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Group Settings
Parameter
Description
MVR VLAN Select a MVR VLAN.
Group Name Configures the group name.
Start Address Configures the multicast start address.
Quantity
Configures the quantity of the multicast address.
6.2.5.
Multicast Address
6.2.5.1.
Introduction
A multicast address is associated with a group of interested receivers. According to RFC 3171,
addresses 224.0.0.0 to 239.255.255.255, the former Class D addresses, are designated as
multicast addresses in IPv4.
The IANA owns the OUI MAC address 01:00:5e, therefore multicast packets are delivered by
using the Ethernet MAC address range 01:00:5e:00:00:00 - 01:00:5e:7f:ff:ff. This is 23 bits of
available address space.
The first octet (01) includes the broadcast/multicast bit. The lower 23 bits of the 28-bit multicast
IP address are mapped into the 23 bits of available Ethernet address space. This means that there
is ambiguity in delivering packets. If two hosts on the same subnet each subscribe to a different
multicast group whose address differs only in the first 5 bits, Ethernet packets for both multicast
groups will be delivered to both hosts, requiring the network software in the hosts to discard the
unrequired packets.
