HPE FlexFabric 5930 Series User manual
HPE FlexFabric 5930 Switch Series
IP Multicast
Configuration Guide
Part number: 5998-7766R
Software version: Release 242x
Document version: 6W100-20151220
© Copyright 2015 Hewlett Packard Enterprise Development LP
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Contents
Multicast overview··························································································· 1
Introduction to multicast ·····································································································································1
Information transmission techniques··········································································································1
Multicast features ·······································································································································3
Common notations in multicast ··················································································································4
Multicast benefits and applications ············································································································4
Multicast models ················································································································································4
Multicast architecture ·········································································································································5
Multicast addresses ···································································································································5
Multicast protocols ·····································································································································9
Multicast packet forwarding mechanism ··········································································································11
Multicast support for VPNs ······························································································································11
Introduction to VPN instances··················································································································11
Multicast application in VPNs···················································································································12
Configuring IGMP snooping·········································································· 13
Overview ··························································································································································13
Basic IGMP snooping concepts ···············································································································13
How IGMP snooping works······················································································································15
Protocols and standards ··························································································································16
IGMP snooping configuration task list··············································································································17
Configuring basic IGMP snooping features ·····································································································17
Enabling IGMP snooping ·························································································································17
Specifying an IGMP snooping version ·····································································································18
Setting the maximum number of IGMP snooping forwarding entries·······················································19
Setting the IGMP last member query interval ··························································································19
Configuring IGMP snooping port features········································································································20
Setting aging timers for dynamic ports·····································································································20
Configuring static ports ····························································································································21
Configuring a port as a simulated member host ······················································································22
Enabling fast-leave processing ················································································································22
Disabling a port from becoming a dynamic router port ············································································23
Configuring the IGMP snooping querier···········································································································23
Configuration prerequisites ······················································································································23
Enabling the IGMP snooping querier ·······································································································23
Configuring parameters for IGMP general queries and responses··························································24
Configuring parameters for IGMP messages···································································································25
Configuration prerequisites ······················································································································25
Configuring source IP addresses for IGMP messages ············································································25
Setting the 802.1p priority for IGMP messages ·······················································································26
Configuring IGMP snooping policies ················································································································26
Configuring a multicast group policy ········································································································27
Configuring multicast source port filtering ································································································27
Enabling dropping unknown multicast data······························································································28
Enabling IGMP report suppression ··········································································································28
Setting the maximum number of multicast groups on a port····································································28
Enabling the multicast group replacement feature···················································································29
Displaying and maintaining IGMP snooping ····································································································29
IGMP snooping configuration examples ··········································································································30
Group policy 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
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Configuring PIM snooping············································································· 39
Overview ··························································································································································39
Configuring PIM snooping································································································································40
Displaying and maintaining PIM snooping ·······································································································40
PIM snooping configuration example···············································································································41
Troubleshooting PIM snooping ························································································································44
PIM snooping does not work on a Layer 2 device ···················································································44
Configuring multicast VLANs ········································································ 45
Overview ··························································································································································45
Multicast VLAN configuration task list ··············································································································47
Configuring a sub-VLAN-based multicast VLAN······························································································47
Configuration prerequisites ······················································································································47
Configuration guidelines···························································································································47
Configuration procedure···························································································································47
Configuring a port-based multicast VLAN ········································································································48
Configuration prerequisites ······················································································································48
Configuring user port attributes················································································································48
Assigning user ports to a multicast VLAN ································································································49
Setting the maximum number of multicast VLAN forwarding entries·······························································49
Displaying and maintaining multicast VLANs···································································································50
Multicast VLAN configuration examples ··········································································································50
Sub-VLAN-based multicast VLAN configuration example ·······································································50
Port-based multicast VLAN configuration example··················································································53
Configuring multicast routing and forwarding················································ 57
Overview ··························································································································································57
RPF check mechanism ····························································································································57
Static multicast routes ······························································································································59
Multicast forwarding across unicast subnets····························································································61
Configuration task list·······································································································································61
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···························································································63
Configuring static multicast MAC address entries····················································································64
Configuring multicast forwarding among sub-VLANs of a super VLAN ···························································64
Displaying and maintaining multicast routing and forwarding ··········································································65
Configuration examples ···································································································································66
Changing an RPF route ···························································································································66
Creating an RPF route ·····························································································································68
