H3C S5500-EI Series Ethernet Switches. IP Multicast. Configuration Guide. Hangzhou H3C Technologies Co., Ltd.

Transcription

1 H3C S5500-EI Series Ethernet Switches IP Multicast Configuration Guide Hangzhou H3C Technologies Co., Ltd. Document Version: C-1.03 Product Version: Release 2202

2 Copyright , Hangzhou H3C Technologies Co., Ltd. and its licensors All Rights Reserved No part of this manual may be reproduced or transmitted in any form or by any means without prior written consent of Hangzhou H3C Technologies Co., Ltd. Trademarks H3C,, Aolynk,, H 3 Care,, TOP G,, IRF, NetPilot, Neocean, NeoVTL, SecPro, SecPoint, SecEngine, SecPath, Comware, Secware, Storware, NQA, VVG, V 2 G, V n G, PSPT, XGbus, N-Bus, TiGem, InnoVision and HUASAN are trademarks of Hangzhou H3C Technologies Co., Ltd. All other trademarks that may be mentioned in this manual are the property of their respective owners. Notice The information in this document is subject to change without notice. Every effort has been made in the preparation of this document to ensure accuracy of the contents, but all statements, information, and recommendations in this document do not constitute the warranty of any kind, express or implied.

3 Preface The H3C S5500-EI documentation set includes 10 configuration guides, which describe the software features for the S5500-EI Series Ethernet Switches and guide you through the software configuration procedures. These configuration guides also provide configuration examples to help you apply software features to different network scenarios. The IP Multicast Configuration Guide describes IP multicast fundamentals and configuration. It covers the IPv4 multicast configuration and IPv6 multicast configuration. With multicast, you can implement efficient point-to-multipoint data transmission in your network. This preface includes: Audience Document Organization Conventions About the H3C S5500-EI Documentation Set Obtaining Documentation Documentation Feedback Audience This documentation set is intended for: Network planners Field technical support and servicing engineers Network administrators working with the S5500-EI series Document Organization The IP Multicast Configuration Guide comprises these parts: Mulitcast Overview IGMP Snooping Configuration Multicast VLAN Configuration Multicast Routing and Forwarding Configuration IGMP Configuration PIM Configuration MSDP Configuration MBGP Configuration MLD Snooping Configuration IPv6 Multicast VLAN Configuration IPv6 Multicast Routing and Forwarding Configuration MLD Configuration IPv6 PIM Configuration IPv6 MBGP Configuration Conventions This section describes the conventions used in this documentation set. Command conventions Boldface Convention Description Bold text represents commands and keywords that you enter literally as shown.

4 Convention Description italic [ ] { x y... } [ x y... ] { x y... } * [ x y... ] * &<1-n> Italic text represents arguments that you replace with actual values. Square brackets enclose syntax choices (keywords or arguments) that are optional. Braces enclose a set of required syntax choices separated by vertical bars, from which you select one. Square brackets enclose a set of optional syntax choices separated by vertical bars, from which you select one or none. Asterisk marked braces enclose a set of required syntax choices separated by vertical bars, from which you select at least one. Asterisk marked square brackets enclose optional syntax choices separated by vertical bars, from which you may select multiple choices or none. The argument or keyword and argument combination before the ampersand (&) sign can be entered 1 to n times. # A line that starts with a pound (#) sign is comments. Symbols Convention Description Means reader be extremely careful. Improper operation may cause bodily injury. Means reader be careful. Improper operation may cause data loss or damage to equipment. Means a complementary description. About the H3C S5500-EI Documentation Set The H3C S5500-EI documentation set also includes: Category Documents Purposes Product description and specifications Marketing brochures Technology white papers PSR150-A [ PSR150-D ] Power Modules User Manual RPS User Manual RPS Ordering Information for H3C Low-End Ethernet Switches H3C Low End Series Ethernet Switches Pluggable Modules Manual Interface Card User Manual Describe product specifications and benefits. Provide an in-depth description of software features and technologies. Describes the appearances, features, specifications, installation, and removal of the pluggable 150W power modules available for the products. Describes the appearances, features, and specifications of the RPS units available for the products. Provides the RPS and switch compatibility matrix and RPS cable specifications. Describes the models, appearances, and specifications of the pluggable modules available for the products. Describes the appearance and specifications of the interface card.

5 Category Documents Purposes Hardware installation Software configuration Operations and maintenance H3C S5500-EI Quick Start S5500-EI Series Ethernet Switches Installation Manual Pluggable SFP[SFP+][XFP] Transceiver Modules Installation Guide Interface Card User Manual Configuration guides Command references H3C Series Ethernet Switches Login Password Recovery Manual Release notes Provides regulatory information and the safety instructions that must be followed during installation. Guides you through initial installation and setup procedures to help you quickly set up and use your device with the minimum configuration. Provides a complete guide to hardware installation and hardware specifications. Guides you through installing SFP/SFP+/XFP transceiver modules. Describes how to install the interface card. Describe software features and configuration procedures. Provide a quick reference to all available commands. Tells how to find the lost password or recover the password when the login password is lost. Provide information about the product release, including the version history, hardware and software compatibility matrix, version upgrade information, technical support information, and software upgrading. Obtaining Documentation You can access the most up-to-date H3C product documentation on the World Wide Web at Click the links on the top navigation bar to obtain different categories of product documentation: [Technical Support & Documents > Technical Documents] Provides hardware installation, software upgrading, and software feature configuration and maintenance documentation. [Products & Solutions] Provides information about products and technologies, as well as solutions. [Technical Support & Documents > Software Download] Provides the documentation released with the software version. Documentation Feedback You can your comments about product documentation to info@h3c.com. We appreciate your comments.

