DIGITAL GIGAswitch/Router User Reference Manual
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Chapter 12
Multicast Routing
Configuration
Guide
IP Multicast Overview
Multicast routing on the GSR is supported through DVMRP and IGMP. IGMP is used to
determine host membership on directly attached subnets. DVMRP is used to determine
forwarding of multicast traffic between GSRs.
This chapter:
•
Provides an overview of the GSR’s implementation of the Internet Group Management
Protocol (IGMP)
•
Provides an overview of the GSR’s implementation of the Distance Vector Multicast
Routing Protocol (DVMRP)
•
Discusses configuring DVMRP routing on the GSR
•
Discusses configuring IGMP on the GSR
IGMP Overview
The GSR supports IGMP Version 2.0 as defined in RFC 2236. IGMP is run on a per-IP
interface basis. An IP interface can be configured to run just IGMP and not DVMRP. Since
multiple physical ports (VLANs) can be configured with the same IP interface on the GSR,
IGMP keeps track of multicast host members on a per-port basis. Ports belonging to an IP
VLAN without any IGMP membership will not be forwarded any multicast traffic.