Multicast forwarding over a GRE tunnel···································································································70
Troubleshooting multicast routing and forwarding ···························································································73
Static multicast route failure ·····················································································································73
Configuring IGMP ························································································· 74
Overview ··························································································································································74
IGMPv1 overview ·····································································································································74
IGMPv2 enhancements····························································································································75
IGMPv3 enhancements····························································································································76
IGMP support for VPNs····························································································································77
Protocols and standards ··························································································································77
IGMP configuration task list ·····························································································································78
Configuring basic IGMP features ·····················································································································78
Enabling IGMP ·········································································································································78
Specifying an IGMP version·····················································································································78
Configuring a static group member ··········································································································79
Configuring a multicast group policy ········································································································79
Adjusting IGMP performance···························································································································80
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Configuring IGMP query and response parameters·················································································80
Enabling fast-leave processing ················································································································82
Configuring IGMP SSM mappings ···················································································································82
Configuration prerequisites ······················································································································82
Configuration procedure···························································································································83
Enabling IGMP NSR ········································································································································83
Displaying and maintaining IGMP····················································································································83
IGMP configuration examples··························································································································84
Basic IGMP features configuration example ····························································································84
IGMP SSM mapping configuration example ····························································································86
Troubleshooting IGMP ·····································································································································89
No membership information on the receiver-side router ··········································································89
Inconsistent membership information on the routers on the same subnet···············································89
Configuring PIM ···························································································· 91
Overview ··························································································································································91
PIM-DM overview·····································································································································91
PIM-SM overview ·····································································································································93
BIDIR-PIM overview·································································································································97
Administrative scoping overview ············································································································100
PIM-SSM overview·································································································································102
Relationship among PIM protocols ········································································································103
PIM support for VPNs ····························································································································104
Protocols and standards ························································································································104
Configuring PIM-DM ······································································································································104
PIM-DM configuration task list ···············································································································105
Configuration prerequisites ····················································································································105
Enabling PIM-DM ···································································································································105
Enabling the state refresh feature ··········································································································105
Configuring state refresh parameters·····································································································106
Configuring PIM-DM graft retry timer ·····································································································106
Configuring PIM-SM·······································································································································107
PIM-SM configuration task list················································································································107
Configuration prerequisites ····················································································································107
Enabling PIM-SM ···································································································································107
Configuring an RP··································································································································108
Configuring a BSR ·································································································································109
Configuring multicast source registration ·······························································································111
Configuring the switchover to SPT·········································································································111
Configuring BIDIR-PIM ··································································································································112
BIDIR-PIM configuration task list ···········································································································112
Configuration prerequisites ····················································································································112
Enabling BIDIR-PIM ·······························································································································112
Configuring an RP··································································································································113
Configuring a BSR ·································································································································115
Configuring PIM-SSM ····································································································································117
PIM-SSM configuration task list ·············································································································117
Configuration prerequisites ····················································································································117
Enabling PIM-SM ···································································································································117
Configuring the SSM group range··········································································································117
Configuring common PIM features ················································································································118
Configuration task list·····························································································································118
Configuration prerequisites ····················································································································118
Configuring a multicast source policy·····································································································118
Configuring a PIM hello policy················································································································119
Configuring PIM hello message options·································································································119
Configuring common PIM timers············································································································121
Setting the maximum size of each join or prune message·····································································122
Enabling BFD for PIM ····························································································································122
Enabling PIM passive mode···················································································································123
Enabling PIM NSR ·································································································································123
Displaying and maintaining PIM·····················································································································123
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PIM configuration examples···························································································································124
PIM-DM configuration example··············································································································124
PIM-SM non-scoped zone configuration example ·················································································127
PIM-SM admin-scoped zone configuration example··············································································130
BIDIR-PIM configuration example··········································································································135
PIM-SSM configuration example············································································································139
Troubleshooting PIM······································································································································142
