HP A5500 SI Switch, A5500 EI Switch Configuration Manual

HP A5500 EI & A5500 SI Switch Series IP Multicast

Configuration Guide

Abstract

This document describes the software features for the HP A Series products and guides you through the software configuration procedures. These configuration guides also provide configuration examples to help you apply software features to different network scenarios.

This documentation is intended for network planners, field technical support and servicing engineers, and network administrators working with the HP A Series products.

Part number: 5998-1712 Software version: Release 2208 Document version: 5W100-20110530

Legal and notice information

No part of this documentation may be reproduced or transmitted in any form or by any means without prior written consent of Hewlett-Packard Development Company, L.P.

The information contained herein is subject to change without notice.

HEWLETT-PACKARD COMPANY MAKES NO WARRANTY OF ANY KIND WITH REGARD TO THIS MATERIAL, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Hewlett-Packard shall not be liable for errors contained herein or for incidental or consequential damages in connection with the furnishing, performance, or use of this material.

The only warranties for HP products and services are set forth in the express warranty statements accompanying such products and services. Nothing herein should be construed as constituting an additional warranty. HP shall not be liable for technical or editorial errors or omissions contained herein.

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

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

Comparison of information transmission techniques ···························································································· 1 Features of multicast ················································································································································· 3 Common notations in multicast ······························································································································· 4

Advantages and applications of multicast ············································································································· 4 Multicast models ································································································································································ 5 Multicast architecture ························································································································································ 5

Multicast addresses ·················································································································································· 6

Multicast protocols ··················································································································································· 9 Multicast packet forwarding mechanism ····················································································································· 11 Multi-instance multicast ·················································································································································· 12

Introduction to the multi-instance concept ··········································································································· 12

Multi-instance application in multicast ················································································································ 12

IGMP snooping configuration ··································································································································· 14

IGMP snooping overview ·············································································································································· 14

Principle of IGMP snooping ································································································································· 14

Basic concepts in IGMP snooping ······················································································································· 15

How IGMP snooping works ································································································································· 16

IGMP snooping proxying ····································································································································· 18

Protocols and standards ······································································································································· 19 IGMP snooping configuration task list ························································································································· 19 Configuring basic functions of IGMP snooping ·········································································································· 20

Configuration prerequisites ·································································································································· 20

Enabling IGMP snooping ····································································································································· 20

Configuring the version of IGMP snooping ········································································································ 21

Configuring static multicast MAC address entries ····························································································· 21 Configuring IGMP snooping port functions ················································································································· 22

Configuration prerequisites ·································································································································· 22

Configuring aging timers for dynamic ports ······································································································ 23

Configuring static ports ········································································································································ 23

Configuring simulated joining ······························································································································ 24

Configuring fast-leave processing ······················································································································· 25

Disabling a port from becoming a dynamic router port ··················································································· 26 Configuring IGMP snooping querier ··························································································································· 26

Configuration prerequisites ·································································································································· 26

Enabling IGMP snooping querier ························································································································ 27

Configuring IGMP queries and responses ·········································································································· 27

Configuring source IP address of IGMP queries ································································································ 28 Configuring IGMP snooping proxying ························································································································ 29

Configuration prerequisites ·································································································································· 29

Enabling IGMP snooping proxying ····················································································································· 29

Configuring a source IP address for the IGMP messages sent by the proxy ·················································· 29 Configuring an IGMP snooping policy ························································································································ 30

Configuration prerequisites ·································································································································· 30

Configuring a multicast group filter ····················································································································· 30

Configuring multicast source port filtering ·········································································································· 31

Configuring the function of dropping unknown multicast data ········································································ 31

Configuring IGMP report suppression ················································································································ 32

Configuring the maximum number of multicast groups that a port can join··················································· 32

iii

Configuring multicast group replacement ··········································································································· 33

Configuring 802.1p precedence for IGMP messages ······················································································ 34

Configuring a multicast user control policy ········································································································ 35 Displaying and maintaining IGMP snooping ·············································································································· 36 IGMP snooping configuration examples ····················································································································· 36

Group policy and simulated joining configuration example ············································································ 36

Static port configuration example ······················································································································· 39

IGMP snooping querier configuration example ································································································· 42

IGMP snooping proxying configuration example ······························································································ 44

Multicast source and user control policy configuration example ····································································· 47 Troubleshooting IGMP snooping configuration ·········································································································· 52

Layer 2 multicast forwarding cannot function ···································································································· 52

Configured multicast group policy fails to take effect ······················································································· 53 Appendix (available only on the A5500 EI) ··············································································································· 53

Processing of multicast protocol messages ········································································································· 53

Multicast VLAN configuration ··································································································································· 55

Multicast VLAN overview ·············································································································································· 55 Multicast VLAN configuration task list ························································································································· 57 Configuring sub-VLAN-based multicast VLAN ············································································································ 57

Configuration prerequisites ·································································································································· 57

Configuring sub-VLAN-based multicast VLAN ···································································································· 57 Configuring port-based multicast VLAN ······················································································································ 58

Configuration prerequisites ·································································································································· 58

Configuring user port attributes ··························································································································· 58

Configuring multicast VLAN ports ······················································································································· 59 Displaying and maintaining multicast VLAN ·············································································································· 60 Multicast VLAN configuration examples ····················································································································· 60

Sub-VLAN-based multicast VLAN configuration ································································································· 60

Port-based multicast VLAN configuration ············································································································ 63

Multicast routing and forwarding configuration (available only on the A5500 EI) ·············································· 67

Multicast routing and forwarding overview ················································································································ 67

Introduction to multicast routing and forwarding ······························································································· 67

RPF check mechanism ··········································································································································· 67

Multicast static routes ············································································································································ 69

Multicast traceroute ··············································································································································· 71 Configuration task list ···················································································································································· 72 Enabling IP multicast routing ········································································································································· 72 Configuring multicast routing and forwarding ············································································································ 73

Configuration prerequisites ·································································································································· 73

Configuring multicast static routes ······················································································································· 73

Configuring a multicast routing policy ················································································································ 74

Configuring a multicast forwarding range ········································································································· 75

Configuring the multicast forwarding table size ································································································ 75

Tracing a multicast path ······································································································································· 76 Displaying and maintaining multicast routing and forwarding ················································································ 77 Configuration examples ················································································································································ 78

Changing an RPF route ········································································································································· 78

Creating an RPF route ··········································································································································· 80 Troubleshooting multicast routing and forwarding ····································································································· 82

Multicast static route failure ·································································································································· 82

Multicast data fails to reach receivers ················································································································ 83

IGMP configuration (available only on the A5500 EI) ··························································································· 84

IGMP overview ······························································································································································· 84

IGMP versions ························································································································································ 84

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Introduction to IGMPv1 ········································································································································· 84

