FDDINetwork Topologies 79
7
Mixed FDDI/Ethernet Networks
This section concentrates on the implementation of mixed FDDI/Ethernet
networks. The same principles could be applied to mixed FDDI/802.3 and
mixed FDDI/802.5 (TokenRing) networks. FDDI and Token Ring networks are
based on a ring topology; Ethernet and 802.3 networks are based on a bus
topology.

FDDI/Ethernet IP Router

The machines at the boundaries between the FDDI and Ethernet networks in
the following examples are assumed to be Ultra systems that have at least one
SunFDDI/P interface and one Ethernet interface installed. These machines
operate as IP routers.
Special software is not required. The combination of the SunFDDI/P driver
and the SunOS IP routing implementation handles the routing and relayingof
packets between FDDI and Ethernet stations. Note that the packets on the
FDDI ring can be as long a 4500 octets, whereas Ethernet packets are restricted
to a maximum of 1500 octets.
Figure7-7 illustrates the basic topology of a mixed FDDI/Ethernet network.
In this example, there are two FDDI/Ethernet IP routers that representthe
boundaries between the three networks.