Accton Technology ES4710BD manual IP Multicast Packets Forwarding

ES4710BD 10 Slots L2/L3/L4 Chassis Switch

group at any time.

A multicast group can be either a perpetual one or temporary one. Part of multicast addresses are assigned officially and referred to as the perpetual multicast group. The IP address of a perpetual multicast group remains the same, but the membership can be changed. A perpetual multicast group can have any number of members, even zero. IP multicast addresses not reserved for perpetual multicast group can be used by temporary multicast groups.

224.0.0.0– 224.0.0.255 are reserved multicast addresses (perpetual group address), the address

224.0.0.0is not used, the other addresses are available for routing protocols; 224.0.1.0 – 238.255.255.255 are multicast addresses available to users (temporary group address), and is valid for the whole network; 239.0.0.0 – 239.255.255.255 are local administrative multicast address and is valid for specific local ranges. The following is a list for common reserved multicast addresses:

224.0.0.0Base address (reserved)

224.0.0.1All-host address

224.0.0.2All-multicast-router address

224.0.0.3Not for allocation

224.0.0.4DVMRP router

224.0.0.5OSPF router

224.0.0.6OSPF DR

224.0.0.7ST router

224.0.0.7ST host

224.0.0.9RIP-II router

224.0.0.10IGRP router

224.0.0.11Active proxy

224.0.0.12DHCP Server/Relay proxy

224.0.0.13All PIM routers

224.0.0.14RSVP packaging

224.0.0.15All CBT routers

224.0.0.16Specified SBM

224.0.0.17All SBMS

224.0.0.18VRRP

When transferring unicast IP packets on Ethernet, the destination MAC address is the MAC of the receiver. However, in transferring multicast packets, as the destination is no longer one specific recipient but a group with unknown members, the destination address used is the multicast MAC address. Multicast MAC address is corresponding 5 to the multicast IP address. According to IANA (Internet Assigned Number Authority), the 24 MSbs of multicast MAC is 0x01005e and 23 LSbs of multicast MAC is the same of the multicast IP address.

As only 23 bits out of the 28 LSbs of multicast IP address are mapped to MAC address, for one MAC address there will be 32 corresponding multicast IP addresses.

19.1.3 IP Multicast Packets Forwarding

In the multicast model, the source host sends information to the host group represented by the

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