Multicast Features | 665Implementation Information• Because protocol control traffic in FTOS is redirected using the MAC address, and multicast controltraffic and multicast data traffic might map to the same MAC address, FTOS might forward data trafficwith 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 multicastgroup IDs all map to the same Ethernet address. For example, 224.0.0.5 is a well known IP address forOSPF that maps to the multicast MAC address 01:00:5e:00:00:05. However, 225.0.0.5, 226.0.0.5, etc.,map to the same multicast MAC address. The Layer 2 FIB alone cannot differentiate multicast controltraffic 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 onesbelow.• The FTOS 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 multicast routing is enabled.Multicast PoliciesFTOS offers parallel Multicast features for IPv4 and IPv6.• IPv4 Multicast Policies on page 665• IPv6 Multicast Policies on page 673IPv4 Multicast Policies• Limit the Number of Multicast Routes on page 666• Prevent a Host from Joining a Group on page 667• Rate Limit IGMP Join Requests on page 669• Prevent a PIM Router from Forming an Adjacency on page 669• Prevent a Source from Registering with the RP on page 669• Prevent a PIM Router from Processing a Join on page 670• Using a Static Multicast MAC Address on page 671Protocol Ethernet AddressOSPF 01:00:5e:00:00:0501:00:5e:00:00:06RIP 01:00:5e:00:00:09NTP 01:00:5e:00:01:01VRRP 01:00:5e:00:00:12PIM-SM 01:00:5e:00:00:0d