Enhancements in IGMPv2 ···································································································································· 86

Enhancements in IGMPv3 ···································································································································· 86

IGMP SSM mapping ············································································································································· 88

IGMP proxying ······················································································································································ 89

Multi-instance IGMP ·············································································································································· 90

Protocols and standards ······································································································································· 90 IGMP configuration task list ·········································································································································· 90 Configuring basic functions of IGMP ··························································································································· 91

Configuration prerequisites ·································································································································· 91

Enabling IGMP ······················································································································································ 91

Configuring IGMP versions ·································································································································· 92

Configuring static joining ····································································································································· 93

Configuring a multicast group filter ····················································································································· 93

Configuring the maximum number of multicast groups that an interface can join ········································ 94 Adjusting IGMP performance ······································································································································· 94

Configuration prerequisites ·································································································································· 94

Configuring IGMP message options ··················································································································· 95

Configuring IGMP query and response parameters ························································································· 96

Configuring IGMP fast-leave processing ············································································································ 98 Configuring IGMP SSM mapping ································································································································ 98

Configuration prerequisites ·································································································································· 98

Enabling SSM mapping········································································································································ 99

Configuring SSM mappings ································································································································· 99 Configuring IGMP proxying ········································································································································· 99

Configuration prerequisites ·································································································································· 99

Enabling IGMP proxying ···································································································································· 100

Configuring multicast forwarding on a downstream interface ······································································· 100 Displaying and maintaining IGMP ····························································································································· 101 IGMP configuration examples ···································································································································· 102

Basic IGMP functions configuration example ··································································································· 102

SSM mapping configuration example ·············································································································· 104

IGMP proxying configuration example ············································································································· 107 Troubleshooting IGMP ················································································································································· 109

No membership information on the receiver-side router ················································································· 109

Inconsistent memberships on routers on the same subnet ··············································································· 110

PIM configuration (available only on the A5500 EI) ··························································································· 111

PIM overview ································································································································································ 111

PIM-DM overview ················································································································································ 111

PIM-SM overview ················································································································································· 114

BIDIR-PIM overview ············································································································································· 120

Administrative scoping overview ······················································································································· 123

PIM-SSM overview ·············································································································································· 125

Relationships among PIM protocols ·················································································································· 126

Multi-instance PIM ··············································································································································· 127

Protocols and standards ····································································································································· 127 Configuring PIM-DM ···················································································································································· 128

PIM-DM configuration task list ··························································································································· 128

Configuration prerequisites ································································································································ 128

Enabling PIM-DM ················································································································································ 128

Enabling state-refresh capability ························································································································ 129

Configuring state-refresh parameters ················································································································ 130

Configuring PIM-DM graft retry period ············································································································· 130 Configuring PIM-SM ···················································································································································· 131

PIM-SM configuration task list ···························································································································· 131

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Configuration prerequisites ································································································································ 131

Enabling PIM-SM ················································································································································· 132

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

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

Configuring administrative scoping ·················································································································· 139

Configuring multicast source registration ········································································································· 141

Disabling SPT switchover ···································································································································· 142 Configuring BIDIR-PIM ················································································································································· 143

BIDIR-PIM configuration task list ························································································································· 143

Configuration prerequisites ································································································································ 143

Enabling PIM-SM ················································································································································· 144

Enabling BIDIR-PIM ·············································································································································· 145

Configuring an RP ··············································································································································· 145

Configuring a BSR ··············································································································································· 147

Configuring administrative scoping ·················································································································· 151 Configuring PIM-SSM ·················································································································································· 153

PIM-SSM configuration task list ·························································································································· 153

Configuration prerequisites ································································································································ 153

Enabling PIM-SM ················································································································································· 154

Configuring the SSM group range ···················································································································· 155 Configuring PIM common features ····························································································································· 155

PIM common feature configuration task list ······································································································ 155

Configuration prerequisites ································································································································ 156

Configuring a multicast data filter ····················································································································· 156

Configuring a hello message filter ···················································································································· 157

Configuring PIM hello options ··························································································································· 157

Configuring the prune delay ······························································································································ 159

Configuring PIM common timers ······················································································································· 159

Configuring join/prune message sizes ············································································································· 161 Displaying and maintaining PIM ································································································································ 161 PIM configuration examples ······································································································································· 162

PIM-DM configuration example ························································································································· 162

PIM-SM non-scoped zone configuration example ··························································································· 166

PIM-SM admin-scope zone configuration example ························································································· 171

BIDIR-PIM configuration example ······················································································································ 177

PIM-SSM configuration example ······················································································································· 182 Troubleshooting PIM configuration ···························································································································· 185

Failure of building a multicast distribution tree correctly ················································································ 185

Multicast data abnormally terminated on an intermediate router ·································································· 186

RPs unable to join SPT in PIM-SM ······················································································································ 187

RPT establishment failure or source registration failure in PIM-SM ································································ 187

MSDP configuration (available only on the A5500 EI) ························································································ 189

Introduction to MSDP ··················································································································································· 189

How MSDP works ··············································································································································· 189

Multi-instance MSDP ··········································································································································· 194

Protocols and standards ····································································································································· 195 MSDP configuration task list ······································································································································· 195 Configuring basic functions of MSDP ························································································································ 195

Configuration prerequisites ································································································································ 195

Enabling MSDP ···················································································································································· 196

Creating an MSDP peer connection ·················································································································· 196

Configuring a static RPF peer ···························································································································· 197 Configuring an MSDP peer connection ····················································································································· 197

Configuration prerequisites ································································································································ 197

Configuring MSDP peer description ················································································································· 197

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Configuring an MSDP mesh group ··················································································································· 198

Configuring MSDP peer connection control ····································································································· 198 Configuring SA messages related parameters ········································································································· 199

Configuration prerequisites ································································································································ 199

Configuring SA message content ······················································································································ 199

Configuring SA request messages ····················································································································· 200

Configuring SA message filtering rules ············································································································· 200

Configuring the SA cache mechanism ·············································································································· 201 Displaying and maintaining MSDP ···························································································································· 202 MSDP configuration examples ··································································································································· 202

Inter-AS multicast configuration leveraging BGP routes ·················································································· 202

Inter-AS multicast configuration leveraging static RPF peers ·········································································· 208

Anycast RP configuration ···································································································································· 211

SA message filtering configuration ··················································································································· 215 Troubleshooting MSDP ················································································································································ 218

MSDP peers stay in down state ························································································································· 218

No SA entries in the switch’s SA cache ············································································································ 219

Inter-RP communication faults in Anycast RP application ················································································ 219

MBGP configuration (available only on the A5500 EI) ······················································································· 220

