Chapter 3 Bridge Configuration; Introduction To Bridge; Main Functions Of Bridging - 3Com 3C13636 Configuration Manual

3Com Router 3000 Ethernet Family
Configuration Guide

Chapter 3 Bridge Configuration

3.1 Introduction to Bridge

Bridge is a type of network device on the data link layer, which interconnects Local
Area Networks (LANs) and transfers data between them. In some small-sized
networks, especially those widely dispersed networks, the employment of bridges can
reduce the network maintenance cost, and the network terminal users do not need to
make special settings for the devices, since the bridges interconnect networks just
like hubs.
In practice, there are four types of bridging:
Transparent Bridging: Such bridging is used to interconnect LANs of the same
medium. It is mainly applied in the Ethernet environment. Usually, transparent
bridging keeps a bridging table that records the correlation between destination
MAC addresses and interfaces.
Source-route Bridging: Such bridging forwards frames based on the routing
indicators contained in the frames. The table of correlation between destination
MAC addresses and routing indicators will be determined and maintained by the
end stations (the starting and the ending point). This bridging is found primarily in
the Token Ring environments.
Translational Bridging: Such bridging is used to interconnect LANs of different
physical media. It is typically applied to interconnect different types of networks,
such as Ethernet, Fiber Distributed Data Interface (FDDI) and Token Ring.
Source-route Translational Bridging: As the name implies, such bridging is the
hybrid of "Source-route Bridging" and "Translational Bridging". They allow of the
communication between devices in mixed Toke Ring and Ethernet environments.
The router supports transparent bridging function, supporting:
Bridging on PPP and HDLC links
Bridging on X.25 links
Bridging on ATM
Bridging on VLAN sub-interfaces
Bridging on dial interface
Both routing and bridging
Command configuration and management
Logging, trapping and debugging

3.1.1 Main Functions of Bridging

The following covers the overall functions of bridging.
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Chapter 3 Bridge Configuration