6 Table of Contents 1 Multicast Overview 1-1 Introduction to Multicast 1-1 Comparison of Information Transmission Techniques 1-1 Features of Multicast 1-3 Common Notations in Multicast 1-4 Advantages and Applications of Multicast 1-4 Multicast Models 1-5 Multicast Architecture 1-5 Multicast Addresses 1-6 Multicast Protocols 1-10 Multicast Packet Forwarding Mechanism IGMP Snooping Configuration 2-1 IGMP Snooping Overview 2-1 Principle of IGMP Snooping 2-1 Basic Concepts in IGMP Snooping 2-2 How IGMP Snooping Works 2-3 Protocols and Standards 2-5 IGMP Snooping Configuration Task List 2-5 Configuring Basic Functions of IGMP Snooping 2-7 Configuration Prerequisites 2-7 Enabling IGMP Snooping 2-7 Configuring the Version of IGMP Snooping 2-7 Configuring IGMP Snooping Port Functions 2-8 Configuration Prerequisites 2-8 Configuring Aging Timers for Dynamic Ports 2-8 Configuring Static Ports 2-9 Configuring Simulated Joining 2-10 Configuring Fast Leave Processing 2-11 Configuring IGMP Snooping Querier 2-12 Configuration Prerequisites 2-12 Enabling IGMP Snooping Querier 2-12 Configuring IGMP Queries and Responses 2-13 Configuring Source IP Address of IGMP Queries 2-14 Configuring an IGMP Snooping Policy 2-15 Configuration Prerequisites 2-15 Configuring a Multicast Group Filter 2-15 Configuring Multicast Source Port Filtering 2-16 Configuring the Function of Dropping Unknown Multicast Data 2-17 Configuring IGMP Report Suppression 2-17 Configuring Maximum Multicast Groups that Can Be Joined on a Port 2-18 Configuring Multicast Group Replacement 2-18 Displaying and Maintaining IGMP Snooping 2-19 IGMP Snooping Configuration Examples 2-20 i

7 Configuring Group Policy and Simulated Joining 2-20 Static Port Configuration 2-23 IGMP Snooping Querier Configuration 2-26 Troubleshooting IGMP Snooping Configuration 2-28 Switch Fails in Layer 2 Multicast Forwarding 2-28 Configured Multicast Group Policy Fails to Take Effect 2-29 Appendix 2-29 Processing of Multicast Protocol Messages Multicast VLAN Configuration 3-1 Introduction to Multicast VLAN 3-1 Multicast VLAN Configuration Task List 3-3 Configuring Sub-VLAN-Based Multicast VLAN 3-3 Configuration Prerequisites 3-3 Configuring Sub-VLAN-Based Multicast VLAN 3-3 Configuring Port-Based Multicast VLAN 3-4 Configuration Prerequisites 3-4 Configuring User Port Attributes 3-5 Configuring Multicast VLAN Ports 3-5 Displaying and Maintaining Multicast VLAN 3-7 Multicast VLAN Configuration Examples 3-7 Sub-VLAN-Based Multicast VLAN Configuration 3-7 Port-Based Multicast VLAN Configuration Multicast Routing and Forwarding Configuration 4-1 Multicast Routing and Forwarding Overview 4-1 Introduction to Multicast Routing and Forwarding 4-1 RPF Check Mechanism 4-1 Multicast Static Routes 4-4 Multicast Traceroute 4-6 Configuration Task List 4-7 Enabling IP Multicast Routing 4-7 Configuring Multicast Routing and Forwarding 4-7 Configuration Prerequisites 4-7 Configuring Multicast Static Routes 4-8 Configuring a Multicast Routing Policy 4-8 Configuring a Multicast Forwarding Range 4-9 Configuring the Multicast Forwarding Table Size 4-10 Tracing a Multicast Path 4-10 Displaying and Maintaining Multicast Routing and Forwarding 4-11 Configuration Examples 4-12 Changing an RPF Route 4-12 Creating an RPF Route 4-14 Troubleshooting Multicast Routing and Forwarding 4-16 Multicast Static Route Failure 4-16 Multicast Data Fails to Reach Receivers IGMP Configuration 5-1 IGMP Overview 5-1 IGMP Versions 5-1 ii