MBGP overview ··························································································································································· 220 Protocols and standards ·············································································································································· 220 MBGP configuration task list ······································································································································· 220 Configuring MBGP basic functions ···························································································································· 221

Configuration prerequisites ································································································································ 221

Configuration procedure ···································································································································· 221 Controlling route advertisement and reception ········································································································· 222

Configuration prerequisites ································································································································ 222

Configuring MBGP route redistribution ············································································································· 222

Configure default route redistribution into MBGP ···························································································· 222

Configuring MBGP route summarization ·········································································································· 223

Advertising a default route to an IPv4 MBGP peer or peer group ································································ 224

Configuring outbound MBGP route filtering ····································································································· 224

Configuring inbound MBGP route filtering ······································································································· 225

Configuring MBGP route dampening ··············································································································· 226 Configuring MBGP route attributes ···························································································································· 226

Configuration prerequisites ································································································································ 226

Configuring MBGP route preferences ··············································································································· 226

Configuring the default local preference ·········································································································· 227

Configuring the MED attribute ··························································································································· 227

Configuring the Next Hop attribute ··················································································································· 228

Configuring the AS-PATH attribute ···················································································································· 228 Tuning and optimizing MBGP networks ···················································································································· 229

Configuration prerequisites ································································································································ 229

Configuring MBGP soft reset······························································································································ 229

Enabling the MBGP ORF capability ·················································································································· 230

Configuring the maximum number of MBGP routes for load balancing ······················································· 231 Configuring a large scale MBGP network ················································································································ 232

Configuration prerequisites ································································································································ 232

Configuring IPv4 MBGP peer groups ··············································································································· 232

Configuring MBGP community ·························································································································· 232

Configuring an MBGP route reflector ··············································································································· 233 Displaying and maintaining MBGP ··························································································································· 234

Displaying MBGP ················································································································································ 234

Resetting MBGP connections ······························································································································ 235

Clearing MBGP information ······························································································································· 235

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MBGP configuration example ···································································································································· 236

MLD snooping configuration ·································································································································· 240

MLD snooping overview ·············································································································································· 240

Introduction to MLD snooping ···························································································································· 240

Basic concepts in MLD snooping ······················································································································· 241

How MLD snooping works ································································································································· 242

MLD snooping proxying ····································································································································· 244

Protocols and standards ····································································································································· 245 MLD snooping configuration task list ························································································································· 245 Configuring basic functions of MLD snooping ·········································································································· 246

Configuration prerequisites ································································································································ 246

Enabling MLD snooping ····································································································································· 246

Configuring the version of MLD snooping ········································································································ 247

Configuring IPv6 static multicast MAC address entries··················································································· 247 Configuring MLD snooping port functions ················································································································· 248

Configuration prerequisites ································································································································ 248

Configuring aging timers for dynamic ports ···································································································· 248

Configuring static ports ······································································································································ 249

Configuring simulated joining ···························································································································· 250

Configuring fast-leave processing ····················································································································· 250

Disabling a port from becoming a dynamic router port ················································································· 251 Configuring MLD snooping querier ··························································································································· 252

Configuration prerequisites ································································································································ 252

Enabling MLD snooping querier ························································································································ 252

Configuring MLD queries and responses ·········································································································· 253

Configuring source IPv6 addresses of MLD queries ························································································ 254 Configuring MLD snooping proxying ························································································································ 254

Configuration prerequisites ································································································································ 254

Enabling MLD snooping proxying ····················································································································· 254

Configuring a source IPv6 address for the MLD messages sent by the proxy ·············································· 255 Configuring an MLD snooping policy ························································································································ 255

Configuration prerequisites ································································································································ 255

Configuring an IPv6 multicast group filter ········································································································ 255

Configuring IPv6 multicast source port filtering ······························································································· 256

Configuring the function of dropping unknown IPv6 multicast data ······························································ 257

Configuring MLD report suppression ················································································································ 257

Configuring the maximum number of multicast groups that a port can join················································· 258

Configuring IPv6 multicast group replacement ································································································ 258

Configuring 802.1p precedence for MLD messages ······················································································ 259

Configuring an IPv6 multicast user control policy ···························································································· 260 Displaying and maintaining MLD snooping ·············································································································· 261 MLD snooping configuration examples ····················································································································· 262

IPv6 group policy and simulated joining configuration example ·································································· 262

Static port configuration example ····················································································································· 264

MLD snooping querier configuration example ································································································· 268

MLD snooping proxying configuration example ······························································································ 269

IPv6 multicast source and user control policy configuration example ··························································· 272 Troubleshooting MLD snooping ·································································································································· 277

Layer 2 multicast forwarding cannot function ·································································································· 277

Configured IPv6 multicast group policy fails to take effect ············································································· 278 Appendix (available only on the A5500 EI) ············································································································· 278

Processing of IPv6 multicast protocol messages······························································································· 278

IPv6 multicast VLAN configuration ························································································································· 280

IPv6 multicast VLAN overview ···································································································································· 280 IPv6 multicast VLAN configuration task list ··············································································································· 282

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Configuring IPv6 sub-VLAN-based IPv6 multicast VLAN ························································································· 282

Configuration prerequisites ································································································································ 282

Configuring sub-VLAN-based IPv6 multicast VLAN ························································································· 282 Configuring port-based IPv6 multicast VLAN ············································································································ 283

Configuration prerequisites ································································································································ 283

Configuring user port attributes ························································································································· 283

Configuring IPv6 multicast VLAN ports ············································································································· 284 Displaying and maintaining IPv6 multicast VLAN ···································································································· 285 IPv6 multicast VLAN configuration examples ············································································································ 285

Sub-VLAN-based multicast VLAN configuration example ··············································································· 285

Port-based multicast VLAN configuration example ·························································································· 288

IPv6 multicast routing and forwarding configuration (available only on the A5500 EI) ··································· 292

IPv6 multicast routing and forwarding overview ······································································································ 292

RPF check mechanism ········································································································································· 292 Configuration task list ·················································································································································· 294 Enabling IPv6 multicast routing ·································································································································· 295 Configuring IPv6 multicast routing and forwarding ································································································· 295

Configuration prerequisites ································································································································ 295

Configuring an IPv6 multicast routing policy ··································································································· 295

Configuring an IPv6 multicast forwarding range ····························································································· 296

Configuring the IPv6 multicast forwarding table size ······················································································ 296 Displaying and maintaining IPv6 multicast routing and forwarding ······································································ 297 Troubleshooting IPv6 multicast policy configuration ································································································ 298

Abnormal termination of IPv6 multicast data ··································································································· 298

MLD configuration (available only on the A5500 EI) ·························································································· 300

MLD overview ······························································································································································· 300

MLD versions ························································································································································ 300

How MLDv1 works ·············································································································································· 300

How MLDv2 works ·············································································································································· 302