A multicast distribution tree cannot be correctly built ·············································································142
Multicast data is abnormally terminated on an intermediate router························································143
An RP cannot join an SPT in PIM-SM····································································································144
An RPT cannot be built or multicast source registration fails in PIM-SM ···············································144
Configuring MSDP ······················································································ 146
Overview ························································································································································146
How MSDP works ··································································································································146
MSDP support for VPNs ························································································································149
Protocols and standards ························································································································150
MSDP configuration task list ··························································································································150
Configuring basic MSDP functions ················································································································150
Configuration prerequisites ····················································································································150
Enabling MSDP······································································································································150
Creating an MSDP peering connection··································································································151
Configuring a static RPF peer ················································································································151
Configuring an MSDP peering connection·····································································································151
Configuration prerequisites ····················································································································151
Configuring the description for an MSDP peer·······················································································151
Configuring an MSDP mesh group ········································································································152
Controlling MSDP peering connections ·································································································152
Configuring SA message-related parameters································································································153
Configuration prerequisites ····················································································································153
Configuring SA message contents·········································································································153
Configuring SA request messages·········································································································154
Configuring SA message policies ··········································································································154
Configuring the SA cache mechanism ···································································································155
Displaying and maintaining MSDP·················································································································156
MSDP configuration examples·······················································································································156
PIM-SM inter-domain multicast configuration ························································································156
Anycast RP configuration·······················································································································161
SA message filtering configuration·········································································································165
Troubleshooting MSDP··································································································································168
MSDP peers stay in disabled state ········································································································169
No SA entries exist in the router's SA message cache··········································································169
No exchange of locally registered (S, G) entries between RPs ·····························································170
Configuring multicast VPN ·········································································· 171
Overview ························································································································································171
MD-VPN overview··································································································································172
Protocols and standards ························································································································175
How MD-VPN works ······································································································································176
Default-MDT establishment····················································································································176
Default-MDT-based delivery ··················································································································178
MDT switchover ·····································································································································181
Inter-AS MD-VPN···································································································································182
Multicast VPN configuration task list ··············································································································183
Configuring MD-VPN ·····································································································································183
Configuration prerequisites ····················································································································184
Enabling IP multicast routing in a VPN instance ····················································································184
Creating the MD for a VPN instance ······································································································184
Specifying the default-group address·····································································································185
Specifying the MD source interface ·······································································································185
Configuring MDT switchover parameters·······························································································185
Enabling data-group reuse logging ········································································································186
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Configuring BGP MDT ···································································································································186
Configuration prerequisites ····················································································································186
Configuring BGP MDT peers or peer groups ·························································································187
Configuring a BGP MDT route reflector ·································································································187
Displaying and maintaining multicast VPN ····································································································188
Multicast VPN configuration examples ··········································································································189
Intra-AS MD-VPN configuration example·······························································································189
Inter-AS MD-VPN configuration example·······························································································201
Troubleshooting MD-VPN ······························································································································214
A default-MDT cannot be established ····································································································214
An MVRF cannot be created··················································································································215
Configuring MLD snooping ········································································· 216
Overview ························································································································································216
Basic MLD snooping concepts···············································································································216
How MLD snooping works ·····················································································································218
Protocols and standards ························································································································219
MLD snooping configuration task list ·············································································································220
Configuring basic MLD snooping features ·····································································································220
Enabling MLD snooping ·························································································································220
Specifying an MLD snooping version·····································································································221
Setting the maximum number of MLD snooping forwarding entries ······················································222
Setting the MLD last listener query interval····························································································222
Configuring MLD snooping port features ·······································································································223
Setting aging timers for dynamic ports···································································································223
Configuring static ports ··························································································································224
Configuring a port as a simulated member host ····················································································225
Enabling fast-leave processing ··············································································································225
Disabling a port from becoming a dynamic router port ··········································································226
Configuring the MLD snooping querier ··········································································································226
Configuration prerequisites ····················································································································226
Enabling the MLD snooping querier·······································································································227
Configuring parameters for MLD general queries and responses ·························································227
Configuring parameters for MLD messages ··································································································228
Configuration prerequisites ····················································································································228
