Technical Guide IGMP and MLD Feature Overview and Configuration Guide Introduction Allied Telesis routers and managed Layer 3 switches use IGMP (Internet Group Management Protocol) and MLD (Multicast Listener Discovery) to track which multicast groups their clients belong to. This enables them to send the correct multimedia streams to the correct destinations. IGMP is used for IPv4 multicasting, and MLD is used for IPv6 multicasting. This guide describes basic and advanced IGMP and MLD configuration, in the following major sections: an overview of IGMP/MLD and definitions of some of the IGMP/MLD terminology examples and discussion of the most common IGMP functionality—IGMP/MLD snooping, IGMP/ MLD Querier behaviour and selection, and IGMP/MLD proxy examples and discussion of the advanced functionality available through the feature-rich IGMP/ MLD implementation in AlliedWare Plus™ information for debugging information about the STP state of the simple three-switch ring used in most examples information about IGMPv3/MLDv2 Products and software version that apply to this guide This guide applies to all AlliedWare Plus™ products, running version 5.4.4 or later. Feature support may change in later software versions. For the latest information, see the following documents: The product’s Datasheet The product’s Command Reference C613-22074-00 REV E alliedtelesis.com IGMP and MLD Related documents The following documents give more information about the multicasting features on AlliedWare Plus products: Protocol Independent Multicast - Sparse Mode (PIM-SM) Feature Overview and Configuration Guide PIM Sparse Mode for IPv6 (PIM-SMv6) Feature Overview and Configuration Guide PIM Dense Mode (PIM-DM) Feature Overview and Configuration Guide Command Reference for each product These documents are available from the links above or on our website at alliedtelesis.com. C613-22074-00 REV E Introduction | Page 2 IGMP and MLD Content Introduction .........................................................................................................................................1 Products and software version that apply to this guide ...............................................................1 Related documents.......................................................................................................................2 Similarity of IGMP and MLD................................................................................................................5 Terminology...................................................................................................................................5 IGMP/MLD Overview...........................................................................................................................6 Queriers and Snoopers.................................................................................................................6 Messages......................................................................................................................................7 Choosing group addresses...........................................................................................................8 Limitation of MLD on AlliedWare Plus Switches ...............................................................................10 IGMP/MLD Snooping ........................................................................................................................10 Explanation of IGMP/MLD Snooping..........................................................................................11 Configuration example................................................................................................................12 Using the show command output to investigate IGMP state.....................................................15 Router ports................................................................................................................................18 Preventing occasional brief flooding of unregistered streams....................................................18 Limitations of IGMP snooping on x210 and x230 Series switches ............................................19 Multiple Potential IGMP/MLD Queriers .............................................................................................19 Example ......................................................................................................................................20 Explanation of multiple potential IGMP/MLD Queriers...............................................................22 IGMP Proxy .......................................................................................................................................26 Example ......................................................................................................................................26 Explanation of IGMP Proxy.........................................................................................................29 Multiple proxies...........................................................................................................................33 Query Solicitation - Rapid Recovery From Topology Changes.........................................................34 How Query Solicitation works.....................................................................................................35 Why convergence takes so long without Query Solicitation ......................................................36 Speeding up IGMP convergence in a non-looped topology ......................................................41 Enabling Query Solicitation on multiple switches in a looped topology.....................................42 IGMP/MLD Filtering (controlling multicast distribution).....................................................................44 Example ......................................................................................................................................44 IGMP/MLD Throttling ........................................................................................................................47 Example of per-VLAN throttling ..................................................................................................47 Explanation of IGMP/MLD throttling...........................................................................................50 Per-port throttling of IGMP groups .............................................................................................51 Static IGMP/MLD ..............................................................................................................................52 C613-22074-00 REV E Introduction | Page 3 IGMP and MLD Example ......................................................................................................................................52 Explanation of static IGMP/MLD ................................................................................................55 Static router ports .......................................................................................................................59 How Clients Leave Groups: Queries and Timers ..............................................................................60 Overview of leave process..........................................................................................................60 Querier timer values....................................................................................................................61 Snooper timer values..................................................................................................................62 Comparing the Querier and Snooper timers...............................................................................63 Consequences for high-loss and high-lag networks ..................................................................63 IGMP/MLD Fast Leave ......................................................................................................................64 Example ......................................................................................................................................64 Explanation of IGMP/MLD Fast Leave........................................................................................66 Immediate Leave and Fast Leave...............................................................................................69 Configurable IGMP/MLD Timers and Counters ................................................................................70 Timer and counter relationships .................................................................................................70 Default values .............................................................................................................................71 Last Member Query Count and Last Member Query Interval.....................................................73 Robustness Variable ...................................................................................................................74 Default Query Interval .................................................................................................................76 Max Query Response Interval.....................................................................................................77 Group Membership Interval ........................................................................................................78 Stopping Snoopers from Snooping Non-IGMP Messages