MLD Messages ···················································································································································· 303

MLD SSM mapping ············································································································································· 306

MLD proxying ······················································································································································ 307

Protocols and standards ····································································································································· 307 MLD configuration task list ·········································································································································· 308 Configuring basic functions of MLD ··························································································································· 308

Configuration prerequisites ································································································································ 308

Enabling MLD ······················································································································································ 309

Configuring the MLD version ····························································································································· 309

Configuring static joining ··································································································································· 310

Configuring an ipv6 multicast group filter ········································································································ 310

Configuring the maximum number of IPv6 multicast groups that an interface can join ······························ 311 Adjusting MLD performance ······································································································································· 311

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

Configuring MLD message options ··················································································································· 312

Configuring MLD query and response parameters ························································································· 313

Configuring MLD fast leave processing ············································································································ 315 Configuring MLD SSM mapping ································································································································ 315

Configuration prerequisites ································································································································ 315

Enabling MLD SSM mapping ····························································································································· 315

Configuring MLD SSM mappings ······················································································································ 316 Configuring MLD proxying ········································································································································· 316

Configuration prerequisites ································································································································ 316

Enabling MLD proxying ······································································································································ 316

Configuring IPv6 multicast forwarding on a downstream interface ······························································ 317 Displaying and maintaining MLD configuration ······································································································· 318

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MLD configuration examples ······································································································································ 319

Basic MLD functions configuration example ····································································································· 319

MLD SSM mapping configuration example ····································································································· 321

MLD proxying configuration example ··············································································································· 324 Troubleshooting MLD ··················································································································································· 325

No member information on the receiver-side router ························································································ 325

Inconsistent memberships on routers on the same subnet ··············································································· 326

IPv6 PIM configuration (available only on the A5500 EI) ··················································································· 327

IPv6 PIM overview ························································································································································ 327

IPv6 PIM-DM overview ········································································································································ 327

IPv6 PIM-SM overview ········································································································································ 330

IPv6 BIDIR-PIM overview ····································································································································· 336

IPv6 administrative scoping overview ··············································································································· 340

IPv6 PIM-SSM overview ······································································································································ 342

Relationships among IPv6 PIM protocols ·········································································································· 344

Protocols and standards ····································································································································· 344 Configuring IPv6 PIM-DM ············································································································································ 345

IPv6 PIM-DM configuration task list ··················································································································· 345

Configuration prerequisites ································································································································ 345

Enabling IPv6 PIM-DM ········································································································································ 345

Enabling state-refresh capability ························································································································ 346

Configuring state refresh parameters ················································································································ 346

Configuring IPv6 PIM-DM graft retry period ···································································································· 347 Configuring IPv6 PIM-SM ············································································································································ 347

IPv6 PIM-SM configuration task list ··················································································································· 347

Configuration prerequisites ································································································································ 348

Enabling IPv6 PIM-SM········································································································································· 348

Configuring an RP ··············································································································································· 349

Configuring a BSR ··············································································································································· 351

Configuring IPv6 administrative scoping ·········································································································· 355

Configuring IPv6 multicast source registration ································································································· 356

Disabling SPT switchover ···································································································································· 357 Configuring IPv6 BIDIR-PIM ········································································································································· 358

IPv6 BIDIR-PIM configuration task list ················································································································ 358

Configuration prerequisites ································································································································ 358

Enabling IPv6 PIM-SM········································································································································· 359

Enabling IPv6 BIDIR-PIM ····································································································································· 359

Configuring an RP ··············································································································································· 359

Configuring a BSR ··············································································································································· 362

Configuring IPv6 administrative scoping ·········································································································· 365 Configuring IPv6 PIM-SSM ·········································································································································· 367

IPv6 PIM-SSM configuration task list ················································································································· 367

Configuration prerequisites ································································································································ 367

Enabling IPv6 PIM-SM········································································································································· 367

Configuring the IPv6 SSM group range ··········································································································· 368 Configuring IPv6 PIM common features ···················································································································· 368

IPv6 PIM common feature configuration task list ····························································································· 369

Configuration prerequisites ································································································································ 369

Configuring an IPv6 multicast data filter ·········································································································· 369

Configuring a hello message filter ···················································································································· 370

Configuring IPv6 PIM hello options ··················································································································· 370

Configuring the prune delay ······························································································································ 372

Configuring IPv6 PIM common timers ··············································································································· 372

Configuring join/prune message sizes ············································································································· 374 Displaying and maintaining IPv6 PIM ······················································································································· 374

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IPv6 PIM configuration examples ······························································································································· 375

IPv6 PIM-DM configuration example ················································································································· 375

IPv6 PIM-SM non-scoped zone configuration example ··················································································· 379

IPv6 PIM-SM admin-scope zone configuration example ················································································· 384

IPv6 BIDIR-PIM configuration example ·············································································································· 396

IPv6 PIM-SSM configuration example ··············································································································· 400 Troubleshooting IPv6 PIM configuration ···················································································································· 403

Failure to build a multicast distribution tree correctly ······················································································ 403

IPv6 multicast data abnormally terminated on an intermediate router ·························································· 404

RPs unable to join SPT in IPv6 PIM-SM ············································································································· 404

RPT establishment failure or source registration failure in IPv6 PIM-SM ························································ 405

IPv6 MBGP configuration (available only on the A5500 EI) ··············································································· 406

IPv6 MBGP overview ··················································································································································· 406 IPv6 MBGP configuration task list ······························································································································ 406 Configuring IPv6 MBGP basic functions ···················································································································· 407

Configuration prerequisites ································································································································ 407

Configuring an IPv6 MBGP peer ······················································································································· 407

Configuring a preferred value for routes from a peer/peer group ······························································· 408 Controlling route distribution and reception ············································································································· 408

Configuration prerequisites ································································································································ 408

Injecting a local IPv6 MBGP route ····················································································································· 408

Configuring IPv6 MBGP route redistribution ···································································································· 409

Configuring IPv6 MBGP route summarization ································································································· 409

Advertising a default route to a peer or peer group ······················································································· 409

Configuring outbound IPv6 MBGP route filtering ···························································································· 410

Configuring inbound IPv6 MBGP route filtering ······························································································ 411

Configuring IPv6 MBGP route dampening ······································································································· 411 Configuring IPv6 MBGP route attributes ···················································································································· 412

Configuration prerequisites ································································································································ 412

Configuring IPv6 MBGP route preferences ······································································································ 412

Configuring the default local preference ·········································································································· 412

Configuring the MED attribute ··························································································································· 413

Configuring the NEXT_HOP attribute ················································································································ 413

Configuring the AS_PATH attribute ··················································································································· 414 Tuning and optimizing IPv6 MBGP networks············································································································ 414

Configuration prerequisites ································································································································ 414