8 Introduction to IGMPv1 5-2 Enhancements in IGMPv2 5-3 Enhancements in IGMPv3 5-4 IGMP SSM Mapping 5-5 IGMP Proxying 5-6 Protocols and Standards 5-7 IGMP Configuration Task List 5-8 Configuring Basic Functions of IGMP 5-8 Configuration Prerequisites 5-8 Enabling IGMP 5-9 Configuring IGMP Versions 5-9 Configuring Static Joining 5-10 Configuring a Multicast Group Filter 5-11 Configuring the Maximum Number of Multicast Groups on an Interface 5-11 Adjusting IGMP Performance 5-12 Configuration Prerequisites 5-12 Configuring IGMP Message Options 5-13 Configuring IGMP Query and Response Parameters 5-14 Configuring IGMP Fast Leave Processing 5-17 Configuring IGMP SSM Mapping 5-17 Configuration Prerequisites 5-17 Enabling SSM Mapping 5-17 Configuring SSM Mappings 5-18 Configuring IGMP Proxying 5-18 Configuration Prerequisites 5-18 Enabling IGMP Proxying 5-18 Configuring Multicast Forwarding on a Downstream Interface 5-19 Displaying and Maintaining IGMP 5-20 IGMP Configuration Examples 5-21 Basic IGMP Functions Configuration Example 5-21 SSM Mapping Configuration Example 5-23 IGMP Proxying Configuration Example 5-26 Troubleshooting IGMP 5-28 No Membership Information on the Receiver-Side Router 5-28 Inconsistent Memberships on Routers on the Same Subnet PIM Configuration 6-1 PIM Overview 6-1 Introduction to PIM-DM 6-2 How PIM-DM Works 6-2 Introduction to PIM-SM 6-5 How PIM-SM Works 6-5 Introduction to Administrative Scoping 6-11 SSM Model Implementation in PIM 6-13 Protocols and Standards 6-14 Configuring PIM-DM 6-14 PIM-DM Configuration Task List 6-14 Configuration Prerequisites 6-15 Enabling PIM-DM 6-15 iii

9 Enabling State-Refresh Capability 6-16 Configuring State-Refresh Parameters 6-16 Configuring PIM-DM Graft Retry Period 6-17 Configuring PIM-SM 6-17 PIM-SM Configuration Task List 6-17 Configuration Prerequisites 6-18 Enabling PIM-SM 6-18 Configuring an RP 6-19 Configuring a BSR 6-21 Configuring Administrative Scoping 6-25 Configuring Multicast Source Registration 6-27 Disabling SPT Switchover 6-28 Configuring PIM-SSM 6-29 PIM-SSM Configuration Task List 6-29 Configuration Prerequisites 6-29 Enabling PIM-SM 6-29 Configuring the SSM Group Range 6-30 Configuring PIM Common Features 6-31 PIM Common Feature Configuration Task List 6-31 Configuration Prerequisites 6-31 Configuring a Multicast Data Filter 6-32 Configuring a Hello Message Filter 6-32 Configuring PIM Hello Options 6-33 Configuring PIM Common Timers 6-35 Configuring Join/Prune Message Sizes 6-37 Displaying and Maintaining PIM 6-37 PIM Configuration Examples 6-38 PIM-DM Configuration Example 6-38 PIM-SM Non-Scoped Zone Configuration Example 6-41 PIM-SM Admin-Scope Zone Configuration Example 6-46 PIM-SSM Configuration Example 6-52 Troubleshooting PIM Configuration 6-55 Failure of Building a Multicast Distribution Tree Correctly 6-55 Multicast Data Abnormally Terminated on an Intermediate Router 6-56 RPs Unable to Join SPT in PIM-SM 6-56 RPT Establishment Failure or Source Registration Failure in PIM-SM MSDP Configuration 7-1 MSDP Overview 7-1 Introduction to MSDP 7-1 How MSDP Works 7-2 Protocols and Standards 7-7 MSDP Configuration Task List 7-7 Configuring Basic Functions of MSDP 7-8 Configuration Prerequisites 7-8 Enabling MSDP 7-8 Creating an MSDP Peer Connection 7-9 Configuring a Static RPF Peer 7-9 Configuring an MSDP Peer Connection 7-10 iv

10 Configuration Prerequisites 7-10 Configuring MSDP Peer Description 7-10 Configuring an MSDP Mesh Group 7-10 Configuring MSDP Peer Connection Control 7-11 Configuring SA Messages Related Parameters 7-12 Configuration Prerequisites 7-12 Configuring SA Message Content 7-12 Configuring SA Request Messages 7-13 Configuring SA Message Filtering Rules 7-13 Configuring the SA Cache Mechanism 7-14 Displaying and Maintaining MSDP 7-15 MSDP Configuration Examples 7-15 Inter-AS Multicast Configuration Leveraging BGP Routes 7-15 Inter-AS Multicast Configuration Leveraging Static RPF Peers 7-20 Anycast RP Configuration 7-23 SA Message Filtering Configuration 7-27 Troubleshooting MSDP 7-30 MSDP Peers Stay in Down State 7-30 No SA Entries in the Router s SA Cache 7-31 Inter-RP Communication Faults in Anycast RP Application MBGP Configuration 8-1 MBGP Overview 8-1 Protocols and Standards 8-2 MBGP Configuration Task List 8-2 Configuring MBGP Basic Functions 8-3 Prerequisites 8-3 Configuration Procedure 8-3 Controlling Route Advertisement and Reception 8-3 Prerequisites 8-3 Configuring MBGP Route Redistribution 8-3 Configure Default Route Redistribution into MBGP 8-4 Configuring MBGP Route Summarization 8-5 Advertising a Default Route to an IPv4 MBGP Peer or Peer Group 8-5 Configuring Outbound MBGP Route Filtering 8-6 Configuring Inbound MBGP Route Filtering 8-7 Configuring MBGP Route Dampening 8-8 Configuring MBGP Route Attributes 8-8 Prerequisites 8-8 Configuring MBGP Route Preferences 8-8 Configuring the Default Local Preference 8-9 Configuring the MED Attribute 8-9 Configuring the Next Hop Attribute 8-10 Configuring the AS-PATH Attribute 8-10 Tuning and Optimizing MBGP Networks 8-11 Prerequisites 8-11 Configuring MBGP Soft Reset 8-11 Configuring the Maximum Number of MBGP Routes for Load Balancing 8-12 Configuring a Large Scale MBGP Network 8-13 v

