HPP Enterprises FlexNetwork 7500 Configuration Manual

HPE FlexNetwork 7500 Switch Series

IP Multicast Configuration Guide

P Software Document version: 6W100-20161230

art number: 5200-1936

version: 7500-CMW710-R7524

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Acknowledgments

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Contents

Multicast overview ························································································· 1

Introduction to multicast ····································································································································· 1

Information transmission techniques ·········································································································· 1 Multicast features ······································································································································· 3 Common notations in multicast ·················································································································· 4

Multicast benefits and applications ············································································································ 4 Multicast models ················································································································································ 4 Multicast architecture ········································································································································· 5

Multicast addresses ··································································································································· 5

Multicast protocols ····································································································································· 8 Multicast packet forwarding mechanism ·········································································································· 10 Multicast support for VPNs······························································································································· 11

Introduction to VPN instances ·················································································································· 11

Multicast application in VPNs ··················································································································· 12

Configuring IGMP snooping ········································································· 13

IGMP snooping ports ······························································································································· 13

How IGMP snooping works ······················································································································ 15

IGMP snooping proxying ·························································································································· 16

Protocols and standards ·························································································································· 17

Configuration restrictions and guidelines ································································································· 17 IGMP snooping configuration task list ·············································································································· 17

IGMP snooping configuration task list for VLANs ···················································································· 18

IGMP configuration task list for VSIs········································································································ 18 Configuring basic IGMP snooping features ····································································································· 19

Enabling IGMP snooping ························································································································· 19

Specifying an IGMP snooping version ····································································································· 20

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 ······················································································································ 26

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 the source IP address 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 ······························································································································ 34 Displaying and maintaining IGMP snooping ···································································································· 34 IGMP snooping configuration examples ·········································································································· 36

Group policy and simulated joining configuration example (for VLANs) ·················································· 36

Static port configuration example (for VLANs) ························································································· 38

IGMP snooping querier configuration example (for VLANs) ···································································· 40

IGMP snooping proxying configuration example (for VLANs) ·································································· 43

IGMP snooping configuration example (for VXLANs) ·············································································· 44 Troubleshooting IGMP snooping ····················································································································· 49

Layer 2 multicast forwarding cannot function ··························································································· 49

Multicast group policy does not work ······································································································· 50

Configuring PIM snooping ············································································ 51

Overview ·························································································································································· 51 Configuring PIM snooping ································································································································ 52 Displaying and maintaining PIM snooping ······································································································· 53 PIM snooping configuration example ··············································································································· 53

Network requirements ······························································································································ 53

Configuration procedure ··························································································································· 54

Verifying the configuration ························································································································ 55 Troubleshooting PIM snooping ························································································································ 57

PIM snooping does not work on a Layer 2 device ··················································································· 57

Configuring multicast VLANs ······································································· 58

Overview ·························································································································································· 58 Multicast VLAN configuration task list ·············································································································· 60 Configuring a sub-VLAN-based multicast VLAN ······························································································ 60

Configuration prerequisites ······················································································································ 60

Configuration restrictions and guidelines ································································································· 60

Configuration procedure ··························································································································· 61 Configuring a port-based multicast VLAN ········································································································ 61

Configuration prerequisites ······················································································································ 61

Configuring user port attributes ················································································································ 61

Assigning user ports to a multicast VLAN ································································································ 62 Setting the maximum number of multicast VLAN forwarding entries ······························································· 62 Displaying and maintaining multicast VLANs ··································································································· 63 Multicast VLAN configuration examples ·········································································································· 63

Sub-VLAN-based multicast VLAN configuration example ······································································· 63

Port-based multicast VLAN configuration example ·················································································· 66

Configuring multicast routing and forwarding ··············································· 70

RPF check mechanism ···························································································································· 70

Static multicast routes ······························································································································ 72

Multicast forwarding across unicast subnets ···························································································· 73 Configuration task list ······································································································································· 74 Enabling IP multicast routing···························································································································· 74 Configuring multicast routing and forwarding ··································································································· 75

Configuring static multicast routes ··········································································································· 75

Specifying the longest prefix match principle ··························································································· 75

Configuring multicast load splitting··········································································································· 76

Configuring a multicast forwarding boundary ··························································································· 76 Enabling multicast forwarding between sub-VLANs of a super VLAN ····························································· 76 Displaying and maintaining multicast routing and forwarding ·········································································· 77 Configuration examples ··································································································································· 79

Changing an RPF route ··························································································································· 79

Creating an RPF route ····························································································································· 81

Multicast forwarding over a GRE tunnel ··································································································· 82 Troubleshooting multicast routing and forwarding ··························································································· 85

Static multicast route failure ····················································································································· 85

Configuring IGMP ························································································ 86

IGMPv1 overview ····································································································································· 86

IGMPv2 enhancements ···························································································································· 87

IGMPv3 enhancements ···························································································································· 88

IGMP SSM mapping ································································································································ 89

IGMP proxying ········································································································································· 90

IGMP support for VPNs ···························································································································· 91

Protocols and standards ·························································································································· 91 IGMP configuration task list ····························································································································· 92 Configuring basic IGMP features ····················································································································· 92

Enabling IGMP ········································································································································· 92

Specifying an IGMP version ····················································································································· 93

Configuring a static group member ·········································································································· 93

Configuring a multicast group policy ········································································································ 93 Adjusting IGMP performance ··························································································································· 94

Configuring IGMP query and response parameters ················································································· 94

Enabling fast-leave processing ················································································································ 96 Configuring IGMP SSM mappings ··················································································································· 97

Configuration prerequisites ······················································································································ 97

Configuration procedure ··························································································································· 97 Configuring IGMP proxying ······························································································································ 97

Enabling IGMP proxying ·························································································································· 97

Enabling multicast forwarding on a non-querier interface ········································································ 98

Configuring multicast load splitting on an IGMP proxy············································································· 98 Enabling IGMP NSR ········································································································································ 99 Displaying and maintaining IGMP ···················································································································· 99 IGMP configuration examples ························································································································ 100

Basic IGMP features configuration examples ························································································ 100

IGMP SSM mapping configuration example ·························································································· 102

IGMP proxying configuration example ··································································································· 105 Troubleshooting IGMP ··································································································································· 106

No membership information on the receiver-side router ········································································ 106

Inconsistent membership information on the routers on the same subnet············································· 106

Configuring PIM ························································································· 108

PIM-DM overview ··································································································································· 108

PIM-SM overview ··································································································································· 110

BIDIR-PIM overview ······························································································································· 116

Administrative scoping overview ············································································································ 119

PIM-SSM overview ································································································································· 121