Configuring IPv6 MBGP soft reset ····················································································································· 414

Enabling the IPv6 MBGP ORF capability ········································································································· 415

Configuring the maximum number of equal-cost routes for load-balancing ················································· 417 Configuring a large scale IPv6 MBGP network ········································································································ 417

Configuration prerequisites ································································································································ 417

Configuring an IPv6 MBGP peer group ··········································································································· 417

Configuring IPv6 MBGP community ·················································································································· 418

Configuring an IPv6 MBGP route reflector ······································································································· 418 Displaying and maintaining IPv6 MBGP ··················································································································· 419

Displaying IPv6 MBGP ······································································································································· 419

Resetting IPv6 MBGP connections ····················································································································· 420

Clearing IPv6 MBGP information ······················································································································ 421 IPv6 MBGP configuration example ···························································································································· 421

Support and other resources ·································································································································· 424

Contacting HP ······························································································································································ 424

Subscription service ············································································································································ 424 Related information ······················································································································································ 424

Documents ···························································································································································· 424

Websites ······························································································································································ 424

xi

Conventions ·································································································································································· 425

Index ········································································································································································ 427

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Multicast overview

NOTE:

This document focuses on the IP multicast technology and device operations. Unless otherwise stated, the term

multicast

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 new value-added services, such as live webcasting, web TV, distance learning, telemedicine, web radio, realtime video conferencing, and other bandwidth-critical and time-critical information services.

Comparison of information transmission techniques

in this document refers to IP multicast.

Unicast

In unicast transmission, the information source must send a separate copy of information to each host that needs the information.

Figure 1 Unicast transmission

Host A

Receiver

Host B

Source

Host C

Receiver

Host D

IP network

Packets for Host B

Packets for Host D

Packets for Host E

Receiver

Host E

In Figure 1, assume that 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.

1

Broadcast

In unicast transmission, the traffic transmitted over the network is proportional to the number of hosts that need the information. If a large number of hosts need the information, the information source must send a copy of the same information to each of these hosts. Sending many copies can place a tremendous pressure on the information source and the network bandwidth.

Unicast is not suitable for batch transmission of information.

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, assume that 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 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.

Unicast and broadcast techniques cannot provide point-to-multipoint data transmissions with the minimum network consumption.

Multicast transmission can solve this problem. When some hosts on the network need multicast information, the information sender, or multicast source, sends only one copy of the information. Multicast distribution trees are built through multicast routing protocols, and the information is replicated only on nodes where the trees branch.

2

Figure 3 Multicast transmission

The multicast source sends only one copy of the information to a multicast group. In Figure 3, Host B, Host D, and Host E, which are receivers of the information, 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: Because multicast traffic flows to the farthest-possible node from the

source before it is replicated and distributed, an increase in the number of hosts does not increase the load of the source or remarkably add to the usage of network resources.

• Advantages over broadcast: Because multicast data is sent only to the receivers that need it,

multicast uses network bandwidth reasonably and enhances network security. In addition, data broadcast is confined to the same subnet, but multicast is not.

Features of multicast

Multicast transmission has the following features:

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

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

• An information sender is called a “multicast source.” A multicast source can send data to multiple

multicast groups at the same time, and multiple multicast sources can send data to the same multicast group at the same time.

• All hosts that have joined a multicast group become members of the multicast group. The group

memberships are dynamic. Hosts can join or leave multicast groups at any time. Multicast groups are not subject to geographic restrictions.

• Routers or Layer 3 switches that support Layer 3 multicast are called “multicast routers” or “Layer 3

multicast devices.” In addition to providing the multicast routing function, a multicast router can

3

manage multicast group memberships on stub subnets with attached group members. A multicast router itself can be a multicast group member.

For a better understanding of the multicast concept, you can compare multicast transmission to the transmission of TV programs.

Table 1 An analogy between TV transmission and multicast transmission

TV 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 via the channel.

The user turns off the TV set or tunes to another channel.

Common notations in multicast

The following notations are commonly used in multicast transmission:

• (*, G)—Indicates a rendezvous point tree (RPT), or a multicast packet that any multicast source

sends to multicast group G. Here, the asterisk represents any multicast source, and “G” represents a specific multicast group.

• (S, G)—Indicates a shortest path tree (SPT), or a multicast packet that multicast source S sends to

multicast group G. Here, “S” represents a specific multicast source, and “G” represents a specific multicast group.

NOTE:

A multicast source sends multicast data to a multicast group.

The receiver starts to receive the multicast data that the source is sending to the multicast group.

The receiver leaves the multicast group or joins another group.

For more information about the concepts RPT and SPT, see the chapters “PIM configuration” PIM configuration.”

Advantages and applications of multicast

Advantages of multicast

The multicast technique has the following advantages:

• 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.

Applications of multicast

The multicast technique has the following applications:

• Multimedia and streaming applications, such as web TV, web radio, and realtime video/audio

conferencing

4

and “IPv6

• Communication for training and cooperative operations, such as distance learning and

telemedicine

• Data warehouse and financial applications, such as stock quotes

• Any other point-to-multipoint applications for data distribution

Multicast models

Based on how the receivers treat the multicast sources, the multicast models include any-source multicast (ASM), source-filtered multicast (SFM), and source-specific multicast (SSM).

ASM model

In the ASM model, any sender can send information to a multicast group as a multicast source, and numbers of receivers can join a multicast group (identified by a group address) and can obtain multicast information addressed to that multicast group. In this model, receivers do not determine the positions of the multicast sources in advance. However, they can join or leave the multicast group at any time.

SFM model

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

The SFM model functionally extends the ASM model. The upper-layer software checks the source address of received multicast packets and permits or denies multicast traffic from specific sources. Therefore, receivers can receive the multicast data from only part of the multicast sources. To a receiver, not all multicast sources are valid: they are filtered.

SSM model

Users might be interested in the multicast data from only certain multicast sources. The SSM model provides a transmission service that enables users to specify the multicast sources that they are interested in at the client side.

The main difference between the SSM model and the ASM model is that in the SSM model, receivers have already determined the locations of the multicast sources by some other means. In addition, the SSM model uses a multicast address range that is different from that of the ASM/SFM model, and dedicated multicast forwarding paths are established between receivers and the specified multicast sources.

Multicast architecture

IP multicast addresses the following questions:

• 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 should information be transmitted to the receivers? (multicast routing)

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

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

multicast address.

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

is the basis for management of group memberships.

5

3. 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.

4. 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

Network-layer multicast addresses—namely, multicast IP addresses—enable communication between multicast sources and multicast group members. In addition, a technique must be available to map multicast IP addresses to link-layer multicast MAC addresses.

IP multicast addresses

1. IPv4 multicast addresses

Internet Assigned Numbers Authority (IANA) assigned the Class D address space—224.0.0.0 to

239.255.255.255—for IPv4 multicast.

