Internetworking and Management Overview

MAC-LEVEL BRIDGING AND SPANNING TREE PROTOCOL

The following sections describe the MAC-level bridge and the Spanning Tree algorithm function.

MAC-Level Bridging

A bridge moves information across an internetwork from a source to a destination at the link layer (of an OSI reference model). The information is sent to a physical address known as a Media Access Control (MAC) address.

The Campus-REX provides transparent Ethernet MAC-level bridging. It is a completely self-contained bridge with a CPU, memory subsystems (RAM, Flash, etc.), an Ethernet controller and Ethernet drivers, and other glue logic. It provides complete main bridging tasks of learning, forwarding, filtering, and hashing/buffer management. Additionally, it offers 802.1d Spanning Tree protocol, packet encapsulation (through HDLC or PPP framing), and other local tasks.

Forwarding performance is at a full serial line rate and filtering performance is at a full Ethernet rate of 14 kpps for 64-byte frames (minimum size).

Spanning Tree

Spanning Tree protocol creates a logical topology to overlay a physical network. This overlay disables all loops in the data path. Enabling Spanning Tree ensures a unique, primary path from any node on a network to any other node. Also, if the primary path is lost, Spanning Tree creates a new primary path by enabling links in the physical network that were previously disabled in creating the active topology. The following figure shows an example of Spanning Tree.

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Campus-REX RS Interface Card User Manual