User's Manual Part 1

68 APCD-LM043-8.0 (DRAFT C)
4: IP Network Planning
4.6 Comparison of Modes
Routed Mode
Switched Ethernet and
Through Only Modes
Ethernet Broadcast
Domain
Each radio network is a separate
domain. The Ethernet network is a
separate domain.
The Radio networks and Ethernet
networks are in the same domain,
so all Ethernet devices up to the
nearest router port share the
domain.
Number of Ethernet
Devices.
Recommend less than 650 per
radio network and less than 650 on
the Ethernet network. (The Ethernet
network is likely to be capacity
limited).
Recommend less than 650 total
devices including the Ethernet
network per router port. With
multiple CCUs, v4.0 bridge table
size imposes further limits. See
Network Size Guidelines on page
65.
Radio Network
Broadcasts
ARPs generated by EUMs and
subscribers appear only on the
radio network.
IP subnet broadcast packets from
outside the network are broadcast
on the radio network unless they
are blocked, either at the CCU or
the gateway router.
Other Ethernet broadcast packets
are broadcast to the radio network
ARPs generated by EUMs and
subscribers and all packets to
unknown Ethernet MAC addresses
are broadcast over all radio
networks and the Ethernet network.
Each CCU learns about MAC
addresses over time, so packets
with unknown Ethernet MAC
addresses will be rare.
IP subnet broadcast packets from
outside the network are broadcast
over all radio networks and the
Ethernet network unless they are
blocked at the gateway router.
Other Ethernet broadcast packets
are broadcast over all radio
networks and the Ethernet network.
Multicast Traffic Ethernet multicast packets are not
passed between the CCU Ethernet
network and radio network.
CCU does not support or route IP
multicast packets.
Ethernet multicast packets sourced
on the radio network will be treated
as an Ethernet broadcast packet.
Ethernet multicast packets will be
passed between CCU Ethernet
network and radio network,
appearing as broadcast traffic on
the radio network.
CCU Ethernet Port
Mode
Directed. Only broadcast packets
and Ethernet packets directed to the
CCU are received at the Ethernet
interface.
Promiscuous. Every packet seen on
the Ethernet port is read and
checked. If the Ethernet network
has excessive traffic, this can
degrade the CCU’s performance.