Relationship among PIM protocols ········································································································ 122

PIM support for VPNs ···························································································································· 123

Protocols and standards ························································································································ 123 Configuring PIM-DM······································································································································· 123

PIM-DM configuration task list ··············································································································· 124

Configuration prerequisites ···················································································································· 124

Enabling PIM-DM ··································································································································· 124

Enabling the state refresh feature ·········································································································· 124

Configuring state refresh parameters ····································································································· 125

Configuring PIM-DM graft retry timer ····································································································· 125 Configuring PIM-SM ······································································································································· 126

PIM-SM configuration task list················································································································ 126

Configuration prerequisites ···················································································································· 126

Enabling PIM-SM ··································································································································· 126

Configuring an RP ·································································································································· 127

Configuring a BSR ································································································································· 129

Configuring multicast source registration ······························································································· 131

Configuring the switchover to SPT ········································································································· 132

Configuration restrictions and guidelines ······························································································· 132

BIDIR-PIM configuration task list ··········································································································· 132

Configuration prerequisites ···················································································································· 133

Enabling BIDIR-PIM ······························································································································· 133

Configuring an RP ·································································································································· 133

Configuring a BSR ································································································································· 135

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Configuring PIM-SSM ···································································································································· 137

PIM-SSM configuration task list ············································································································· 138

Configuration prerequisites ···················································································································· 138

Enabling PIM-SM ··································································································································· 138

Configuring the SSM group range ·········································································································· 138 Configuring common PIM features················································································································· 139

Configuration task list ····························································································································· 139

Configuration prerequisites ···················································································································· 139

Configuring a multicast source policy ····································································································· 139

Configuring a PIM hello policy················································································································ 140

Configuring PIM hello message options ································································································· 140

Configuring common PIM timers ············································································································ 142

Setting the maximum size of a join or prune message ·········································································· 143

Enabling BFD for PIM ···························································································································· 143

Enabling PIM passive mode ··················································································································· 143

Enabling PIM NSR ································································································································· 144

Enabling SNMP notifications for PIM ····································································································· 144

Setting a DSCP value for outgoing PIM messages ················································································ 144 Displaying and maintaining PIM ····················································································································· 145 PIM configuration examples ··························································································································· 145

PIM-DM configuration example ·············································································································· 145

PIM-SM non-scoped zone configuration example ················································································· 148

PIM-SM admin-scoped zone configuration example·············································································· 151

BIDIR-PIM configuration example ·········································································································· 156

PIM-SSM configuration example············································································································ 160 Troubleshooting PIM ······································································································································ 163

A multicast distribution tree cannot be correctly built ············································································· 163

Multicast data is abnormally terminated on an intermediate router························································ 164

An RP cannot join an SPT in PIM-SM ···································································································· 164

An RPT cannot be built or multicast source registration fails in PIM-SM ··············································· 164

Configuring MSDP ····················································································· 166

How MSDP works ·································································································································· 166

MSDP support for VPNs ························································································································ 171

Protocols and standards ························································································································ 171 MSDP configuration task list ·························································································································· 172 Configuring basic MSDP features ·················································································································· 172

Configuration prerequisites ···················································································································· 172

Enabling MSDP ······································································································································ 172

Specifying an MSDP peer ······················································································································ 173

Configuring a static RPF peer ················································································································ 173 Configuring an MSDP peering connection ····································································································· 173

Configuration prerequisites ···················································································································· 173

Configuring a description for an MSDP peer ·························································································· 174

Configuring an MSDP mesh group ········································································································ 174

Controlling MSDP peering connections ································································································· 174 Configuring SA message-related parameters ································································································ 175

Configuration prerequisites ···················································································································· 175

Enabling multicast data encapsulation in SA messages ········································································ 175

Configuring the originating RP of SA messages ···················································································· 176

Configuring SA request messages ········································································································· 176

Configuring SA message policies ·········································································································· 177

Configuring the SA cache mechanism ··································································································· 178 Enabling MSDP NSR ····································································································································· 178 Displaying and maintaining MSDP ················································································································· 178 MSDP configuration examples ······················································································································· 179

PIM-SM inter-domain multicast configuration ························································································ 179

Inter-AS multicast configuration by leveraging static RPF peers ··························································· 184

Anycast RP configuration ······················································································································· 188

SA message filtering configuration ········································································································· 192 Troubleshooting MSDP ·································································································································· 195

MSDP peers stay in disabled state ········································································································ 196

No SA entries exist in the router's SA message cache ·········································································· 196

No exchange of locally registered (S, G) entries between RPs ····························································· 196

Configuring multicast VPN ········································································· 197

MD VPN overview ·································································································································· 198

Protocols and standards ························································································································ 201 How MD VPN works······································································································································· 201

Default-MDT establishment ···················································································································· 202

Default-MDT-based delivery ·················································································································· 205

MDT switchover ····································································································································· 208

Inter-AS MD VPN ··································································································································· 209 Configuration restrictions and guidelines ······································································································· 212 Multicast VPN configuration task list ·············································································································· 212 Configuring MD VPN ······································································································································ 213

Configuration prerequisites ···················································································································· 213

Enabling IP multicast routing for a VPN instance ··················································································· 213

Creating an MD for a VPN instance ······································································································· 214

Create an MD address family················································································································· 214

Specifying the default-group ·················································································································· 215

Specifying the MD source interface ······································································································· 215

Configuring MDT switchover parameters ······························································································· 216

Configuring the RPF vector feature ········································································································ 216

Enabling data-group reuse logging ········································································································ 217 Configuring BGP MDT ··································································································································· 217

Configuration prerequisites ···················································································································· 217

Configuring BGP MDT peers or peer groups ························································································· 217

Configuring a BGP MDT route reflector ································································································· 218 Displaying and maintaining multicast VPN····································································································· 219 Multicast VPN configuration examples··········································································································· 219

Intra-AS MD VPN configuration example ······························································································· 219

MD VPN inter-AS option B configuration example ················································································· 233

MD VPN inter-AS option C configuration example ················································································· 247 Troubleshooting MD VPN ······························································································································ 260

A default-MDT cannot be established ···································································································· 260

An MVRF cannot be created ·················································································································· 260

Configuring MLD snooping ········································································ 262

MLD snooping ports ······························································································································· 262

How MLD snooping works ····················································································································· 264

MLD snooping proxying ························································································································· 265

Protocols and standards ························································································································ 266 Configuration restrictions and guidelines ······································································································· 266 MLD snooping configuration task list ············································································································· 267

MLD snooping configuration task list for VLANs ···················································································· 267

