INTRODUCTION

This feature is referred to as Aging Time. Aging Time can be altered through Cabletron Systems’ Remote LANVIEW Network Control Management for the Cabletron Systems' NB20E and NB25E.

1.5MULTIPLE BRIDGE ENVIRONMENTS

Both the NB20E and NB25E Two Port Bridges are designed to promote maximum network use in multiple bridge environments. A bridge learns the bridge topology of its network from bridge protocol data that is transmitted onto the network by each bridge. The bridges then apply a Spanning Tree Algorithm to select a root bridge and to determine primary data paths within potential data loop configurations. A Spanning Tree Algorithm, as defined earlier, is a hierarchy (or tree) of priorities that is established between bridges. This hierarchy guarantees that primary and redundant data paths will be clearly defined at all times, so that the network is available to users at all times.

1.5.1The Root Bridge

One bridge in the network is established as the root bridge. This bridge has priority over all other bridges. Each bridge in a Spanning Tree must learn which bridge is the root and then determine its own relative priority within the network.

Determining the root bridge begins with the broadcast of Bridge Protocol Data Units (BPDUs) across the network. When the bridges go on line, each bridge sends out a BPDU which contains its priority field and its unique identifier or Ethernet address. Through the broadcast of these identifiers across the network, the bridges learn which bridge has the highest priority, or lowest identifier. This bridge becomes the root bridge for the network. Each bridge then determines its own priority in relation to this bridge.

The network manager can, however, override this process for determining the root. Using the root switch, the manager can manually select a different bridge to be the root by applying a selectable switch at the appropriate bridge. This bridge transmits BPDUs to inform the other bridges that it is now the root. With this information, the bridges immediately learn their new priority in relation to the new root, and the system of priorities is maintained.

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Cabletron Systems NB25 E, NB20E user manual Multiple Bridge Environments, Root Bridge
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NB25 E, NB20E specifications

Cabletron Systems, renowned for its innovative networking solutions in the late 20th century, introduced the NB20E and NB25E series, which made a significant impact in the realm of network management and reliability. These devices were tailored for businesses seeking to enhance their network infrastructure with efficiency and reliability.

The NB20E is known for its robust performance in medium-sized network environments. It operates with an architecture that allows for seamless integration into existing networks, providing essential features that cater to both versatility and scalability. One of its standout functionalities is the support for multiple protocols, enabling organizations to harness various networking standards without the need for extensive alterations to their current setups.

On the other hand, the NB25E extends these capabilities further, offering enhanced throughput and a more comprehensive range of networking options. This makes it particularly suitable for larger businesses with growing networking demands. The utilization of advanced technologies, such as its embedded intelligence, ensures that the NB25E can efficiently manage and direct network traffic, thus minimizing latency and maintaining optimal performance even during peak usage times.

Both models provide essential characteristics such as a modular design, allowing for easy upgrades and maintenance. This modularity not only prolongs the lifespan of the devices but also provides flexibility for future expansions or modifications as business needs evolve. The systems support various interfaces, catering to diverse environments and ensuring easy connectivity to other networking equipment.

Security is a paramount concern in today’s interconnected world, and Cabletron Systems addressed this in the NB20E and NB25E series. The devices are equipped with advanced security features that protect against unauthorized access and ensure data integrity, providing peace of mind for organizations relying on critical data transmissions.

In addition to their technical advantages, both models offer user-friendly management software, making monitoring and control straightforward even for those with limited networking expertise. This ease of use ensures that companies can leverage their investment fully without requiring extensive training or resources.

In summary, the Cabletron Systems NB20E and NB25E series represent a significant leap in networking technology during their era. With advanced features, modular capabilities, and a commitment to security, these devices remain a noteworthy consideration for businesses looking to enhance their networks and prepare for future growth.
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