3Com 10014299 Bridge Overview, Configure Bridge’s Routing Function, Display and Debug Bridge

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.