MLD snooping configuration task list for VSIs························································································ 267 Configuring basic MLD snooping features ····································································································· 268

Enabling MLD snooping ························································································································· 268

Specifying an MLD snooping version ····································································································· 269

Setting the maximum number of MLD snooping forwarding entries ······················································ 270

Configuring static IPv6 multicast MAC address entries ········································································· 270

Setting the MLD last listener query interval ···························································································· 271 Configuring MLD snooping port features ······································································································· 271

Setting aging timers for dynamic ports ··································································································· 272

Configuring static ports ·························································································································· 272

Configuring a port as a simulated member host ···················································································· 273

Enabling fast-leave processing ·············································································································· 273

Disabling a port from becoming a dynamic router port ·········································································· 274 Configuring the MLD snooping querier ·········································································································· 275

Configuration prerequisites ···················································································································· 275

Enabling the MLD snooping querier ······································································································· 275

Configuring parameters for MLD general queries and responses ························································· 276 Enabling MLD snooping proxying ·················································································································· 276 Configuring parameters for MLD messages ·································································································· 277

Configuration prerequisites ···················································································································· 277

Configuring source IPv6 addresses for MLD messages ········································································ 277

Setting the 802.1p priority for MLD messages ······················································································· 279 Configuring MLD snooping policies················································································································ 279

Configuring an IPv6 multicast group policy ···························································································· 280

Enabling IPv6 multicast source port filtering ·························································································· 280

Enabling dropping unknown IPv6 multicast data ··················································································· 281

Enabling MLD report suppression ·········································································································· 282

Setting the maximum number of IPv6 multicast groups on a port ·························································· 282

Enabling IPv6 multicast group replacement ··························································································· 282

Enabling host tracking ···························································································································· 283 Displaying and maintaining MLD snooping ···································································································· 284 MLD snooping configuration examples ·········································································································· 285

IPv6 group policy and simulated joining configuration example (for VLANs) ········································· 285

Static port configuration example (for VLANs) ······················································································· 287

MLD snooping querier configuration example (for VLANs) ···································································· 290

MLD snooping proxying configuration example (for VLANs) ································································· 293

MLD snooping configuration example (for VXLANs)·············································································· 294 Troubleshooting MLD snooping ····················································································································· 299

Layer 2 multicast forwarding cannot function ························································································· 299

IPv6 multicast group policy does not work ····························································································· 300

Configuring IPv6 PIM snooping ································································· 301

Overview ························································································································································ 301 Configuring IPv6 PIM snooping······················································································································ 302 Displaying and maintaining IPv6 PIM snooping ····························································································· 303 IPv6 PIM snooping configuration example (for VLANs) ················································································· 303

Network requirements ···························································································································· 303

Configuration procedure ························································································································· 304

Verifying the configuration ······················································································································ 306 Troubleshooting IPv6 PIM snooping ·············································································································· 307

IPv6 PIM snooping does not work on a Layer 2 device ········································································· 307

Configuring IPv6 multicast VLANs ····························································· 308

Overview ························································································································································ 308 IPv6 multicast VLAN configuration task list ···································································································· 310 Configuring a sub-VLAN-based IPv6 multicast VLAN ··················································································· 310

Configuration prerequisites ···················································································································· 310

Configuration guidelines ························································································································· 310

Configuration procedure ························································································································· 311 Configuring a port-based IPv6 multicast VLAN ······························································································ 311

Configuration prerequisites ···················································································································· 311

Configuring user port attributes ·············································································································· 311

Assigning user ports to an IPv6 multicast VLAN ···················································································· 312 Setting the maximum number of IPv6 multicast VLAN forwarding entries ····················································· 312 Displaying and maintaining IPv6 multicast VLANs························································································· 313 IPv6 multicast VLAN configuration examples ································································································ 313

Sub-VLAN-based IPv6 multicast VLAN configuration example ····························································· 313

Port-based IPv6 multicast VLAN configuration example········································································ 316

Configuring IPv6 multicast routing and forwarding ····································· 320

RPF check mechanism ·························································································································· 320

IPv6 multicast forwarding across IPv6 unicast subnets ········································································· 322 Configuration task list ····································································································································· 322 Enabling IPv6 multicast routing ······················································································································ 322 Configuring IPv6 multicast routing and forwarding························································································· 323

Specifying the longest prefix match principle ························································································· 323

Configuring IPv6 multicast load splitting ································································································ 323

Configuring an IPv6 multicast forwarding boundary··············································································· 323

Enabling IPv6 multicast forwarding between sub-VLANs of a super VLAN ··········································· 324 Displaying and maintaining IPv6 multicast routing and forwarding ································································ 324 IPv6 multicast routing and forwarding configuration example ········································································ 326

Network requirements ···························································································································· 326

Configuration procedure ························································································································· 327

Verifying the configuration ······················································································································ 328

Configuring MLD ························································································ 330

How MLDv1 works ································································································································· 330

MLDv2 enhancements ··························································································································· 332

MLD SSM mapping ································································································································ 333

MLD proxying ········································································································································· 334

MLD support for VPNs ··························································································································· 334

Protocols and standards ························································································································ 334 MLD configuration task list ····························································································································· 335 Configuring basic MLD features ····················································································································· 335

Enabling MLD ········································································································································· 335

Specifying an MLD version ···················································································································· 336

Configuring a static group member ········································································································ 336

Configuring an IPv6 multicast group policy ···························································································· 336 Adjusting MLD performance··························································································································· 337

Configuring MLD query and response parameters ················································································ 337

Enabling fast-leave processing ·············································································································· 339 Configuring MLD SSM mappings ··················································································································· 339

Configuration prerequisites ···················································································································· 340

Configuration procedure ························································································································· 340 Configuring MLD proxying······························································································································ 340

Enabling MLD proxying ·························································································································· 340

Enabling IPv6 multicast forwarding on a non-querier interface ······························································ 341

Configuring IPv6 multicast load splitting on an MLD proxy ···································································· 341 Enabling MLD NSR ········································································································································ 342 Displaying and maintaining MLD···················································································································· 342 MLD configuration examples·························································································································· 342

Basic MLD features configuration examples ·························································································· 342

MLD SSM mapping configuration example ···························································································· 345

MLD proxying configuration example ····································································································· 347 Troubleshooting MLD ····································································································································· 349

No member information exists on the receiver-side router ···································································· 349

Inconsistent membership information on the routers on the same subnet············································· 349

Configuring IPv6 PIM ················································································· 350

IPv6 PIM-DM overview ··························································································································· 350

IPv6 PIM-SM overview ··························································································································· 352

IPv6 BIDIR-PIM overview ······················································································································· 358