11 Prerequisites 8-13 Configuring IPv4 MBGP Peer Groups 8-13 Configuring MBGP Community 8-14 Configuring an MBGP Route Reflector 8-15 Displaying and Maintaining MBGP 8-15 Displaying MBGP 8-15 Resetting MBGP Connections 8-17 Clearing MBGP Information 8-17 MBGP Configuration Example MLD Snooping Configuration 9-1 MLD Snooping Overview 9-1 Introduction to MLD Snooping 9-1 Basic Concepts in MLD Snooping 9-2 How MLD Snooping Works 9-3 Protocols and Standards 9-5 MLD Snooping Configuration Task List 9-5 Configuring Basic Functions of MLD Snooping 9-7 Configuration Prerequisites 9-7 Enabling MLD Snooping 9-7 Configuring the Version of MLD Snooping 9-8 Configuring MLD Snooping Port Functions 9-8 Configuration Prerequisites 9-8 Configuring Aging Timers for Dynamic Ports 9-9 Configuring Static Ports 9-10 Configuring Simulated Joining 9-11 Configuring Fast Leave Processing 9-11 Configuring MLD Snooping Querier 9-12 Configuration Prerequisites 9-12 Enabling MLD Snooping Querier 9-13 Configuring MLD Queries and Responses 9-13 Configuring Source IPv6 Addresses of MLD Queries 9-14 Configuring an MLD Snooping Policy 9-15 Configuration Prerequisites 9-15 Configuring an IPv6 Multicast Group Filter 9-15 Configuring IPv6 Multicast Source Port Filtering 9-16 Configuring Dropping Unknown IPv6 Multicast Data 9-17 Configuring MLD Report Suppression 9-18 Configuring Maximum Multicast Groups that Can Be Joined on a Port 9-18 Configuring IPv6 Multicast Group Replacement 9-19 Displaying and Maintaining MLD Snooping 9-20 MLD Snooping Configuration Examples 9-21 Configuring IPv6 Group Policy and Simulated Joining 9-21 Static Port Configuration 9-23 MLD Snooping Querier Configuration 9-27 Troubleshooting MLD Snooping 9-28 Switch Fails in Layer 2 Multicast Forwarding 9-28 Configured IPv6 Multicast Group Policy Fails to Take Effect 9-29 Appendix 9-29 vi

12 Processing of IPv6 Multicast Protocol Messages IPv6 Multicast VLAN Configuration 10-1 Introduction to IPv6 Multicast VLAN 10-1 IPv6 Multicast VLAN Configuration Task List 10-3 Configuring IPv6 Sub-VLAN-Based IPv6 Multicast VLAN 10-3 Configuration Prerequisites 10-3 Configuring Sub-VLAN-Based IPv6 Multicast VLAN 10-3 Configuring Port-Based IPv6 Multicast VLAN 10-4 Configuration Prerequisites 10-4 Configuring User Port Attributes 10-5 Configuring IPv6 Multicast VLAN Ports 10-5 Displaying and Maintaining IPv6 Multicast VLAN 10-7 IPv6 Multicast VLAN Configuration Examples 10-7 Sub-VLAN-Based Multicast VLAN Configuration Example 10-7 Port-Based Multicast VLAN Configuration Example IPv6 Multicast Routing and Forwarding Configuration 11-1 IPv6 Multicast Routing and Forwarding Overview 11-1 Introduction to IPv6 Multicast Routing and Forwarding 11-1 RPF Check Mechanism 11-1 Configuration Task List 11-4 Enabling IPv6 Multicast Routing 11-4 Configuring IPv6 Multicast Routing and Forwarding 11-5 Configuration Prerequisites 11-5 Configuring an IPv6 Multicast Routing Policy 11-5 Configuring an IPv6 Multicast Forwarding Range 11-5 Configuring the IPv6 Multicast Forwarding Table Size 11-6 Displaying and Maintaining IPv6 Multicast Routing and Forwarding 11-7 Troubleshooting IPv6 Multicast Policy Configuration 11-8 Abnormal Termination of IPv6 Multicast Data MLD Configuration 12-1 MLD Overview 12-1 MLD Versions 12-1 How MLDv1 Works 12-2 How MLDv2 Works 12-3 MLD Message Types 12-5 MLD SSM Mapping 12-7 MLD Proxying 12-8 Protocols and Standards 12-9 Configuration Task List Configuring Basic Functions of MLD Configuration Prerequisites Enabling MLD Configuring the MLD Version Configuring Static Joining Configuring an IPv6 Multicast Group Filter Configuring the Maximum Number of IPv6 Multicast Groups on an Interface Adjusting MLD Performance vii

