Operation Manual – Multicast Protocol
H3C S3610&S5510 Series Ethernet Switches
Chapter 1 Multicast Overview
1-10
Figure 1-5
IPv4-to-MAC address mapping
The high-order four bits of a multicast IPv4 address are 1110, indicating that this
address is a multicast address, and only 23 bits of the remaining 28 bits are mapped to
a MAC address, so five bits of the multicast IPv4 address are lost. As a result, 32
multicast IPv4 addresses map to the same MAC address. Therefore, in Layer 2
multicast forwarding, a device may receive some multicast data addressed for other
IPv4 multicast groups, and such redundant data needs to be filtered by the upper layer.
2)
IPv6 multicast MAC addresses
The high-order 16 bits of an IPv6 multicast MAC address are 0x3333, and the low-order
32 bits are the low-order 32 bits of a multicast IPv6 address.
shows an
example of mapping an IPv6 multicast address, FF1E::F30E:0101, to a MAC address.
Figure 1-6
An example of IPv6-to-MAC address mapping