IPv6 administrative scoping overview ···································································································· 361

IPv6 PIM-SSM overview ························································································································ 363

Relationship among IPv6 PIM protocols ································································································ 364

IPv6 PIM support for VPNs ···················································································································· 365

Protocols and standards ························································································································ 365 Configuring IPv6 PIM-DM ······························································································································ 365

IPv6 PIM-DM configuration task list ······································································································· 366

Configuration prerequisites ···················································································································· 366

Enabling IPv6 PIM-DM ··························································································································· 366

Enabling the state refresh feature ·········································································································· 366

Configuring state refresh parameters ····································································································· 367

Configuring IPv6 PIM-DM graft retry timer ····························································································· 367 Configuring IPv6 PIM-SM······························································································································· 368

vii

IPv6 PIM-SM configuration task list ······································································································· 368

Configuration prerequisites ···················································································································· 368

Enabling IPv6 PIM-SM ··························································································································· 368

Configuring an RP ·································································································································· 369

Configuring a BSR ································································································································· 371

Configuring IPv6 multicast source registration ······················································································· 373

Configuring the switchover to SPT ········································································································· 374 Configuring IPv6 BIDIR-PIM ·························································································································· 374

Configuration restrictions and guidelines ······························································································· 374

IPv6 BIDIR-PIM configuration task list ··································································································· 374

Configuration prerequisites ···················································································································· 375

Enabling IPv6 BIDIR-PIM ······················································································································· 375

Configuring an RP ·································································································································· 375

Configuring a BSR ································································································································· 377 Configuring IPv6 PIM-SSM ···························································································································· 379

IPv6 PIM-SSM configuration task list ····································································································· 379

Configuration prerequisites ···················································································································· 380

Enabling IPv6 PIM-SM ··························································································································· 380

Configuring the IPv6 SSM group range ································································································· 380 Configuring common IPv6 PIM features ········································································································ 381

Configuration task list ····························································································································· 381

Configuration prerequisites ···················································································································· 381

Configuring an IPv6 multicast source policy ·························································································· 381

Configuring an IPv6 PIM hello policy ····································································································· 382

Configuring IPv6 PIM hello message options ························································································ 382

Configuring common IPv6 PIM timers ···································································································· 383

Setting the maximum size of a join or prune message ·········································································· 385

Enabling BFD for IPv6 PIM ···················································································································· 385

Enabling IPv6 PIM passive mode ·········································································································· 385

Enabling IPv6 PIM NSR ························································································································· 386

Enabling SNMP notifications for IPv6 PIM ····························································································· 386 Displaying and maintaining IPv6 PIM············································································································· 387 IPv6 PIM configuration examples··················································································································· 387

IPv6 PIM-DM configuration example ······································································································ 387

IPv6 PIM-SM non-scoped zone configuration example ········································································· 390

IPv6 PIM-SM admin-scoped zone configuration example ····································································· 393

IPv6 BIDIR-PIM configuration example ·································································································· 399

IPv6 PIM-SSM configuration example ··································································································· 403 Troubleshooting IPv6 PIM ······························································································································ 406

A multicast distribution tree cannot be correctly built ············································································· 406

IPv6 multicast data is abnormally terminated on an intermediate router ··············································· 406

An RP cannot join an SPT in IPv6 PIM-SM ··························································································· 407

An RPT cannot be built or IPv6 multicast source registration fails in IPv6 PIM-SM ······························· 407

Document conventions and icons ······························································ 408

Conventions ··················································································································································· 408 Network topology icons ·································································································································· 409

Support and other resources ····································································· 410

Accessing Hewlett Packard Enterprise Support····························································································· 410 Accessing updates ········································································································································· 410

Websites ················································································································································ 411

Customer self repair ······························································································································· 411

Remote support ······································································································································ 411

Documentation feedback ······················································································································· 411

Index ·········································································································· 413

viii

Multicast overview

Source

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

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 transmis sion, the information sourc e must send a se parate copy of inform ation to each host that needs the inf ormation.

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. I f a large number of hosts need t he information, the inf ormation source must send a separate copy of the same inform ation 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.

Broadcast

Source

Receiver

Host A

Host B

Host C

Host D

Host E

Packets for all hosts

A network segment

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

Multicast

In Figure 2, only Host B, Host D, and Host E need the information. If the information is broadcast to the subnet, Host A and Host C also receive it. In addition to information security issues, broadcasting to hosts that do not need the information also causes traffic flooding on the same subnet.

Broadcast is disadvantageous in transmitting data to specific hosts. Moreover, broadcast transmission is a significant waste of network resources.

Multicast provides point-to-m ultipoint data transmissions with the minimum networ k consumption. When some hosts on the n etwork need multicast inf ormation, the inform ation 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.

Figure 3 Multicast transmission

•

Source

Receiver

Host A

Host B

Host C

Host D

Host E

Packets for the multicast group

IP network

The multicast source s ends only one copy of the inf ormation to a m ulticast group. Host B, Hos t D, and Host E, which are information receivers, must join the multicast group. The routers on the network duplicate and forward the information based on the distribution of the group members. Finally, the information is correctly delivered to Host B, Host D, and Host E.

To summarize, multicast has the following advantages:

Advantages over unicast—Multicast data is replicated and distributed until it flows to the

farthest-possible node from the source. The increase of receiver hosts will not remarkably increase the load of the source or the usage of network resources.

Advantages over broadcast—Multicast data is sent only to the receivers that need it. This

saves network bandwidth and enhances network security. In addition, multicast data is not confined to the same subnet.

Multicast features

A multicast group is a multicast receiver set identified by an IP multicast address. Hosts must

join a multicast group to become members of the multicast group before they receive the multicast data addressed to that multicast group. Typically, a multicast source does not need to join a multicast group.

A multicast source is an information sender. It can send data to multiple multicast groups at the

same time. Multiple multicast sources can send data to the same multicast group at the same time.

The group memberships are dynamic. Hosts can join or leave multicast groups at any time.

Multicast groups are not subject to geographic restrictions.

Multicast routers or Layer 3 multicast devices are routers or Layer 3 switches that support Layer

3 multicast. They provide multicast routing and manage multicast group memberships on stub subnets with attached grou p members. A multicast router itself can be a multicast group member.

For a better understandi ng of the m ulticas t c onc ep t, you can compare multic ast tr ans mission to the transmission of TV programs.

Table 1 Comparing TV program transmission and multicast transmissio n

TV program transmission

Multicast transmission

•

A TV station transmits a TV program through a channel.

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 user turns off the TV set or tunes to another

channel.