13 Configuration Prerequisites Configuring MLD Message Options Configuring MLD Query and Response Parameters Configuring MLD Fast Leave Processing Configuring MLD SSM Mapping Configuration Prerequisites Enabling MLD SSM Mapping Configuring MLD SSM Mappings Configuring MLD Proxying Configuration Prerequisites Enabling MLD Proxying Configuring IPv6 Multicast Forwarding on a Downstream Interface Displaying and Maintaining MLD Configuration MLD Configuration Examples Basic MLD Functions Configuration Example MLD SSM Mapping Configuration Example MLD Proxying Configuration Example Troubleshooting MLD No Member Information on the Receiver-Side Router Inconsistent Memberships on Routers on the Same Subnet IPv6 PIM Configuration 13-1 IPv6 PIM Overview 13-1 Introduction to IPv6 PIM-DM 13-2 How IPv6 PIM-DM Works 13-2 Introduction to IPv6 PIM-SM 13-5 How IPv6 PIM-SM Works 13-6 SSM Model Implementation in IPv6 PIM Protocols and Standards Configuring IPv6 PIM-DM IPv6 PIM-DM Configuration Task List Configuration Prerequisites Enabling IPv6 PIM-DM Enabling State-Refresh Capability Configuring State Refresh Parameters Configuring IPv6 PIM-DM Graft Retry Period Configuring IPv6 PIM-SM IPv6 PIM-SM Configuration Task List Configuration Prerequisites Enabling IPv6 PIM-SM Configuring an RP Configuring a BSR Configuring IPv6 Multicast Source Registration Disabling SPT Switchover Configuring IPv6 PIM-SSM IPv6 PIM-SSM Configuration Task List Configuration Prerequisites Enabling IPv6 PIM-SM Configuring the IPv6 SSM Group Range viii

14 Configuring IPv6 PIM Common Features IPv6 PIM Common Feature Configuration Task List Configuration Prerequisites Configuring an IPv6 Multicast Data Filter Configuring a Hello Message Filter Configuring IPv6 PIM Hello Options Configuring IPv6 PIM Common Timers Configuring Join/Prune Message Sizes Displaying and Maintaining IPv6 PIM IPv6 PIM Configuration Examples IPv6 PIM-DM Configuration Example IPv6 PIM-SM Configuration Example IPv6 PIM-SSM Configuration Example Troubleshooting IPv6 PIM Configuration Failure of Building a Multicast Distribution Tree Correctly IPv6 Multicast Data Abnormally Terminated on an Intermediate Router RPs Unable to Join SPT in IPv6 PIM-SM RPT Establishment Failure or Source Registration Failure in IPv6 PIM-SM IPv6 MBGP Configuration 14-1 IPv6 MBGP Overview 14-1 IPv6 MBGP Configuration Task List 14-2 Configuring IPv6 MBGP Basic Functions 14-2 Configuration Prerequisites 14-2 Configuring an IPv6 MBGP Peer 14-3 Configuring a Preferred Value for Routes from a Peer/Peer Group 14-3 Controlling Route Distribution and Reception 14-4 Configuration Prerequisites 14-4 Injecting a Local IPv6 MBGP Route 14-4 Configuring IPv6 MBGP Route Redistribution 14-4 Configuring IPv6 MBGP Route Summarization 14-5 Advertising a Default Route to a Peer or Peer Group 14-5 Configure Outbound IPv6 MBGP Route Filtering 14-6 Configuring Inbound IPv6 MBGP Route Filtering 14-7 Configuring IPv6 MBGP Route Dampening 14-8 Configuring IPv6 MBGP Route Attributes 14-9 Configuration Prerequisites 14-9 Configuring IPv6 MBGP Route Preferences 14-9 Configuring the Default Local Preference 14-9 Configuring the MED Attribute Configuring the NEXT_HOP Attribute Configuring the AS_PATH Attribute Tuning and Optimizing IPv6 MBGP Networks Configuration Prerequisites Configuring IPv6 MBGP Soft Reset Configuring the Maximum Number of Equal-Cost Routes for Load-Balancing Configuring a Large Scale IPv6 MBGP Network Configuration Prerequisites Configuring an IPv6 MBGP Peer Group ix

15 Configuring IPv6 MBGP Community Configuring an IPv6 MBGP Route Reflector Displaying and Maintaining IPv6 MBGP Displaying IPv6 MBGP Resetting IPv6 MBGP Connections Clearing IPv6 MBGP Information IPv6 MBGP Configuration Example Index 15-1 x

16 1 Multicast Overview This manual chiefly focuses on the IP multicast technology and device operations. Unless otherwise stated, the term multicast in this document refers to IP multicast. Introduction to Multicast As a technique coexisting with unicast and broadcast, the multicast technique effectively addresses the issue of point-to-multipoint data transmission. By allowing high-efficiency point-to-multipoint data transmission over a network, multicast greatly saves network bandwidth and reduces network load. With the multicast technology, a network operator can easily provide new value-added services, such as live Webcasting, Web TV, distance learning, telemedicine, Web radio, real-time videoconferencing, and other bandwidth- and time-critical information services. Comparison of Information Transmission Techniques Unicast In unicast, the information source (Source in the figure) needs to send a separate copy of information to each host (Receiver in the figure) that wants the information, as shown in Figure 1-1. Figure 1-1 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 1-1

