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Chapter 7
Chapter 7 Multicast Routing Configuration
Guide
IP Multicast Overview
Multicast routing on the SSR 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 SSRs.
This chapter:
• Provides an overview of the SSR’s implementation of the Internet Group Manage-
ment Protocol (IGMP)
• Provides an overview of the SSR’s implementation of the Distance Vector Multicast
Routing Protocol (DVMRP)
• Discusses configuring DVMRP routing on the SSR
• Discusses configuring IGMP on the SSR.
IGMP Overview
The SSR 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 SSR, 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.
IGMP allows per-interface control of the host query interval and response time. Query
interval defines the time between IGMP queries. Response time defines the time the
SSR will wait for host responses to IGMP queries.
DVMRP Overview
DVMRP is an IP multicast routing protocol. On the SSR, DVMRP routing is imple-
mented as specified in the draft-ietf-idmr-dvmrp-v3-06.txt file, which is an Internet
Engineering Task Force (IETF) document. The SSR’s implementation of DVMRP
supports the following:
• mtrace, which is a utility that tracks the multicast path from a source to a receiver.
• Generation identifiers, which are assigned to DVMRP whenever that protocol is
started on a router.