A multicast source sends multicast data to a multicast group.

The receiver starts to receive the multicast data sent by the source to the multicast group.

The receiver leaves the multicast group or joins another group.

Common notations in m ulticast

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 inf ormation about the c oncepts 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 th e receivers treat th e multicast sources, the multicast m odels 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 infor mation to a multicast gr o up. R eceivers can join a multicast group and get multicast inform ation addressed to that multicast group from any

multicast sources. In this m odel, receivers do not know the positions of the multicast sources in

•

Address block

Description

maintenance, and so on. Table 3 lists com mon per mane nt

advance.

SFM model

The SFM model is deri ved from the ASM model. To a multicast source, the two models appear to have the same multicast membership architecture.

The SFM model func tionall y extends t he ASM model. The upper-layer software c hecks the source address of received multicast pack ets and perm its or d enies m ulticast t raffic 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 t he y are interes ted.

In the SSM model, receivers have already determined the locations of the multicast sources. This is the main difference between the SSM model and the ASM model. In addition, the SSM model uses a different multicast address r ange than the ASM/SFM model. Dedic ated multicast forwarding paths are established between receivers and the specified multicast sources.

Multicast architecture

IP multicast addresses the following issues:

Where should the multicast source transmit information to? (Multicast addressing.) What receivers exist on the network? (Host registration.) Where is the multicast source that will provide data to the receivers? (Multicast source

discovery.)

How is the information transmitted to the receivers? (Multicast routing.)

IP multicast is an end-to-end service. The multicast architecture involves the following parts:

Addressing mechanism—A multicast source sends information to a group of receivers

through a multicast address.

Host registration—Receiver hosts can join and leave multicast groups dynamically. This

mechanism is the basis for management of group memberships.

Multicast routing—A multicast distribution tree (a forwarding path tree for multicast data on the

network) is constructed for delivering multicast data from a multicast source to receivers.

Multicast applications—A software system that supports multicast applications, such as video

conferencing, must be installed on multicast sources and receiver hosts. The TCP/IP stack must support reception and transmission of multicast data.

Multicast addresses

IP multicast addresses

IPv4 multicast addresses:

IANA assigned the Class D address block (224.0.0.0 to 239.255.255.255) to IPv4 multicast.

Table 2 Class D IP address blocks and 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 addre sses can be use d by routing protocols and for topology searching, protocol

Address block

Description

group addresses. A packet destined for an address in this block will not be forw arded b eyond the l ocal subnet r egard les s

224.0.1.0 to 238.255.255.255

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.

Address

Description

•

239.0.0.0 to 239.255.255.255

of the TTL value in the IP header. 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 addr esses.

Administratively scoped multicast addresses. These addresses are considered locally unique rather than global ly unique. You can reuse them in domains administered by different organizations without causing conflicts. For more information, see RFC 2365.

Table 3 Common permanent multicast group addresses

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:

Figure 4 IPv6 multicast format

Bit

Description

Value

Meaning

Group ID (112 bits)

0xFF

Flags

Scope

0 7 11 15 31

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

0 Reserved, set to 0.

• 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.)

• 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 un icast p refix . (The T bit must a lso be set to 1.)

• 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

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.

•

XXXX X

XXXX XXXX

1110 XXXX

0XXX XXXX

XXXX XXXX

0000 0001

0000 0000

0101 1110

32-bit IPv4 address

48-bit MAC address

5 bits lost

bit MAC address prefix

…

23 bits

mapped

…

FF1E 0000 0000 0000 0000 0000 F30E 0101

0101aF30E

48-bit MAC address

3333

32 bits

mapped

128-bit IPv6 address

… …

16-bit MAC

address prefix

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.

Table 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 rec eive 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.

Table 7 IPv6-to-MAC address mapping

Multicast protoc ol s

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 2 multicast refers to IP multicast operating at the data link layer.

Layer 3 multicast protocols—IGMP, MLD, PIM, IPv6 PIM, MSDP, MBGP, and IPv6 MBGP.

Layer 2 multicast protocols—IGMP snooping, MLD snooping, PIM snooping, IPv6 PIM

•

AS 1 AS 2

Source

Receiver

PIM/IPv6 PIM

MBGP/MSDP

IPv6 MBGP

IGMP/MLD

IGMP

/MLD

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 o nly general descriptions a bout applications and f unc t ions 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 pro tocols include multicast group managem ent protocols and multicast routing protocols.

Figure 6 Positions of Layer 3 multicast protocols

Multicast group management protocols:

Multicast routing 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.

A multicast routing protocol runs on Layer 3 multicast devices to establish and maintain multicast routes and correctly and efficiently forward multicast packets. Multicast routes constitute loop-free data transmission paths (also known as multicast distribution trees) from a data source to multiple receivers.

In the ASM model, multicast routes include intra-domain routes and inter-domain routes.

 An intra-domain multicast routing protocol discovers multicast sources and builds multicast

distribution trees within an AS to deliver multicast data to receivers. Among a variety of mature intra-domain multicast routing protocols, PIM is most widely used. Based on the forwarding mechanism, PIM has dense mode (often referred to as PIM-DM) and sparse mode (often referred to as PIM-SM).

 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

•

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

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 transpor t 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 7 Positions of Layer 2 multicast pro to cols

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 ide ntified by the same m ulticast group address . To deliver multicast packets to these receivers, a multicast source encapsulates the multicast data in an IP packet with the multicast group address as the destination address. Multicast routers on the forwarding paths forward

multicast packets that an incoming interface receives through multiple outgoing interfaces.

•

VPN A

VPN BVPN B

Public network

PE 1

PE 3

CE b3

CE a2

CE a3

CE b

CE a

CE b2

Compared to a unicast model, a multicast model is more complex in the following aspects:

To ensure multicast packet transmission on the network, different routing tables are used to

guide multicast forwarding. These routing tables include unicast routing tables, routing tables for multicast (for example, the MBGP routing table), and static multicast routing tables.

T o process the same multicast information from different peers received on different interfaces,

the multicast device performs an RPF check on each multicast packet. The RPF check result determines whether the packet will be forwarded or discarded. The RPF check mechanism is the basis for most multicast routing protocols to implement multicast forwarding.

For more information about the RPF mechanism, see "Configuring multicast routing and forwarding" and "Configuring IPv6 multicast routing and forwarding."

Multicast support for VPNs

Multicast support for VPNs refers to multicast applied in VPNs.

Introduction to VPN instances

VPNs are isolated from one another and from the public network. As shown in Figure 8, VPN A and VPN B separately access the public network through PE devices.

Figure 8 VPN networking diagram

The P device belongs to the public network. The CE devices belong to their respective VPNs.

