Information Technology Reference
In-Depth Information
20
CHAPTER
Troubleshooting Transparent Bridging
Environments
Transparent bridges were first developed at Digital Equipment Corporation (Digital) in the early 1980s
and are now very popular in Ethernet/IEEE 802.3 networks.
This chapter first defines a transparent bridge as a learning bridge that implements a Spanning Tree.
A deeper description of the Spanning-Tree Protocol is included.
•
Cisco devices implementing transparent bridging previously were split in two categories: routers
running IOS, and the Catalyst range of switches, running specific software. This is not the case
anymore, however, because several Catalyst products are now based on the IOS. This chapter
introduces the different bridging techniques available on IOS devices. For Catalyst software specific
configuration and troubleshooting, refer to Chapter 23, “Troubleshooting ATM LAN
Environments.”
•
Finally, this chapter introduces some troubleshooting steps classified by symptoms of potential
problems that typically occur in network implementations featuring transparent bridging.
•
Transparent Bridging Technology Basics
Transparent bridges are so named because their presence and operation are transparent to network hosts.
When transparent bridges are powered on, they learn the network's topology by analyzing the source
address of incoming frames from all attached networks. For example, if a bridge sees a frame arrive on
line 1 from Host A, the bridge concludes that Host A can be reached through the network connected to
line 1. Through this process, transparent bridges build a table such as the one in Table 20-1.
Table20-1 A Transparent Bridging Table
Host Address
Network Number
0000.0000.0001
1
0000.b07e.ee0e
7
. . .
0050.50e1.9b80
4
0060.b0d9.2e3d
2
0000.0c8c.7088
1
. . .
