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Multicast Filtering 29

Figure4 The effect of multicast filtering

Multicast Filtering

and Your Switch

Your Switch provides automatic multicast filtering support using IGMP

(Internet Group Management Protocol) Snooping . It also supports IGMP

query mode.

Snooping Mode

Snooping Mode allows your Switch to fo rward multicast packets only to

the appropriate ports. The Switch “snoops” on e xchanges between

endstations and an IGMP device, typically a router, to find out the po rts

that wish to join a multicast group and then sets its filters accordingly

Query Mode

Query mode allows the Switch to function as the Querier if it has the

lowest IP address in the subnetwork to which it belongs.

IGMP querying is disabled by default on the Sw itch 4200. This helps

prevent interoperability issues with core products that may not follow the

lowest IP address election method.

You can enable or disable IGMP query mode for all Switch units in the

stack using the queryMode command on the command line interface

IGMP menu.

You would enable query mode if you wish to run multicast sessions in a

network that does not contain any IGMP routers (or queriers). This

Contents

Main 3Com Corporation 5400 Bayfront Plaza Santa Clara, California 95052-8145 C ABOUT THIS GUIDE 1 2 3 4 5 6 7 8 9 A B C G I A BOUT T HIS G Conventions Tabl e 1 Notice Icons Tabl e 2 Text Conventions Related Documentation Documentation Comments Product Registration I Page 1 What is Management Software? Switch Features Explained Page Page Page Page Page 2 Port Features Page Page Aggregated Links Page Page Page Page 3 What is an IP Multicast? Multicast Filtering Page IGMP Multicast Filtering Page Page 4 Spanning Tree Protocol (STP) What is STP? Page How STP Works Page Page Page Page Page Default Behavior Using STP on a Network with Multiple VLANs Page Page 5 What is the Switch Database? How Switch Database Entries Get Added Switch Database Entry States 6 What is Traffic Prioritization? How Traffic Prioritization Works Page Traffic Prioritization and your Switch Page Page 7 S RMON What is RMON? Benefits of RMON RMON and the Switch Page Page Hardware Status Monitoring Hardware Status Monitoring 59 Figure13 Example CLI screen text Figure14 Example of an individual unit system summary screen Page 8 What are VLANs? Benefits of VLANs VLANs and Your Switch Page Page VLAN Configuration Page Page 9 How Your Switch Obtains IP Information How Automatic IP Configuration Works Page Important Considerations II Page A Configuration Rules for Gigabit Ethernet Gigabit Ethernet is designed to run over several media: (3.1 miles). Support for distances over 5 km is supp orted depending on the module specification. The different types of Gigabit Ethernet media and their s pecifications are detailed in Tabl e 7. Configuration Rules for Fast Ethernet Page Page B Simple Network Configuration Simple Network Configuration Examples 81 Collapsed Backbone Switch Example DualSpeed Hub 500 Switch4400 stack Switch4200 stack Figure22 Using the Switch 4200 as a collapsed backbone Page Advanced Network Configuration Page C IP Addresses Page Page Subnets and Subnet Masks Page Default Gateway s G Page Page Page Page Page Page Page Page Page I Numbers A B C L M N O P T V