17 Assume that Host B, Host D and Host E need the information. A separate transmission channel needs to be established from the information source to each of these hosts. In unicast transmission, the traffic transmitted over the network is proportional to the number of hosts that need the information. If a large number of users need the information, the information source needs to send a copy of the same information to each of these users. This means a tremendous pressure on the information source and the network bandwidth. As we can see from the information transmission process, unicast is not suitable for batch transmission of information. Broadcast In broadcast, the information source sends information to all hosts on the subnet, even if some hosts do not need the information, as shown in Figure 1-2. Figure 1-2 Broadcast transmission 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, this also causes traffic flooding on the same subnet. Therefore, broadcast is disadvantageous in transmitting data to specific hosts; moreover, broadcast transmission is a significant waste of network resources. Multicast As discussed above, unicast and broadcast techniques are unable to provide point-to-multipoint data transmissions with the minimum network consumption. Multicast can well 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 packets are replicated only on nodes where the trees branch. Figure 1-3 shows the delivery of a data stream to receiver hosts through multicast. 1-2

18 Figure 1-3 Multicast transmission The multicast source (Source in the figure) sends only one copy of the information to a multicast group. Host B, Host D and Host E, which are receivers of the information, need to 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 sum up, the advantages of multicast are summarized as follows: Over unicast: As multicast traffic flows to the node the farthest possible from the source before it is replicated and distributed, an increase of the number of hosts will not increase the load of the source and will not remarkably add to network resource usage. Over broadcast: As multicast data is sent only to the receivers that need it, multicast uses the network bandwidth reasonably and enhances network security. In addition, data broadcast is confined to the same subnet, while multicast is not. Features of Multicast Multicast 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 referred to as a multicast source (Source in Figure 1-3). 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 (Receiver in Figure 1-3). 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 also manage multicast group memberships on stub subnets with attached group members. A multicast router itself can be a multicast group member. 1-3

19 For a better understanding of the multicast concept, you can assimilate multicast transmission to the transmission of TV programs, as shown in Table 1-1. Table 1-1 An analogy between TV transmission and multicast transmission TV transmission A TV station transmits a TV program through a channel. A user tunes the TV set to the channel. 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. Multicast transmission A multicast source sends multicast data to a multicast group. A receiver joins the 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. Common Notations in Multicast Two notations are commonly used in multicast: (*, G): Indicates a rendezvous point tree (RPT), or a multicast packet that any multicast source sends to multicast group G. Here * represents any multicast source, while 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, while G represents a specific multicast group. For details about the concepts RPT and SPT, see PIM Configuration or IPv6 PIM Configuration in the IP Multicast Configuration Guide. Advantages and Applications of Multicast Advantages of multicast Advantages of the multicast technique include: Enhanced efficiency: reduces the CPU load of information source servers and network devices. Optimal performance: reduces redundant traffic. Distributive application: enables point-to-multipoint applications at the price of minimum network resources. Applications of multicast Applications of the multicast technique include: Multimedia and streaming applications, such as Web TV, Web radio, and real-time video/audio conferencing. Communication for training and cooperative operations, such as distance learning and telemedicine. 1-4

20 Data warehouse and financial applications (stock quotes). Any other point-to-multipoint data distribution application. Multicast Models Based on how the receivers treat the multicast sources, there are three multicast models: 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 obtain multicast information addressed to that multicast group. In this model, receivers are not aware of the position of 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. From the view of a sender, the two models have the same multicast membership architecture. The SFM model functionally extends the ASM model: In the SFM 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. From the view of a receiver, multicast sources are not all valid: they are filtered. SSM model In the practical life, users may be interested in the multicast data from only certain multicast sources. The SSM model provides a transmission service that allows users to specify the multicast sources they are interested in at the client side. The radical difference between the SSM model and the ASM model is that in the SSM model, receivers already know 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 the receivers need to receive multicast data from? (multicast source discovery) How should information be transmitted to the receivers? (multicast routing) IP multicast falls in the scope of end-to-end service. The multicast architecture involves the following four parts: 1) Addressing mechanism: Information is sent from a multicast source to a group of receivers through a multicast address. 2) Host registration: Receiver hosts are allowed to join and leave multicast groups dynamically. This mechanism is the basis for group membership management. 3) Multicast routing: A multicast distribution tree (namely a forwarding path tree for multicast data on the network) is constructed for delivering multicast data from a multicast source to receivers. 1-5

21 4) Multicast applications: A software system that supports multicast applications, such as video conferencing, must be installed on multicast sources and receiver hosts, and the TCP/IP stack must support reception and transmission of multicast data. Multicast Addresses To allow communication between multicast sources and multicast group members, network-layer multicast addresses, namely, multicast IP addresses must be provided. 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 ( to ) for IPv4 multicast. The specific address blocks and usages are shown in Table 1-2. Table 1-2 Class D IP address blocks and description Address block to to Description Reserved permanent group addresses. The IP address is reserved, and other IP addresses can be used by routing protocols and for topology searching, protocol maintenance, and so on. Common permanent group addresses are listed in Table 1-3. 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 two types of designated group addresses: /8: SSM group addresses, and /8: Glop group addresses to Administratively scoped multicast addresses. These addresses are considered to be locally rather than globally unique, and can be reused in domains administered by different organizations without causing conflicts. For details, refer to RFC 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 , you get 255 multicast addresses for that AS. For more information, refer to RFC Table 1-3 Some reserved multicast addresses Address Description All systems on this subnet, including hosts and routers All multicast routers on this subnet 1-6

