White Papers

Multicast Features
Dell Networking OS supports multicast features.
The Dell Networking OS supports the following multicast protocols:
● PIM Sparse-Mode (PIM-SM)
● PIM Source-Specific Mode (PIM-SSM)
● Internet Group Management Protocol (IGMP)
● Multicast Source Discovery Protocol (MSDP)
Topics:
• Enabling IP Multicast
• Implementation Information
• First Packet Forwarding for Lossless Multicast
• Multicast Policies
• IPv4 Multicast Policies
• Understanding Multicast Traceroute (mtrace)
• Printing Multicast Traceroute (mtrace) Paths
• Supported Error Codes
• mtrace Scenarios
Enabling IP Multicast
Prior to enabling any multicast protocols, you must enable multicast routing.
● Enable multicast routing.
CONFIGURATION mode
ip multicast-routing
Implementation Information
Because protocol control traffic in the 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 Networking OS might forward data traffic with certain MAC
addresses to the CPU in addition to control traffic.
As the upper 5 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
NTP 01:00:5e:00:01:01
VRRP 01:00:5e:00:00:12
37
Multicast Features 503