Each CE device serves its own VPN and maintains only one set of forwarding mechanisms.

The PE devices connect to the public network and the VPNs. Each PE device must strictly

distinguish the information for different networks, and maintain a separate forwarding mechanism for each network. On a PE device, a set of software and hardware that serve the same network forms an instance. Multiple instances can exist on the same PE device, and an instance can reside on different PE devices. On a PE device, the instance for the public network is called the public network instance, and those for VPNs are called VPN instances.

Multicast application in VPNs

•

A PE device that supports multicast for VPNs does the following operations:

Maintains an independent set of multicast forwarding mechanisms for each VPN, including the

multicast protocols, PIM neighbor information, and multicast routing table. In a VPN, the device forwards multicast data based on the forwarding table or routing table for that VPN.

Implements the isolation between different VPNs. Implements information exchange and data conversion between the public network and VPN

instances.

For example, as shown in Figure 8, a multicast source in VPN A sends multicast data to a multicast group. Only receivers t hat belong t o both t he multicas t group and VPN A can receive the m ulticast data. The multicast data is multicast both in VPN A and on the public network.

Configuring IGMP snooping

Multicast packet transmission

without IGMP snooping

Source

Multicast router

Host A

Receiver

Host B

Host C

Receiver

Multicast packets

Layer 2

switch

Multicast packet transmission

when IGMP

snooping runs

Source

Multicast router

Host A

Receiver

Host B

Host C

Receiver

Layer 2 switch

Overview

IGMP snooping runs on a Layer 2 device as a multicast constraining mechanism to improve multicast forwarding efficiency. It creates La yer 2 multicast forwarding e ntries from IGMP packets that are exchanged between the hosts and the router.

As shown in Figure 9, when IGMP snooping is not enabled, the Layer 2 switch floods multicast packets to all hosts in a VLAN or VSI. When IGMP snooping is enabled, the Layer 2 switch forwards multicast packets of known multicast groups to only the receivers.

Figure 9 Multicast packet transmission without and with IGMP snooping

IGMP snooping ports

As shown in Figure 10, IGMP snooping runs on Switch A and Switch B, and Host A and Host C are receivers in a multicast group. IGMP snooping ports are divided into member ports and router ports.

Figure 10 IGMP snooping ports

•

Router A Switch A

Switch B

GE1/0/1 GE1/0/2

GE1/0/3

GE1

/0/2

Receiver

Host A

Host B

Host C

Host D

Source

Multicast packets

Router port

Member port

Router ports

On an IGMP snooping La yer 2 d evice, t he por ts to ward La yer 3 m ulticast d evices are c alled r outer ports. In Figure 10, GigabitEth ernet 1/0/1 of Switch A and GigabitEthernet 1/0/1 of Switc h B are router ports.

Router ports contain the following types:

Dynamic router port—When a port receives an IGMP general query whose source address is

not 0.0.0.0 or receives a PIM hello message, the port is added into the dynamic router port list. At the same time, an aging timer is started for the port. If the port receives either of the messages before the timer expires, the timer is reset. If the port does not receive either of the messages when the timer expires, the port is removed from the dynamic router port list.

Static router port—When a port is statically configured as a router port, it is added into the

static router port list. The static router port does not age out, and it can be deleted only manually.

Do not confuse th e "router port" i n IGMP snoop ing wit h the "rout ed inter face" co mmonl y known as the "Layer 3 interface." The router port in IGMP snooping is a Layer 2 interface.

Member ports

On an IGMP snooping Layer 2 device, the ports tow ard rece iver h osts are c alled m em ber ports . In

Figure 10, GigabitEthernet 1/0/2 and GigabitEthernet 1/0/3 of Switch A and GigabitEthernet 1/0/2 of

Switch B are member ports. Member ports contain the following types:

Dynamic member port—When a port receives an IGMP report, it is added to the associated

dynamic IGMP snooping forwarding entry as an outgoing interface. At the same time, an aging timer is started for the port. If the port receives an IGMP report before the timer expires, the timer is reset. If the port does not receive an IGMP report when the timer expires, the port is removed from the associated dynamic forwarding entry.

Static member port—When a port is statically configured as a member port, it is added to the

associated static IGMP snooping forwarding entry as an outgoing interface. The static member port does not age out, and it can be deleted only manually.

Unless otherwise spec if ied, router ports and member ports in this document include both static and dynamic router ports and member ports.

How IGMP snooping works

•

The ports in this section are dynamic ports. For information about how to configure and remove static ports, see "Configuring static ports."

IGMP messages types include general query, IGMP report, and leave message. An IGMP snooping-enabled Layer 2 device performs differently depending on the message types.

General query

The IG MP querier periodically sends IGM P general queries to all hosts and routers on th e local subnet to check for the existence of multicast group members.

After receiving an IGMP general query , the Layer 2 device forwards the query to all ports in the VLAN or VSI except the receiving port. The Layer 2 device also performs one of the following actions:

If the receiving port is a dynamic router port in the dynamic router port list, the Layer 2 device

restarts the aging timer for the port.

If the receiving port does not exist in the dynamic router port list, the Layer 2 device adds the

port to the dynamic router port list. It also starts an aging timer for the port.

IGMP report

A host sends an IGMP report to the IGMP querier for the following purposes:

Responds to queries if the host is a multicast group member. Applies for a multicast group membership.

After receiving an IGM P report from a host, the L ayer 2 device forw ards the report throu gh all the router ports in the VL AN or VSI. It also resol ves the address of the r eported multicast gr oup, and looks up the forwarding table for a matching entry as follows:

If no match is found, the Layer 2 device creates a forwarding entry with the receiving port as an

outgoing interface. It also marks the receiving port as a dynamic member port and starts an aging timer for the port.

If a match is found but the matching forwarding entry does not contain the receiving port, the

Layer 2 device adds the receiving port to the outgoing interface list. It also marks the receiving port as a dynamic member port and starts an aging timer for the port.

If a match is found and the matching forwarding entry contains the receiving port, the Layer 2

device restarts the aging timer for the port.

In an application with a group policy configured on an IGMP snooping-enabled Layer 2 device, when a user requests a m ulticast program, the us er's host initiates an IG MP report. After receiving this report, the Layer 2 device resolves the multicast group address in the rep ort and performs ACL filtering on the report. If the report passes ACL filtering, the Layer 2 device creates an IGMP snooping forwarding entry for the multicast group with the receiving port as an outgoing interface. If the report does not pass ACL filtering, the Layer 2 device drops this report. The multicast data for the multicast group is not sent to this port, and the user cannot re trie ve the progr am.