Table 2 Class D IP address blocks and description

Address block Description

224.0.0.0 to 224.0.0.255

Reserved permanent group addresses. The IP address 224.0.0.0 is reserved. Other IP addresses can be used by routing protocols and for topology searching, protocol maintenance, and so on.

Table 3 lists common permanent group addresses. A packet

destined for an address in this block will not be forwarded beyond the local subnet regardless of the Time to Live (TTL) value in the IP header.

Globally scoped group addresses. This block includes the

224.0.1.0 to 238.255.255.255

following types of designated group addresses:

• 232.0.0.0/8—SSM group addresses

• 233.0.0.0/8—Glop group addresses

Administratively scoped multicast addresses. These addresses are

239.0.0.0 to 239.255.255.255

considered locally unique rather than globally unique, and can be reused in domains administered by different organizations without causing conflicts. For more information, see RFC 2365.

NOTE:

The membership of a group is dynamic. Hosts can join or leave multicast groups at any time.

“Glop” is a mechanism for assigning multicast addresses between different autonomous systems

(ASs). By filling an AS number into the middle two bytes of 233.0.0.0, you get 255 multicast addresses for that AS. For more information, see RFC 2770.

Table 3 Some reserved multicast addresses

Address Description

224.0.0.1 All systems on this subnet, including hosts and routers

224.0.0.2 All multicast routers on this subnet

224.0.0.3 Unassigned

6

Address Description

p

224.0.0.4 Distance Vector Multicast Routing Protocol (DVMRP) routers

224.0.0.5 Open Shortest Path First (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 Routing Information Protocol version 2 (RIPv2) routers

224.0.0.11 Mobile agents

224.0.0.12 Dynamic Host Configuration Protocol (DHCP) server/relay agent

224.0.0.13 All Protocol Independent Multicast (PIM) routers

224.0.0.14 Resource Reservation Protocol (RSVP) encapsulation

224.0.0.15 All Core-Based Tree (CBT) routers

224.0.0.16 Designated Subnetwork Bandwidth Management (SBM)

224.0.0.17 All SBMs

224.0.0.18 Virtual Router Redundancy Protocol (VRRP)

2. IPv6 multicast addresses

Figure 4 IPv6 multicast format

The following describes the fields of an IPv6 multicast address:

• 0xFF—The most significant eight bits are 11111111, which indicates that this address is an IPv6

multicast address.

• Flags—The Flags field contains four bits.

Figure 5 Format of the Flags field

Table 4 Description on the bits of the Flags field

Bit Descri

0 Reserved, set to 0

tion

• When set to 0, it indicates that this address is an IPv6 multicast address without an

R

embedded RP address.

• When set to 1, it indicates that this address is an IPv6 multicast address with an

embedded RP address—the P and T bits must also be set to 1.

7

Bit Description

g

• When set to 0, it indicates that this address is an IPv6 multicast address not based on

P

a unicast prefix.

• When set to 1, it indicates that this address is an IPv6 multicast address based on a

unicast prefix—the T bit must also be set to 1.

• When set to 0, it indicates that this address is an IPv6 multicast address permanently-

T

assigned by IANA.

• When set to 1, it indicates that this address is a transient, or dynamically assigned

IPv6 multicast address.

• Scope—The Scope field contains four bits, which indicate the scope of the IPv6 internetwork for

which the multicast traffic is intended.

Table 5 Values of the Scope field

Value Meanin

0, F Reserved

1 Interface-local scope

2 Link-local scope

3 Subnet-local scope

4 Admin-local scope

5 Site-local scope

6, 7, 9 through D Unassigned

8 Organization-local scope

E Global scope

• Group ID—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

When a unicast IP packet is transmitted over Ethernet, the destination MAC address is the MAC address of the receiver. When a multicast packet is transmitted over Ethernet, the destination address is a multicast MAC address because the packet is directed to a group formed by a number of receivers, rather than to one specific receiver.

1. 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 least-significant 23 bits are the least-significant 23 bits of a multicast IPv4 address.

8

Figure 6 IPv4-to-MAC address mapping

The most-significant four bits of a multicast IPv4 address are 1110, which indicates that this address is a multicast address. Only 23 bits of the remaining 28 bits are mapped to a MAC address, so five bits of the multicast IPv4 address are lost. As a result, 32 multicast IPv4 addresses map to the same IPv4 multicast MAC address. Therefore, in Layer 2 multicast forwarding, a switch might receive some multicast data destined for other IPv4 multicast groups. The upper layer must filter such redundant data.

2. IPv6 multicast MAC addresses

The most-significant 16 bits of an IPv6 multicast MAC address are 0x3333. The least-significant 32 bits are the least-significant 32 bits of a multicast IPv6 address.

Figure 7 An example of IPv6-to-MAC address mapping

Multicast protocols

NOTE:

Generally,

protocols are Layer 3 multicast protocols, which include IGMP, MLD, PIM, IPv6 PIM, MSDP, MBGP, and IPv6 MBGP. multicast protocols are Layer 2 multicast protocols, which include IGMP snooping, MLD snooping, multicast VLAN, and IPv6 multicast VLAN.

IGMP snooping, IGMP, multicast VLAN, PIM, MSDP, and MBGP are for IPv4. MLD snooping, MLD,

IPv6 multicast VLAN, IPv6 PIM, and IPv6 MBGP are for IPv6.

Layer 3 multicast

Layer 2 multicast refers to

refers to IP multicast working at the network layer. The related multicast

IP multicast working at the data link layer. The related

This section provides only general descriptions about applications and functions of the Layer 2 and

Layer 3 multicast protocols in a network. For more information about these protocols, see related chapters.

9

Layer 3 multicast protocols

Layer 3 multicast protocols include multicast group management protocols and multicast routing protocols.

Figure 8 Positions of Layer 3 multicast protocols

1. Multicast group management protocols

Typically, the Internet Group Management Protocol (IGMP) or Multicast Listener Discovery Protocol (MLD) is used between hosts and Layer 3 multicast devices that directly connect to the hosts. These protocols define the mechanism of establishing and maintaining group memberships between hosts and Layer 3 multicast devices.

2. Multicast routing protocols

A multicast routing protocol runs on Layer 3 multicast devices to establish and maintain multicast routes and forward multicast packets correctly and efficiently. Multicast routes constitute loop-free data transmission paths from a data source to multiple receivers, namely, a multicast distribution tree.

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, Protocol Independent Multicast (PIM) is most widely used. Based on the forwarding mechanism, PIM includes the dense mode—often called “PIM-DM”, and sparse mode—often called “PIM-SM.”