Configuring source IPv6 addresses for MLD messages ········································································228
Setting the 802.1p priority for MLD messages ·······················································································229
Configuring MLD snooping policies ···············································································································230
Configuring an IPv6 multicast group policy ····························································································230
Enabling IPv6 multicast source port filtering ··························································································230
Enabling dropping unknown IPv6 multicast data ···················································································231
Enabling MLD report suppression··········································································································231
Setting the maximum number of IPv6 multicast groups on a port··························································232
Enabling the IPv6 multicast group replacement feature·········································································232
Displaying and maintaining MLD snooping ····································································································233
MLD snooping configuration examples··········································································································234
IPv6 group policy configuration example ·······························································································234
Static port configuration example···········································································································235
MLD snooping querier configuration example························································································238
Troubleshooting MLD snooping ·····················································································································241
Layer 2 multicast forwarding cannot function·························································································241
IPv6 multicast group policy does not work ·····························································································241
Configuring IPv6 PIM snooping ·································································· 242
Overview ························································································································································242
Configuring IPv6 PIM snooping ·····················································································································243
Displaying and maintaining IPv6 PIM snooping·····························································································244
IPv6 PIM snooping configuration example·····································································································244
Troubleshooting IPv6 PIM snooping ··············································································································247
IPv6 PIM snooping does not work on a Layer 2 device ·········································································247
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Configuring IPv6 multicast VLANs ······························································ 249
Overview ························································································································································249
IPv6 multicast VLAN configuration task list····································································································251
Configuring a sub-VLAN-based IPv6 multicast VLAN ···················································································251
Configuration prerequisites ····················································································································251
Configuration guidelines·························································································································251
Configuration procedure·························································································································251
Configuring a port-based IPv6 multicast VLAN······························································································252
Configuration prerequisites ····················································································································252
Configuring user port attributes··············································································································252
Assigning user ports to an IPv6 multicast VLAN····················································································252
Setting the maximum number of IPv6 multicast VLAN forwarding entries·····················································253
Displaying and maintaining IPv6 multicast VLANs ························································································253
IPv6 multicast VLAN configuration examples ································································································254
Sub-VLAN-based IPv6 multicast VLAN configuration example ·····························································254
Port-based IPv6 multicast VLAN configuration example········································································257
Configuring IPv6 multicast routing and forwarding······································ 261
Overview ························································································································································261
RPF check mechanism ··························································································································261
IPv6 multicast forwarding across IPv6 unicast subnets ·········································································263
Configuration task list·····································································································································263
Enabling IPv6 multicast routing······················································································································263
Configuring IPv6 multicast routing and forwarding ························································································264
Specifying the longest prefix match principle ·························································································264
Configuring IPv6 multicast load splitting ································································································264
Configuring an IPv6 multicast forwarding boundary···············································································264
Configuring IPv6 static multicast MAC address entries ·········································································265
Configuring IPv6 multicast forwarding among sub-VLANs of a super VLAN ·········································266
Displaying and maintaining IPv6 multicast routing and forwarding ································································266
Configuration examples ·································································································································267
IPv6 multicast forwarding over a GRE tunnel ························································································267
Configuring MLD ························································································· 271
Overview ························································································································································271
How MLDv1 works ·································································································································271
MLDv2 enhancements ···························································································································273
MLD support for VPNs ···························································································································274
Protocols and standards ························································································································274
MLD configuration task list·····························································································································274
Configuring basic MLD features·····················································································································274
Enabling MLD·········································································································································275
Specifying an MLD version ····················································································································275
Configuring a static group member ········································································································275
Configuring an IPv6 multicast group policy ····························································································276
Adjusting MLD performance ··························································································································276
Configuring MLD query and response parameters ················································································276
Enabling fast-leave processing ··············································································································278
Configuring MLD SSM mappings···················································································································279
Configuration prerequisites ····················································································································279
Configuration procedure·························································································································279
Enabling MLD NSR ········································································································································279
Displaying and maintaining MLD ···················································································································280
MLD configuration examples ·························································································································280
Basic MLD features configuration example····························································································280
MLD SSM mapping configuration example····························································································282
Troubleshooting MLD·····································································································································285
No member information exists on the receiver-side router ····································································285
Inconsistent membership information on the routers on the same subnet·············································286
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Configuring IPv6 PIM ·················································································· 287
Overview ························································································································································287
IPv6 PIM-DM overview···························································································································287
IPv6 PIM-SM overview···························································································································289
IPv6 BIDIR-PIM overview·······················································································································294
IPv6 administrative scoping overview ····································································································297
IPv6 PIM-SSM overview ························································································································299