22 Address Description Unassigned Distance Vector Multicast Routing Protocol (DVMRP) routers Open Shortest Path First (OSPF) routers OSPF designated routers/backup designated routers Shared Tree (ST) routers ST hosts Routing Information Protocol version 2 (RIPv2) routers Mobile agents Dynamic Host Configuration Protocol (DHCP) server/relay agent All Protocol Independent Multicast (PIM) routers Resource Reservation Protocol (RSVP) encapsulation All Core-Based Tree (CBT) routers Designated Subnetwork Bandwidth Management (SBM) All SBMs Virtual Router Redundancy Protocol (VRRP) 2) IPv6 multicast addresses Figure 1-4 IPv6 multicast format Referring to Figure 1-4, the meanings of the fields of an IPv6 multicast address are as follows: 0xFF: The most significant 8 bits are , indicating that this address is an IPv6 multicast address. Figure 1-5 Format of the Flags field Flags: Referring to Figure 1-5, the following table describes the four bits of the Flags field. 1-7

23 Table 1-4 Description on the bits of the Flags field Bit Description 0 Reserved, set to 0 R P T When set to 0, it indicates that this address is an IPv6 multicast address without an 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) When set to 0, it indicates that this address is an IPv6 multicast address not based on 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-assigned by IANA When set to 1, it indicates that this address is a transient, or dynamically assigned IPv6 multicast address Scope: 4 bits, indicating the scope of the IPv6 internetwork for which the multicast traffic is intended. Possible values of this field are given in Table 1-5. Table 1-5 Values of the Scope field Value Meaning 0, F Reserved 1 Interface-local scope 2 Link-local scope 3 Subnet-local scope 4 Admin-local scope 5 Site-local scope 6, 7, 9 through D Unassigned 8 Organization-local scope E Global scope Group ID: 112 bits, IPv6 multicast group identifier that uniquely identifies an IPv6 multicast group in the scope defined by the Scope field. 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, however, 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 1-8

24 As defined by IANA, the high-order 24 bits of an IPv4 multicast MAC address are 0x01005E, bit 25 is 0, and the low-order 23 bits are the low-order 23 bits of a multicast IPv4 address. The IPv4-to-MAC mapping relation is shown in Figure 1-6. Figure 1-6 IPv4-to-MAC address mapping 5 bits lost 32-bit IPv4 address 1110 XXXX XXXX X XXXX XXXX XXXX XXXX XXXX XXXX 48-bit MAC address 23 bits mapped XXX XXXX XXXX XXXX XXXX XXXX 25-bit MAC address prefix The high-order four bits of a multicast IPv4 address are 1110, indicating that this address is a multicast address, and 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 MAC address. Therefore, in Layer 2 multicast forwarding, a device may receive some multicast data addressed for other IPv4 multicast groups, and such redundant data needs to be filtered by the upper layer. 2) IPv6 multicast MAC addresses The high-order 16 bits of an IPv6 multicast MAC address are 0x3333, and the low-order 32 bits are the low-order 32 bits of a multicast IPv6 address. Figure 1-7 shows an example of mapping an IPv6 multicast address, FF1E::F30E:101, to a MAC address. Figure 1-7 An example of IPv6-to-MAC address mapping 1-9

25 Multicast Protocols Generally, we refer to IP multicast working at the network layer as Layer 3 multicast and the corresponding multicast protocols as Layer 3 multicast protocols, which include IGMP/MLD, PIM/IPv6 PIM, MSDP, and MBGP/IPv6 MBGP; we refer to IP multicast working at the data link layer as Layer 2 multicast and the corresponding multicast protocols as Layer 2 multicast protocols, which include IGMP Snooping/MLD Snooping, and multicast VLAN/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. This section provides only general descriptions about applications and functions of the Layer 2 and Layer 3 multicast protocols in a network. For details of these protocols, refer to the related configuration manuals in the IP Multicast Configuration Guide. Layer 3 multicast protocols Layer 3 multicast protocols include multicast group management protocols and multicast routing protocols. Figure 1-8 describes where these multicast protocols are in a network. Figure 1-8 Positions of Layer 3 multicast protocols 1) Multicast management protocols Typically, the internet group management protocol (IGMP) or multicast listener discovery protocol (MLD) is used between hosts and Layer 3 multicast devices directly connected with 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 a loop-free data transmission path from a data source to multiple receivers, namely, a multicast distribution tree. 1-10

