Administrator 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 in the Dell EMC Networking OS is redirected using the MAC address, and multicast control
traffic and multicast data traffic might map to the same MAC address, the Dell EMC Networking OS might forward data traffic
with certain MAC addresses to the CPU in addition to control traffic.
As the upper five bits of an IP Multicast address are dropped in the translation, 32 different multicast group IDs 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 and 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
NTP 01:00:5e:00:01:01
VRRP 01:00:5e:00:00:12
PIM-SM 01:00:5e:00:00:0d
● The Dell EMC Networking OS implementation of MTRACE is in accordance with IETF draft draft-fenner-traceroute-ipm.
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