Cabletron Systems ELS10-26TX User Manual

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Introduction
1-9
 
By forwarding only packets addressed to devices on other network 
segments, the SmartSTACK 10 ELS10-26 reduces unnecessary 
traffic and thereby enhances the overall performance of the 
network.
 
Note:
 
If the packet address is not found in the Bridge Address Table, it 
will be forwarded (flooded) to all network segments.
 
Spanning Tree  Algorithm
 
The SmartSTACK 10 ELS10-26 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 SmartSTACK 10 ELS10-26, 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 (this is the 
default setting).
When there are multiple SmartSTACK 10 ELS10-26s connecting 
LANs in a loop, the Spanning Tree algorithm determines which 
SmartSTACK 10 ELS10-26 should forward packets to the LAN. If 
there is a cable break or a port failure, the network topology is 
automatically reconfigured by the Spanning Tree protocol to create 
an alternate path to the LAN.
 
1.5.2  SmartSTACK 10 ELS10-26 Bridge Address Table
 
The SmartSTACK 10 ELS10-26 creates and maintains a dynamic 
database of addresses called the Bridge Address Table. The 
SmartSTACK 10 ELS10-26 examines every packet to determine its 
source address and LAN segment origin. It then compares the 
source address and segment information it finds to the entries in 
the Bridge Address Table.