26 In the ASM model, multicast routes come in intra-domain routes and inter-domain routes. An intra-domain multicast routing protocol is used to discover multicast sources and build multicast distribution trees within an AS so as to deliver multicast data to receivers. Among a variety of mature intra-domain multicast routing protocols, protocol independent multicast (PIM) is a popular one. Based on the forwarding mechanism, PIM comes in two modes dense mode (often referred to as PIM-DM) and sparse mode (often referred to as PIM-SM). An inter-domain multicast routing protocol is used for delivery of multicast information between two ASs. So far, mature solutions include multicast source discovery protocol (MSDP) and multicast border gateway protocol (MBGP). MSDP is used to propagate multicast source information among different ASs, while MBGP, an extension of the Multi-protocol Border Gateway Protocol (MP-BGP), is used for exchanging multicast routing information among different ASs. For the SSM model, multicast routes are not divided into inter-domain routes and intra-domain routes. Since receivers know the position of the multicast source, channels established through PIM-SM are sufficient for multicast information transport. Layer 2 multicast protocols Layer 2 multicast protocols include IGMP Snooping/MLD Snooping and multicast VLAN/IPv6 multicast VLAN. Figure 1-9 shows where these protocols are in the network. Figure 1-9 Position of Layer 2 multicast protocols Source Multicast VLAN /IPv6 Multicast VLAN IGMP Snooping /MLD Snooping Receiver Receiver IPv4/IPv6 multicast packets 1) IGMP Snooping/MLD Snooping Running on Layer 2 devices, Internet Group Management Protocol Snooping (IGMP Snooping) and Multicast Listener Discovery Snooping (MLD Snooping) are multicast constraining mechanisms that manage and control multicast groups by listening to and analyzing IGMP or MLD messages exchanged between the hosts and Layer 3 multicast devices, thus effectively controlling the flooding of multicast data in a Layer 2 network. 2) Multicast VLAN/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. With the multicast VLAN or IPv6 multicast VLAN feature enabled on the Layer 2 device, the Layer 3 multicast device needs to send only one copy of multicast to the multicast VLAN or IPv6 multicast VLAN on the Layer 2 device. This avoids waste of network bandwidth and extra burden on the Layer 3 device. 1-11

27 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. Therefore, to deliver multicast packets to receivers located in different parts of the network, multicast routers on the forwarding path 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, the 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 is subject to 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. For details about the RPF mechanism, refer to Multicast Routing and Forwarding Configuration or IPv6 Multicast Routing and Forwarding Configuration in the IP Multicast Configuration Guide. 1-12

28 2 IGMP Snooping Configuration When configuring IGMP Snooping, go to the following sections for information you are interested in: IGMP Snooping Overview IGMP Snooping Configuration Task List Displaying and Maintaining IGMP Snooping IGMP Snooping Configuration Examples Troubleshooting IGMP Snooping Configuration IGMP Snooping Overview Internet Group Management Protocol Snooping (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 device running IGMP Snooping establishes mappings between ports and multicast MAC addresses and forwards multicast data based on these mappings. As shown in Figure 2-1, when IGMP Snooping is not running on the switch, multicast packets are broadcast to all devices at Layer 2. When IGMP Snooping is running on the switch, multicast packets for known multicast groups are multicast to the receivers, rather than broadcast to all hosts, at Layer 2. Figure 2-1 Before and after IGMP Snooping is enabled on the Layer 2 device Multicast packet transmission without IGMP Snooping Multicast packet transmission when IGMP Snooping runs Source Multicast router Source Multicast router Layer 2 switch Layer 2 switch Host A Receiver Host C Receiver Host A Receiver Host C Receiver Host B Host B Multicast packets 2-1

29 IGMP Snooping forwards multicast data to only the receivers requiring it at Layer 2. It brings the following advantages: Reducing Layer 2 broadcast packets, thus saving network bandwidth. Enhancing the security of multicast traffic. Facilitating the implementation of per-host accounting. Basic Concepts in IGMP Snooping IGMP Snooping related ports As shown in Figure 2-2, Router A connects to the multicast source, IGMP Snooping runs on Switch A and Switch B, Host A and Host C are receiver hosts (namely, multicast group members). Figure 2-2 IGMP Snooping related ports Router A GE1/0/1 Switch A GE1/0/2 Receiver GE1/0/3 Host A Source GE1/0/1 GE1/0/2 Receiver Host B Switch B Host C Router port Member port Multicast packets Host D Ports involved in IGMP Snooping, as shown in Figure 2-2, are described as follows: Router port: A router port is a port on an Ethernet switch that leads switch towards a Layer 3 multicast device (DR or IGMP querier). In the figure, GigabitEthernet 1/0/1 of Switch A and GigabitEthernet 1/0/1 of Switch B are router ports. The switch registers all its local router ports in its router port list. Member port: A member port is a port on an Ethernet switch that leads the switch towards multicast group members. In the figure, GigabitEthernet 1/0/2 and GigabitEthernet 1/0/3 of Switch A and GigabitEthernet 1/0/2 of Switch B are member ports. The switch registers all the member ports on the local device in its IGMP Snooping forwarding table. 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. 2-2

30 An IGMP-snooping-enabled switch deems that all its ports on which IGMP general queries with the source IP address other than or PIM hello messages are received to be dynamic router ports. For details about PIM hello messages, see PIM Configuration of the IP Multicast Configuration Guide. Aging timers for dynamic ports in IGMP Snooping and related messages and actions Table 2-1 Aging timers for dynamic ports in IGMP Snooping and related messages and actions Timer Description Message before expiry Action after expiry Dynamic router port aging timer For each dynamic router port, the switch sets a timer initialized to the dynamic router port aging time. IGMP general query of which the source address is not or PIM hello The switch removes this port from its router port list. When a port dynamically joins a multicast group, The switch removes this Dynamic member port aging timer the switch sets a timer for the port, which is IGMP membership report port from the IGMP Snooping forwarding initialized to the dynamic table. member port aging time. The port aging mechanism of IGMP Snooping works only for dynamic ports; a static port will never age out. How IGMP Snooping Works A switch running IGMP Snooping performs different actions when it receives different IGMP messages, as follows: 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 corresponding configurations. For details, see Configuring Static Ports. 2-3