 330
Network requirements ······································································································ 330
Configuration procedure ··································································································· 331
Verifying the configuration································································································· 333
Troubleshooting IPv6 PIM snooping··························································································· 334
IPv6 PIM snooping does not work on a Layer 2 device···························································· 334
Configuring IPv6 multicast VLANs···················································· 335
Overview······························································································································ 335
IPv6 multicast VLAN configuration task list·················································································· 337
Configuring a sub-VLAN-based IPv6 multicast VLAN····································································· 337
Configuration prerequisites································································································ 337
Configuration restrictions and guidelines ·············································································· 337
Configuration procedure ··································································································· 337
Configuring a port-based IPv6 multicast VLAN ············································································· 338
Configuration prerequisites································································································ 338
Configuring user port attributes ·························································································· 338
Assigning user ports to an IPv6 multicast VLAN····································································· 338
Setting the maximum number of IPv6 multicast VLAN forwarding entries··········································· 339
Displaying and maintaining IPv6 multicast VLANs········································································· 340
IPv6 multicast VLAN configuration examples ··············································································· 340
Sub-VLAN-based IPv6 multicast VLAN configuration example ·················································· 340
Port-based IPv6 multicast VLAN configuration example··························································· 343
Configuring IPv6 multicast routing and forwarding······························· 347
Overview······························································································································ 347
RPF check mechanism····································································································· 347
IPv6 multicast forwarding across IPv6 unicast subnets···························································· 349
Configuration task list·············································································································· 349
Enabling IPv6 multicast routing································································································· 349
Configuring IPv6 multicast routing and forwarding········································································· 350

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Specifying the longest prefix match principle ········································································· 350
Configuring IPv6 multicast load splitting ··············································································· 350
Configuring an IPv6 multicast forwarding boundary································································· 350
Enabling IPv6 multicast forwarding between sub-VLANs of a super VLAN··································· 351
Displaying and maintaining IPv6 multicast routing and forwarding ···················································· 351
IPv6 multicast routing and forwarding configuration examples ························································· 353
IPv6 multicast forwarding over a GRE tunnel········································································· 353
Configuring MLD·········································································· 356
Overview······························································································································ 356
How MLDv1 works··········································································································· 356
MLDv2 enhancements······································································································ 358
MLD SSM mapping·········································································································· 359
MLD proxying················································································································· 360
MLD support for VPNs······································································································ 360
Protocols and standards ··································································································· 360
MLD configuration task list······································································································· 361
Configuring basic MLD features ································································································ 361
Enabling MLD················································································································· 361
Specifying an MLD version································································································ 362
Configuring a static group member······················································································ 362
Configuring an IPv6 multicast group policy············································································ 362
Adjusting MLD performance····································································································· 363
Configuring MLD query and response parameters·································································· 363
Enabling fast-leave processing··························································································· 365
Configuring MLD SSM mappings······························································································· 365
Configuration prerequisites································································································ 366
Configuration procedure ··································································································· 366
Configuring MLD proxying········································································································ 366
Configuration prerequisites································································································ 366
Enabling MLD proxying····································································································· 366
Enabling IPv6 multicast forwarding on a non-querier interface··················································· 367
Configuring IPv6 multicast load splitting on an MLD proxy························································ 367
Enabling MLD NSR ················································································································ 367
Displaying and maintaining MLD ······························································································· 368
MLD configuration examples ···································································································· 368
Basic MLD features configuration examples·········································································· 368
MLD SSM mapping configuration example············································································ 371
MLD proxying configuration example··················································································· 373
Troubleshooting MLD·············································································································· 375
No member information exists on the receiver-side router························································ 375
Inconsistent membership information on the routers on the same subnet ···································· 375
Configuring IPv6 PIM···································································· 376
Overview······························································································································ 376
IPv6 PIM-DM overview ····································································································· 376
IPv6 PIM-SM overview ····································································································· 378
IPv6 BIDIR-PIM overview·································································································· 384
IPv6 administrative scoping overview··················································································· 387
IPv6 PIM-SSM overview ··································································································· 389
Relationship among IPv6 PIM protocols ··············································································· 390
IPv6 PIM support for VPNs································································································ 391
Protocols and standards ··································································································· 391
Configuring IPv6 PIM-DM ········································································································ 391
IPv6 PIM-DM configuration task list····················································································· 392
Configuration prerequisites································································································ 392
Enabling IPv6 PIM-DM ····································································································· 392
Enabling the state refresh feature ······················································································· 392
Configuring state refresh parameters··················································································· 393
Configuring the IPv6 PIM-DM graft retry timer········································································ 393
Configuring IPv6 PIM-SM ········································································································ 394
IPv6 PIM-SM configuration task list ····················································································· 394

