Administrator Guide

Figure 80. Multicast with ECMP
Implementation Information
Because protocol control traffic in Dell Networking OS is redirected using the MAC address, and multicast control traffic and
multicast data traffic might map to the same MAC address, Dell Networking OS 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
NTP 01:00:5e:00:01:01
VRRP 01:00:5e:00:00:12
PIM-SM 01:00:5e:00:00:0d
● The Dell Networking OS implementation of MTRACE is in accordance with IETF draft draft-fenner-traceroute-ipm.
● Multicast is not supported on secondary IP addresses.
● Egress L3 ACL is not applied to multicast data traffic if you enable multicast routing.
Multicast Features
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