• An inter-domain multicast routing protocol delivers multicast information between two ASs. Mature

solutions include Multicast Source Discovery Protocol (MSDP) and Multicast Border Gateway Protocol (MBGP). MSDP propagates multicast source information among different ASs, and MBGP is an extension of the Multiprotocol Border Gateway Protocol (MP-BGP) for exchanging multicast routing information among different ASs.

For the SSM model, multicast routes are not divided into intra-domain routes and inter-domain routes. Because receivers know the positions of the multicast sources, channels established through PIM-SM are sufficient for the transport of multicast information.

Layer 2 multicast protocols

Layer 2 multicast protocols include IGMP snooping, MLD snooping, multicast VLAN, and IPv6 multicast VLAN.

10

Figure 9 Positions of Layer 2 multicast protocols

Source

Receiver Receiver

IPv4/IPv6 multicast packets

1. IGMP snooping and MLD snooping

Multicast VLAN

/IPv6 Multicast VLAN

IGMP Snooping /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, effectively controlling the flooding of multicast data in a Layer 2 network.

2. Multicast VLAN and IPv6 multicast VLAN

In the traditional multicast-on-demand mode, when users in different VLANs on a Layer 2 device need multicast information, the upstream Layer 3 device needs to forward a separate copy of the multicast data to each VLAN of the Layer 2 device. When the multicast VLAN or IPv6 multicast VLAN feature is enabled on the Layer 2 device, the Layer 3 multicast device sends only one copy of the multicast data to the multicast VLAN or IPv6 multicast VLAN on the Layer 2 device. This approach avoids waste of network bandwidth and extra burden on the Layer 3 device.

Multicast packet forwarding mechanism

In a multicast model, a multicast source sends information to the host group identified by the multicast group address in the destination address field of IP multicast packets. To deliver multicast packets to receivers located at different positions of the network, multicast routers on the forwarding paths usually need to forward multicast packets received on one incoming interface to multiple outgoing interfaces. Compared with a unicast model, a multicast model is more complex in the following aspects:

• To ensure multicast packet transmission in the network, unicast routing tables or multicast routing

tables—for example, MBGP routing table—specially provided for multicast must be used as guidance for multicast forwarding.

• To process the same multicast information from different peers received on different interfaces of the

same device, every multicast packet undergoes a reverse path forwarding (RPF) check on the incoming interface. The result of the RPF check 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.

NOTE:

For more information about the RPF mechanism, see the chapters “Multicast routing and forwarding configuration” and “IPv6 multicast routing and forwarding configuration.”

11

Multi-instance multicast

Multi-instance multicast refers to multicast in virtual private networks (VPNs).

Introduction to the multi-instance concept

VPN networks must be isolated from one another and from the public network.

Figure 10 Networking diagram for VPN

VPN A

CE a2

CE b3

VPN BVPN B

CE a3

PE 3

VPN A

CE b1

CE a1

VPN A

CE b2

PE 1

PE 2

P

Public network

As shown in Figure 10, VPN A and VPN B separately access the public network through PE devices. The devices in the network are as follows:

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

CE device serves its own network and maintains only one set of forwarding mechanism.

• The PE devices connect to the public network and the VPN networks at the same time. Each PE

device must strictly distinguish the information for different networks, and must maintain a separate forwarding mechanism for each network. On a PE device, a set of software and hardware that serves the same network forms an instance. Multiple instances exist on a PE device at the same time, and an instance resides on different PE devices.

Multi-instance application in multicast

With multi-instance multicast enabled, a PE can do the following operations:

• Maintain a set of independent multicast forwarding mechanisms for each instance, including

various multicast protocols, a list of PIM neighbors, and a multicast routing table per instance. Each instance searches its own forwarding table or routing table to forward multicast data.

• Guarantee the isolation between different VPN instances.

12

• Implement information exchange and data conversion between the public network and VPN

instances.

NOTE:

Only one set of unified multicast service runs on a non-PE device. It is called a “public network.”

The configuration made in VPN instance view takes effect only on the VPN instance interface. An

interface that does not belong to any VPN instance is called a “public network interface.”

13

IGMP snooping configuration

IGMP snooping overview

IGMP snooping is a multicast constraining mechanism that runs on Layer 2 devices to manage and control multicast groups.

Principle of IGMP snooping

By analyzing received IGMP messages, a Layer 2 switch that runs IGMP snooping establishes mappings between ports and multicast MAC addresses, and forwards multicast data based on these mappings.

When IGMP snooping is not running on the switch, multicast packets are flooded to all devices at Layer

2. When IGMP snooping runs on the switch, multicast packets for known multicast groups are multicast to the receivers, rather than being broadcast to all hosts, at Layer 2.

Figure 11 Before and after IGMP snooping is enabled on the Layer 2 device

Source

Multicast packet transmission

without IGMP Snooping

Host A

Receiver

Host B

Multicast packets

Multicast router

Layer 2 switch

Host C

Receiver

Multicast packet transmission

when IGMP Snooping runs

Source

Host A

Receiver

Host B

Multicast router

Layer 2 switch

Host C

Receiver

IGMP snooping forwards multicast data to only the receivers that require the data at Layer 2. It has the following advantages:

• Reducing Layer 2 broadcast packets, saving network bandwidth

• Enhancing the security of multicast traffic

• Facilitating the implementation of per-host accounting

14

Basic concepts in IGMP snooping

IGMP snooping related ports

In Figure 12, Router A connects to the multicast source, IGMP snooping runs on Switch A and Switch B, and Host A and Host C are receiver hosts—also called “multicast group members.”

Figure 12 IGMP snooping related ports

Router A Switch A

GE1/0/1 GE1/0/2

GE1/0/3

GE1/0/1

Source

Switch B

Router port

Member port

Multicast packets

Receiver

GE1/0/2

Host C

Host D

Receiver

Host A

Host B

IGMP snooping involves the following ports:

• Router port—A router port is a port on a Layer 2 switch that leads toward a Layer 3 multicast

device—DR or IGMP querier. In Figure 12, G

igabitEthernet 1/0/1 of Switch A and GigabitEthernet 1/0/1 of Switch B are router ports. Each switch registers all its local router ports in its router port list.

• Member port—A member port is a port on a Layer 2 switch that leads toward multicast group

members. In Figure 12, GigabitEthern

et 1/0/2 and GigabitEthernet 1/0/3 of Switch A and GigabitEthernet 1/0/2 of Switch B are member ports. Each switch registers all the member ports on the local device in its IGMP snooping forwarding table.

NOTE:

Whenever mentioned in this document, a router port is a port on the switch that leads the switch to a

Layer 3 multicast device, rather than a port on a router.

Unless otherwise specified, router/member ports mentioned in this document include static and

dynamic ports.