viii
Configuration prerequisites································································································ 394
Enabling IPv6 PIM-SM ····································································································· 394
Configuring an RP··········································································································· 395
Configuring a BSR··········································································································· 397
Configuring IPv6 multicast source registration ······································································· 399
Configuring the switchover to SPT ······················································································ 400
Configuring IPv6 BIDIR-PIM····································································································· 400
IPv6 BIDIR-PIM configuration task list·················································································· 400
Configuration prerequisites································································································ 401
Enabling IPv6 BIDIR-PIM·································································································· 401
Configuring an RP··········································································································· 401
Configuring a BSR··········································································································· 403
Configuring IPv6 PIM-SSM ······································································································ 405
IPv6 PIM-SSM configuration task list ··················································································· 405
Configuration prerequisites································································································ 406
Enabling IPv6 PIM-SM ····································································································· 406
Configuring the IPv6 SSM group range ················································································ 406
Configuring common IPv6 PIM features······················································································ 407
Configuration task list······································································································· 407
Configuration prerequisites································································································ 407
Configuring an IPv6 multicast source policy ·········································································· 407
Configuring an IPv6 PIM hello policy···················································································· 408
Configuring IPv6 PIM hello message options········································································· 408
Configuring common IPv6 PIM timers·················································································· 409
Setting the maximum size of a join or prune message····························································· 411
Enabling BFD for IPv6 PIM································································································ 411
Enabling IPv6 PIM passive mode························································································ 411
Enabling IPv6 PIM NSR···································································································· 412
Enabling SNMP notifications for IPv6 PIM············································································· 412
Displaying and maintaining IPv6 PIM ························································································· 413
IPv6 PIM configuration examples ······························································································ 413
IPv6 PIM-DM configuration example···················································································· 413
IPv6 PIM-SM non-scoped zone configuration example···························································· 416
IPv6 PIM-SM admin-scoped zone configuration example························································· 419
IPv6 BIDIR-PIM configuration example ················································································ 425
IPv6 PIM-SSM configuration example·················································································· 429
Troubleshooting IPv6 PIM········································································································ 432
A multicast distribution tree cannot be correctly built ······························································· 432
IPv6 multicast data is abnormally terminated on an intermediate router······································· 432
An RP cannot join an SPT in IPv6 PIM-SM ··········································································· 433
An RPT cannot be built or IPv6 multicast source registration fails in IPv6 PIM-SM························· 433
Document conventions and icons ···················································· 434
Conventions ························································································································· 434
Network topology icons ··········································································································· 435
Support and other resources ·························································· 436
Accessing Hewlett Packard Enterprise Support ············································································ 436
Accessing updates················································································································· 436
Websites ······················································································································· 436
Customer self repair········································································································· 437
Remote support ·············································································································· 437
Documentation feedback ·································································································· 437
Index························································································· 438

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.Aseparate 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, HostAand 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.
Source
Receiver
Receiver
Receiver
Host A
Host B
Host C
Host D
Host E
Packets for all hosts
A network segment

3
Figure 3 Multicast transmission
In Figure 3, the multicast source sends onlyone 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.
•Amulticast 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 thatsupport 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.
Source
Receiver
Receiver
Receiver
Host A
Host B
Host C
Host D
Host E
Packets for the multicast group
IP network

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).
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

5
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 SSMmodel 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.
IP 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—Amulticast 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—Asoftware system thatsupports 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.
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

6
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. For 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.
E Global scope.
Group ID (112 bits)
0xFF Flags Scope
0 7 11 15 31
0RPT

8
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.
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.
XXXX X
XXXX XXXX XXXX XXXX XXXX XXXX
1110 XXXX
0XXX XXXX XXXX XXXX XXXX XXXX
0000 0001 0000 0000 0101 1110
32-bit IPv4 address
48-bit MAC address
5 bits lost
25-bit MAC address prefix
…23 bits
mapped …
FF1E 0000 0000 0000 0000 0000 F30E0101
0101aF30E
48-bit MAC address 3333
32 bits
mapped
128-bit IPv6 address
… …
16-bit MAC
address prefix

9
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 multicastprotocols 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 multicastgroup 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 anAS 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 twoASs. So far, mature solutions include Multicast Source Discovery Protocol
(MSDP) and MBGP. MSDP propagates multicast source information among different ASs.
AS 1 AS 2
Source
Receiver Receiver
Receiver
PIM/IPv6 PIM PIM/IPv6 PIM
MBGP/MSDP
IPv6 MBGP
IGMP/MLD IGMP/MLD
IGMP/MLD

10
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
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
IPv4/IPv6 multicast packets (S1, G1) IPv4/IPv6 multicast packets (S2, G2)
Source 1
Source 2
Receiver
IGMP Snooping
/MLD Snooping
Receiver Receiver
Multicast VLAN
/IPv6 Multicast VLAN
PIM Snooping
/IPv6 PIM Snooping