Users Guide

Multicast Features

The Dell Networking OS supports the following multicast protocols:

• PIM Sparse-Mode (PIM-SM)

• Internet Group Management Protocol (IGMP)

• Multicast Source Discovery Protocol (MSDP)

Topics:

• Enabling IP Multicast

• Implementation Information

• First Packet Forwarding for Lossless Multicast

• Multicast Policies

• Understanding Multicast Traceroute (mtrace)

• Printing Multicast Traceroute (mtrace) Paths

• Supported Error Codes

• mtrace Scenarios

Enabling IP Multicast

Before enabling any multicast protocols, you must enable IP multicast routing.

• Enable multicast routing.

CONFIGURATION mode

ip multicast-routing

Implementation Information

Because protocol control traffic is redirected using the MAC address, and multicast control traffic and multicast data traffic might map to

the same MAC address, the system might forward data traffic with certain MAC addresses to the CPU in addition to control traffic.

As the upper5 bits of an IP Multicast address are dropped in the translation, 32 different multicast group IDs all map to the same Ethernet

address. For example, 224.0.0.5 is a known IP address for open shortest path first (OSPF) that maps to the multicast MAC address

01:00:5e:00:00:05. However, 225.0.0.5, 226.0.0.5, and so on, map to the same multicast MAC address. The Layer 2 forwarding

information base (FIB) alone cannot differentiate multicast control traffic multicast data traffic with the same address, so if you use IP

address 225.0.0.5 for data traffic, both the multicast data and OSPF control traffic match the same entry and are forwarded to the CPU.

Therefore, do not use well-known protocol multicast addresses for data transmission, such as the following.

Protocol

Ethernet Address

OSPF

01:00:5e:00:00:05

01:00:5e:00:00:06

RIP 01:00:5e:00:00:09

Multicast Features 625