Cabletron Systems Fast Network 10, User Manual

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Chapter 1: Introduction
Page 1-8 Fast Network 10 User Guide
forwards the packet to the network segment associated with that
destination address. However, if the packet’s source and destination
address are on the same network segment, known as
local traffic , the
packet is automatically discarded (i.e., ignored by the FN10).
For example, a file transmitted from Workstation A to Workstation C in
Figure 1-4 does not need to leave LAN 1. The FN10 connected to LANs 1
and 2 sees all traffic from LAN 1, including LAN 1 local traffic.
Figure 1-4 Typical Switching Application
By forwarding only packets addressed to devices on other network
segments, the FN10 reduces unnecessary traffic and thereby enhances the
overall performance of the network.
1.5.1.3 Spanning Tree Algorithm
The FN10 supports the IEEE 802.1d Spanning Tree algorithm. The
Spanning Tree algorithm converts multiple LANs into a “spanning tree”
of networks. It is used to prevent bridging loops. This standard defines a
logical (not physical) network configuration consisting of one extended
LAN without active duplicate paths between spanning tree bridges.
The FN10, along with other IEEE 802.1d Spanning Tree compliant
bridges in the network, dynamically configure the network topology into
a single Spanning Tree by exchanging Bridge Protocol Data Units
(BPDUs). Typically, each LAN segment is sent one BPDU every two
seconds.
When there are multiple FN10s connecting LANs in a loop, the Spanning
Tree algorithm determines which FN10 should forward packets to the
LAN. If there is a cable break or a port failure, the network topology is
LAN 1
LAN 2
A B C
FastNet 10
FN10