An IGMP-snooping-enabled switch deems that all its ports on which IGMP general queries with the

source IP address other than 0.0.0.0 or PIM hello messages are received are dynamic router ports. For more information about PIM hello messages, see the chapter “PIM configuration.”

15

piry

g

Aging timers for dynamic ports in IGMP snooping and related messages and actions

Timer Description

For each dynamic router

Dynamic router port aging timer

Dynamic member port aging timer

port, the switch sets a timer initialized to the dynamic router port aging time.

When a port dynamically joins a multicast group, the switch sets a timer for the port, which is initialized to the dynamic member port aging time.

NOTE:

The port aging mechanism of IGMP snooping works only for dynamic ports; a static port will never a out.

How IGMP snooping works

Message before ex

IGMP general query of which the source address is not 0.0.0.0 or PIM hello

IGMP membership report

Action after expiry

The switch removes this port from its router port list.

The switch removes this port from the IGMP snooping forwarding table.

e

A switch that runs IGMP snooping performs different actions when it receives different IGMP messages.

CAUTION:

The description about adding or deleting a port in this section is only for a dynamic port. Static ports can be added or deleted only through the specific configurations. For more information, see “Configuring static ports.”

When receiving a general query

The IGMP querier periodically sends IGMP general queries to all hosts and routers—224.0.0.1—on the local subnet to determine whether active multicast group members exist on the subnet.

After receiving an IGMP general query, the switch forwards it through all ports in the VLAN (except the port that received the query). The switch also performs the following judgment:

• If the port that received the query is a dynamic router port that exists in its router port list, the switch

resets the aging timer for this dynamic router port.

• If the port is not a dynamic router port that exists in its router port list, the switch adds it into its

router port list and sets an aging timer for this dynamic router port.

When receiving a membership report

A host sends an IGMP report to the IGMP querier in the following circumstances:

• If the host is already a member of a multicast group, the host responds with an IGMP report after

receiving an IGMP query.

• If the host wants to join a multicast group, the host sends an IGMP report to the IGMP querier to

announce that it is interested in the multicast information addressed to that group.

16

A

NOTE:

After receiving an IGMP report, the switch forwards it through all the router ports in the VLAN, resolves the address of the reported multicast group. The switch also performs the following judgment:

• If no entry in the forwarding table exists for the reported group, the switch creates an entry, adds

the port as a dynamic member port to the outgoing port list, and starts a member port aging timer for that port.

• If an entry in the forwarding table exists for the reported group but the port is not included in the

outgoing port list for that group, the switch adds the port as a dynamic member port to the outgoing port list and starts an aging timer for that port.

• If an entry in the forwarding table exists for the reported group and the port is included in the

outgoing port list, which means that this port is already a dynamic member port, the switch resets the aging timer for that port.

switch does not forward an IGMP report through a non-router port. The reason is that if the switch forwards a report message through a member port, all the attached hosts that are monitoring the reported multicast address suppress their own reports after receiving this report according to the IGMP report suppression mechanism. This prevents the switch from determining whether the reported multicast group still has active members attached to that port. For more information about the IGMP report suppression mechanism, see the chapter “IGMP configuration.”

When receiving a leave message

When an IGMPv1 host leaves a multicast group, the host does not send an IGMP leave message, so the switch cannot determine immediately that the host has left the multicast group. However, as the host stops sending IGMP reports as soon as it leaves a multicast group, the switch deletes the forwarding entry for the dynamic member port that corresponds to the host from the forwarding table when its aging timer expires.

When an IGMPv2 or IGMPv3 host leaves a multicast group, the host sends an IGMP leave message to the multicast router.

When the switch receives an IGMP leave message on a dynamic member port, the switch first determines whether an entry in the forwarding table exists for the group address in the message, and, if one exists, whether the outgoing port list contains the port.

• If the entry in the forwarding table does not exist or if the outgoing port list does not contain the

port, the switch discards the IGMP leave message instead of forwarding it to any port.

• If the entry in the forwarding table exists and the outgoing port list contains the port, the switch

forwards the leave message to all router ports in the native VLAN. Because the switch cannot determine whether any other hosts attached to the port are still monitoring that group address, the switch does not immediately remove the port from the outgoing port list of the entry in the forwarding table for that group. Instead, it resets the aging timer for the port.

After receiving the IGMP leave message from a host, the IGMP querier resolves the multicast group address in the message and sends an IGMP group-specific query to that multicast group through the port that received the leave message. After receiving the IGMP group-specific query, the switch forwards the query through all its router ports in the VLAN and all member ports for that multicast group. The switch also performs the following judgment on the port that received the IGMP leave message:

• If the port (a dynamic member port supposed) receives any IGMP report in response to the group-

specific query before its aging timer expires, it indicates that a host attached to the port is receiving or expecting to receive multicast data for that multicast group. The switch resets the aging timer of the port.

17

g

• If the port receives no IGMP report in response to the group-specific query before its aging timer

expires, it indicates that no hosts attached to the port are still monitoring that group address. The switch removes the port from the outgoing port list of the entry in the forwarding table for that multicast group when the aging timer expires.

IGMP snooping proxying

The IGMP snooping proxying function on an edge device reduces the number of IGMP reports and leave messages sent to its upstream device. The device configured with IGMP snooping proxying is called “IGMP snooping proxy.” It is a host from the perspective of its upstream device.

NOTE:

Even though an IGMP snooping proxy is a host from the perspective of its upstream device, the IGMP membership report suppression mechanism for hosts does not take effect on it. For more information about the IGMP report suppression mechanism for hosts, see the chapter “IGMP configuration.”

Figure 13 Network diagram for IGMP snooping proxying

As shown in Figure 13, Switch A works as an IGMP snooping proxy. As a host from the perspective of the querier Router A, Switch A represents its attached hosts to send membership reports and leave messages to Router A.

Table 6 IGMP message processing on an IGMP snooping proxy

IGMP messa

General query

Group-specific query

e Actions

When receiving an IGMP general query, the proxy forwards it to all ports but the receiving port. In addition, the proxy generates a report according to the group memberships it maintains and sends the report out all router ports.

In response to the IGMP group-specific query for a certain multicast group, the proxy sends the report to the group out all router ports if the forwarding entry for the group still contains a member port.

18

HP A5500 SI Switch, A5500 EI Switch Configuration Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Contents

Multicast overview

Introduction to multicast

Comparison of information transmission techniques

Features of multicast

Common notations in multicast

Advantages and applications of multicast

Multicast models

Multicast architecture

Multicast addresses

Multicast protocols

Multicast packet forwarding mechanism

Multi-instance multicast

Introduction to the multi-instance concept

Multi-instance application in multicast

IGMP snooping configuration

IGMP snooping overview

Principle of IGMP snooping

Basic concepts in IGMP snooping

How IGMP snooping works

IGMP snooping proxying