A Layer 2 device does not forward an IGMP report thr ough a non-router p ort because of the host IGMP report suppression mechanism. For more information about the IGMP report suppression mechanism, see "Configuring IGMP."

Leave message

An IGMPv1 receiver host does not send any leave messages when it leaves a multicast group. The Layer 2 device cannot imm ediate ly update the s tatus of the por t that conn ects to the rec eiver host. The Layer 2 device does not remove the port from the outgoing interface list in the associated forwarding entry until the aging time for the group expires.

An IGMPv2 or IGMPv3 host sends an IGMP leave message when it leaves a multicast group. When the Layer 2 device receives an IGMP leave message on a dynamic member port, the Layer 2

device first examines whether a forwarding entry matches the group address in the message.

•

Host A

Receiver

Host B

Host C

Receiver

IGMP Querier

Router A

Proxy

Switch A

Query from Router A Report from Switch A Query from Switch A Report from Host

IP network

If no match is found, the Layer 2 device discards the IGMP leave message. If a match is found but the receiving port is not an outgoing interface in the forwarding entry , the

Layer 2 device discards the IGMP leave message.

If a match is found and the receiving port is not the only outgoing interface in the forwarding

entry, the Layer 2 device performs the following actions:

 Discards the IGMP leave message.  Sends an IGMP group-specific query to identify whether the group has active receivers

attached to the receiving port.

 Sets the aging timer for the receiving port to twice the IGMP last member query interval.

If a match is found and the receiving port is the only outgoing interface in the forwarding entry,

the Layer 2 device performs the following actions:

 Forwards the IGMP leave message to all router ports in the VLAN or VSI.  Sends an IGMP group-specific query to identify whether the group has active receivers

attached to the receiving port.

 Sets the aging timer for the receiving port to twice the IGMP last member query interval.

After receiving the IGMP leave mes sage on a port, the IGMP querier resol ves the multicast group address in the message. Then, it sends an IGMP group-specific query to the multicast group through the receiving port.

After receiving the IGM P group-specific query, the Layer 2 device f orwards the query through all router ports and mem ber ports of the group in the VLAN or V SI. Then, it waits for the respon ding IGMP report from the directly connected hosts. For the dynamic member port that received the leave message, the Layer 2 device also performs one of the following actions:

If the port receives an IGMP report before the aging timer expires, the Layer 2 device resets the

aging timer.

If the port does not receive an IGMP report when the aging timer expires, the Layer 2 device

removes the port from the forwarding entry for the multicast group.

IGMP snooping proxying

As shown in Figure 11, to reduce the number of IGMP reports and leave messages received by the upstream device, you can enable IGM P snooping prox ying on the edge device . The edge device then acts as a host to send IGMP reports and leave messages to Router A.

An edge device enabled with IGMP snooping proxying does not support the host IGMP report suppression mechanism. For more information about the IGMP report suppression mechanism, see "Configuring IGMP."

Figure 11 IGMP snooping proxying

•

The IGMP snooping proxy device processes different IGMP messages as follows:

General query.

After receiving an IGMP general query, the device forwards the query to all ports in the VLAN except the receiving port. The device also generates an IGMP report based on the local membership information and sends the report to all router ports.

Group-specific query or group-and-source-specific query.

After receiving an IGMP group-specific query or group-and-source-specific query, the device forwards the query to all router ports in the VLAN except the receiving port. If the forwarding entry has a member port, the device sends a report to all router ports in the VLAN.

Report.

After receiving an IGMP report from a host, the devic e looks up the forwarding table for a matching entry as follows:

 If a match is found and the matching forwarding entry contains the receiving port, the device

resets the aging timer for the port.

 If a match is found but the matching forwarding entry does not contain the receiving port, the

device adds the receiving port to the outg oin g interface list. It also marks the receiving port as a dynamic member port and starts an aging timer for the port.

 If no match is found, the device creates a forwarding entry with the receiving port as an

outgoing interface. It also marks the receiving port as a dynamic member port and starts an aging timer for the port. Then it sends the report to all router ports.

Leave message.

After receiving an IGMP leave message on a port, the device sends an IGMP group-specific query through the receiving port. The device sends the IGMP leave message to all router ports only when the last member port is removed from the forwarding entry.

Protocols and standards

RFC 4541, Considerat ions for Internet G ro up Man agement Protoc ol ( IG MP) and Multicast Lis tener Discovery (MLD) Snooping Switches

Configuration restrictions and guidelines

When you configure IGMP snooping, follow these restrictions and guidelines:

If you change the VPN instance bound to the VLAN interface of a VLAN, Layer 2 multicast traffic

in the VLAN is interrupted. To allow new IGMP snooping forwarding entries to be created, execute the reset igmp-snooping group command.

For IGMP reports received from secondary VLANs, the relevant IGMP snooping forwarding

entries are maintained by the primary VLAN. Therefore, you need to enable IGMP snooping only for the primary VLAN. The IGMP snooping configuration made in secondary VLANs does not take effect. For more information about primary VLANs and secondary VLANs, see Layer 2—LAN Switching Configuration Guide.

The IGMP snooping configurations made on Layer 2 aggregate interfaces do not interfere with

the configurations made on member ports. In addition, the configurations made on Layer 2 aggregate interfaces do not take part in aggregation calculations. The configuration made on a member port of the aggregate group takes effect after the port leaves the aggregate group.

IGMP snooping configuration task list

You can configure IGMP snooping for VLANs or VSIs.

IGMP snooping configuration t as k list for VLANs

Tasks at a glance

Configuring basic IGMP snooping features:

• (Required.) Enabling IGMP snooping

• (Optional.) Specifying an IGMP snooping version

• (Optional.) Setting the maximum number of IGMP snooping forwarding entries

• (Optional.) Configuring static multicast MAC address entries

• (Optional.) Setting the IGMP last member query interval

Configuring IGMP snooping port features:

• (Optional.) Setting aging timers for dynamic ports

• (Optional.) Configuring static ports

• (Optional.) Configuring a port as a simulated member host

• (Optional.) Enabling fast-leave processing

• (Optional.) Disabling a port from becoming a dynamic router port

Configuring the IGMP snooping querier:

• (Optional.) Enabling the IGMP snooping querier

• (Optional.) Configuring parameters for IGMP general queries and responses

(Optional.) Enabling IGMP snooping proxying

Configuring parameters for IGMP messages:

• (Optional.) Configuring the source IP address for IGMP messages

• (Optional.) Setting the 802.1p priority for IGMP messages

Configuring IGMP snooping policies:

