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19
CONFIGURING BRIDGE
This chapter contains information on the following topics:
■ Bridge Overview
■ Configure Bridge’s Routing Function
■ Display and Debug Bridge
■ Typical Bridge Configuration
Bridge Overview 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 in the networks widely dispersed, using 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 networks 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 the
communication in mixed Toke Ring and Ethernet environments.
The transparent bridging supported by the 3Com Router series has the following
features:
■ Conforms to the IEEE 802.1d standards and supports the STP and bridging
functions specified in IEEE 802.1d.
■ Supports bridging on the links of PPP and HDLC.
■ Supports bridging on X.25 links.