Relationship among IPv6 PIM protocols ································································································300
IPv6 PIM support for VPNs ····················································································································301
Protocols and standards ························································································································301
Configuring IPv6 PIM-DM ······························································································································301
IPv6 PIM-DM configuration task list ·······································································································302
Configuration prerequisites ····················································································································302
Enabling IPv6 PIM-DM···························································································································302
Enabling the state refresh feature ··········································································································302
Configuring state refresh parameters·····································································································303
Configuring IPv6 PIM-DM graft retry timer ·····························································································303
Configuring IPv6 PIM-SM ······························································································································304
IPv6 PIM-SM configuration task list ·······································································································304
Configuration prerequisites ····················································································································304
Enabling IPv6 PIM-SM ···························································································································304
Configuring an RP··································································································································305
Configuring a BSR ·································································································································306
Configuring IPv6 multicast source registration·······················································································308
Configuring the switchover to SPT·········································································································308
Configuring IPv6 BIDIR-PIM ··························································································································308
IPv6 BIDIR-PIM configuration task list ···································································································309
Configuration prerequisites ····················································································································309
Enabling IPv6 BIDIR-PIM·······················································································································309
Configuring an RP··································································································································310
Configuring a BSR ·································································································································311
Configuring IPv6 PIM-SSM ····························································································································313
IPv6 PIM-SSM configuration task list ·····································································································313
Configuration prerequisites ····················································································································313
Enabling IPv6 PIM-SM ···························································································································313
Configuring the IPv6 SSM group range ·································································································314
Configuring common IPv6 PIM features ········································································································314
Configuration task list·····························································································································314
Configuration prerequisites ····················································································································315
Configuring an IPv6 multicast source policy ··························································································315
Configuring an IPv6 PIM hello policy ·····································································································315
Configuring IPv6 PIM hello message options ························································································316
Configuring common IPv6 PIM timers····································································································317
Setting the maximum size of each join or prune message·····································································318
Enabling BFD for IPv6 PIM ····················································································································319
Enabling IPv6 PIM passive mode ··········································································································319
Enabling IPv6 PIM NSR ·························································································································320
Displaying and maintaining IPv6 PIM ············································································································320
IPv6 PIM configuration examples ··················································································································321
IPv6 PIM-DM configuration example······································································································321
IPv6 PIM-SM non-scoped zone configuration example ·········································································324
IPv6 PIM-SM admin-scoped zone configuration example ·····································································327
IPv6 BIDIR-PIM configuration example··································································································333
IPv6 PIM-SSM configuration example ···································································································337
Troubleshooting IPv6 PIM······························································································································340
A multicast distribution tree cannot be correctly built ·············································································340
IPv6 multicast data is abnormally terminated on an intermediate router ···············································341
An RP cannot join an SPT in IPv6 PIM-SM ···························································································342
An RPT cannot be built or IPv6 multicast source registration fails in IPv6 PIM-SM·······························342
viii
Document conventions and icons ······························································· 344
Conventions ···················································································································································344
Network topology icons··································································································································345
Support and other resources ······································································ 346
Accessing Hewlett Packard Enterprise Support ····························································································346
Accessing updates·········································································································································346
Websites ················································································································································347
Customer self repair·······························································································································347
Remote support······································································································································347
Documentation feedback ·······················································································································347
Index ··········································································································· 348
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 not as efficient as multicast for sending data to groups of hosts.
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 multicast receivers 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 use 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. A multicast source 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.
Therefore, receivers can receive 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 ASM and SFM
models use a different multicast address range than the SSM 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—Multicast receivers 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 multicast receivers. The TCP/IP stack
must support reception and transmission of multicast data.
Multicast addresses
IP multicast addresses
•IPv4 multicast addresses:
IANA assigns 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 mapped from 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 An example of IPv6-to-MAC address mapping
IMPORTANT:
Because of the duplicate mapping from multicast IP address to multicast MAC address, the device
might inadvertently send multicast protocol packets as multicast data in Layer 2 forwarding. To avoid
this, do not use the IP multicast addresses that are mapped to multicast MAC addresses
0100-5E00-00xx and 3333-0000-00xx (where "x" specifies any hexadecimal number from 0 to F).
9
Multicast protocols
Multicast protocols include the following categories:
•Layer 3 and Layer 2 multicast protocols:
{Layer 3 multicast refers to IP multicast working 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 working 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 the 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.
10
In the ASM model, multicast routes include intra-domain routes and inter-domain routes.
{An intra-domain multicast routing protocol discovers multicast sources and builds multicast
distribution trees within an AS to deliver multicast data to receivers. Among a variety of
mature intra-domain multicast routing protocols, PIM is most widely used. Based on the
forwarding mechanism, PIM has dense mode (often referred to as PIM-DM) and sparse
mode (often referred to as PIM-SM).
{An inter-domain multicast routing protocol is used for delivering multicast information
between two ASs. So far, mature solutions include Multicast Source Discovery Protocol
(MSDP) and MBGP. MSDP propagates multicast source information among different ASs.
MBGP is an extension of the MP-BGP for exchanging multicast routing information among
different ASs.
For the SSM model, multicast routes are not divided into intra-domain routes and inter-domain
routes. Because receivers know the positions of the multicast sources, channels established
through PIM-SM are sufficient for the transport of multicast information.
Layer 2 multicast protocols
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 run on Layer 2 devices as multicast constraining
mechanisms to improve multicast forwarding efficiency. They generate Layer 2 multicast
forwarding tables by listening to 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 on a multicast network where
multicast receivers for the same group exist in different VLANs. With these protocols, the Layer
3 multicast device sends only one copy of multicast to the multicast VLAN or IPv6 multicast
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