Bridging

2.Type in the new Ageing Time (allowable range is 10 to 1,000,000 seconds; the default is 300 seconds).

3.Click to accept the new Ageing Time, or click to exit the window without making changes.

NOTE

Note that the Source Addresses Ageing Time is the same as the Ageing Time displayed (and configured) via the Filtering Database window; setting the Ageing Time in the Source Addresses window also changes the time in the Filtering Database window, and vice versa.

Bridge Spanning Tree

The Bridge Spanning Tree window allows you to display and modify the selected module’s bridge port information and protocol parameters relating to the Spanning Tree Algorithm.

In a network design with multiple bridges placed in parallel (i.e., attached to the same LAN), data loops must be prevented. The Spanning Tree Algorithm (STA) is the method that bridges use to communicate with each other to ensure that only a single data route exists between any two end stations. On a LAN interconnected by multiple bridges, Spanning Tree selects a controlling Root Bridge and Port for the entire bridged LAN, and a Designated Bridge and Port for each individual LAN segment. A Designated Port/Bridge for a LAN segment forwards frames from that LAN towards the Root Bridge, or from the Root Bridge onto the LAN. All other bridge ports attached to that LAN are configured to filter (block) frames. When data passes from one end station to another across a bridged LAN, it is forwarded through the Designated Bridge/Port for each LAN segment towards the Root Bridge, which in turn forwards frames towards Designated Bridges/Ports on its opposite side.

During the Root Bridge Selection process, all bridges on the network communicate STA information via Bridge Protocol Data Units (BPDUs). With BPDUs, all network bridges collectively determine the current network topology and communicate with each other to ensure that the topology information is kept current.

To access the Bridge Spanning Tree window:

1.From the Bridge Status window, click on to display the Bridge menu. or

From the Module View window, click on the Bridge label in the module display; the bridge menu will appear.

2.Drag down to Spanning Tree..., and release. The Bridge Spanning Tree window, Figure 5-9, will appear.

5-14

Bridge Spanning Tree

Page 67
Image 67
Cabletron Systems 9A128-01 manual Bridge Spanning Tree