System Settings 285
Multicast Addresses The NBX system uses IP multicast addressing to distribute information for
these system features:
■Mapped line appearances
■Music on hold
■Internal page
■External page
■Conference calls
These features are available on Layer 2 and Layer 3 IP devices. The
IP implementation uses Internet Group Management Protocol (IGMP)
to transmit and distribute the necessary data and audio.
If you configure your NBX system to use IP On-the-Fly or Standard IP and
your switches use IGMP Snooping, you must have an IGMP Host on the
network. Typically, an IGMP Host is an IP Multicast Router or a switch that
has IGMP Query capability.
The NBX system IGMP is an implementation of administratively scoped
IP multicast that uses three scopes of administration:
■Local scope — Limited by local routers with IP addresses 239.255.0.0
through 239.255.0.16
■Organizational local scope — Limited by boundary routers with
IP addresses 239.192.0.0 through 239.192.0.14
■Global scope — IP addresses 224.2.0.0 through 224.2.127.253
IGMP may not be available in all systems or network topologies. All of the
routers between the various components must support IGMP and the
necessary router protocols to establish a path for the IP multicast packets.
Each event that occurs in an IGMP setup, such as taking a telephone off
the hook, causes a packet of 200 Kb to 300 Kb to be sent.
The default settings for the IP multicast addresses should work in most
network environments. Certain addresses are reserved.
The MAC address and the IP address displayed on any one line of the
Multicast Address List window are not related.