Fast EtherHub 3500 System User’s Guide
Product Overview 1-9
Data Switching with the SmartExtender Modules

Switching Technology

The SmartExtender Modules that plug into the expansion slot
on the front panel of the Fast Ethernet 3500 series use advanced
switching techniques to provide a high-speed network
backbone. Each extender module acts as a two-port Ethernet
switch which effectively partitions the stack from the backbone.
The module scans the destination address from the packet
header, searches the routing table provided for the incoming
port and forwards the packet only if required, often before fully
received. A learning function stores the address and corre-
sponding segment identifier of each incoming and outgoing
packet in a routing table. This information is subsequently
used to filter packets whose destination address is on the same
segment as the source address. This confines network traffic to
its respective domain, reducing the overall load on the network.

Configuration Options for the SmartExtender Modules

Only the 100BASE-TX and
100BASE-FX media support
full-duplex operation.
The SmartExtender Modules can be connected to either a
subnetwork, or directly to a server or key workstation. In
addition to partitioning an overloaded network, they provide a
connection between legacy 10BASE-T networks and the newer
generation 100BASE-TX, and can be configured to operate in
either full-duplex or half-duplex data transfer mode to support
the interconnection requirements of other high-speed devices.
These modules perform adaptive cut-through switching,
which is capable of instantly forwarding or filtering a packet
according to the destination address scanned from the packet
header. This technique transmits packets with near-zero latency.