• (Optional.) Configuring a multi cast group policy

• (Optional.) Enabling multicast source port filtering

• (Optional.) Enabling dropp ing unknown multicast data

• (Optional.) Enabling IGMP report suppression

• (Optional.) Setting the maximum number of multicast groups on a port

• (Optional.) Enabling mul tic ast group r epl ace men t

• (Optional.) Enabling host tracking

IGMP configuration task list for VSIs

Configuring basic IGMP snooping features:

• (Required.) Enabling IGMP snooping

• (Optional.) Specifying an IGMP snooping version

• (Optional.) Setting the maximum number of IGMP snooping forwarding entries

• (Optional.) Setting the IGMP last member query interval

Configuring IGMP snooping port features:

• (Optional.) Setting aging timers for dynamic ports

Configuring the IGMP snooping querier:

• (Optional.) Enabling the IGMP snooping querier

• (Optional.) Configuring parameters for IGMP general queries and responses

Configuring parameters for IGMP messages:

• (Optional.) Configuring the source IP address for IGMP messages

Tasks at a glance

• (Optional.) Setting the 802.1p priority for IGMP messages

Configuring IGMP snooping policies:

•

Step

Command

Remarks

Step

Command

Remarks

By default, IGMP snooping is

• (Optional.) Enabling dropp ing unknown multicast data

• (Optional.) Enabling mul tic ast group r epl ace men t

Configuring basic IGMP snooping features

Before you configure basic IGMP snooping features, complete the following tasks:

Configure VLANs or VSIs. Determine the IGMP snooping version. Determine the maximum number of IGMP snooping forwarding entries. Determine the IGMP last member query interval.

Enabling IGMP s nooping

When you enable IGMP snooping, follow these restrictions and guidelines:

You must enable IGMP snooping globally before you enable it for a VLAN or VSI. IGMP snooping configuration made in VLAN or VSI view takes effect only on the member ports

in that VLAN or VSI.

You can enable IGMP snooping for the specified VLANs in IGMP-snoopi ng vi e w, for a VSI in

VSI view, or for a VLAN in VLAN view. For a VLAN, the configuration in VLAN view has the same priority as the configuration in IGMP-snooping view, and the most recent configuration takes effect.

Enabling IGMP snooping in IGMP-snooping view

1. Enter system view.

2. Enable IGMP snooping

globally and enter IGMP-snooping view.

3. Enable IGMP snooping for the specified VLANs.

system-view

igmp-snooping

enable vlan

vlan-list

Enabling IGMP snooping in VLAN or VSI view

1. Enter system view.

2. Enable IGMP snooping

globally and enter IGMP-snooping view.

3. Return to system view.

4. Enter VLAN view or VSI

view.

system-view

igmp-snooping

quit

• Enter VLAN view: vlan vlan-id

• Enter VSI view:

vsi vsi-name

N/A By default, IGMP snooping is

globally disabled. By default, IGMP snooping is

disabled for a VLAN.

N/A By default, IGMP snooping is

globally disabled.

N/A

Enable IGMP snooping for

igmp-snooping enable

Step

Command

Remarks

the VLAN or VSI.

disabled in a VLAN or VSI.

•

Step

Command

Remarks

Step

Command

Remarks

Specifying an IGMP snooping version

Different IGMP snooping versions process different versions of IGMP messages.

IGMPv2 snooping processes IGMPv1 and IGMPv2 messages, but it floods IGMPv3 messages

in the VLAN instead of processing them.

IGMPv3 snooping processes IGMPv1, IGMPv2, and IGMPv3 messages.

If you change IGMPv3 snooping to IGMPv2 snooping, the device performs the following actions:

Clears all IGMP snooping forwarding entries that are dynamicall y added. Keeps static IGMPv3 snooping forwarding entries (*, G). Clears static IGMPv3 snooping forwarding entries (S, G), which will be restored when IGMP

snooping is switched back to IGMPv3 snooping. For more information about static IGMP snooping forwarding entries, see "Configuring static ports." Y ou can specify the version for the specified VLANs in IGMP-snooping view, for a VSI in VSI view, or

for a VLAN in VLAN v ie w. For a VLAN, the c onf igura ti on i n V LA N v ie w has t he same priority as the configuration in IGMP-snooping view, and the most recent configuration takes effect.

Specifying an IGMP snooping version in IGMP-snooping view

1. Enter system view.

2. Enable IGMP snooping

globally and enter IGMP-snooping view.

3. Specify an IGMP snooping version for the specified VLANs.

system-view

igmp-snooping

version

vlan-list

version-number

vlan

N/A

The default setting is 2.

Specifying an IGMP snooping version in VLAN or VSI view

1. Enter system view.

2. Enter VLAN view or VSI view.

3. Specify an IGMP snooping

version for the VLAN or VSI.

system-view

• Enter VLAN view:

vlan vlan-id

• Enter VSI view:

vsi vsi-name

igmp-snooping version

version-number

N/A

The default setting is 2.

Setting the maximum number of IGMP s noopi ng forwarding entries

You can modify the maximum number of IGMP snooping forwarding entries, including dynamic entries and static entr ies. W hen the number of forwardin g entries on the de vice reaches the upper limit, the device does not automatically remove any existing entries. To allow new entries to be created, remove some entries manually.

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HPP Enterprises FlexNetwork 7500 Configuration Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Multicast overview

Introduction to multicast

Information transmission techniques

Unicast

Broadcast

Multicast

Multicast features

Common notations in m ulticast

Multicast benefits and applications

Multicast benefits

Multicast applications

Multicast models

ASM model

SFM model

SSM model

Multicast architecture

Multicast addresses

IP multicast addresses

Ethernet multicast MAC addresses

Multicast protoc ol s

Layer 3 multicast protocols

Layer 2 multicast protocols

Multicast packet forwarding mechanism

Multicast support for VPNs

Introduction to VPN instances

Multicast application in VPNs

Configuring IGMP snooping

Overview

IGMP snooping ports

Router ports

Member ports

How IGMP snooping works

General query

IGMP report

Leave message

IGMP snooping proxying

Protocols and standards

Configuration restrictions and guidelines

IGMP snooping configuration task list

IGMP snooping configuration t as k list for VLANs

IGMP configuration task list for VSIs

Configuring basic IGMP snooping features

Enabling IGMP s nooping

Enabling IGMP snooping in IGMP-snooping view

Enabling IGMP snooping in VLAN or VSI view

Specifying an IGMP snooping version

Specifying an IGMP snooping version in IGMP-snooping view

Specifying an IGMP snooping version in VLAN or VSI view

Setting the maximum number of IGMP s noopi ng forwarding entries