Cabletron Systems SmartSwitch 8-slot, Руководство пользователя

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Chapter 2
Chapter 2 Bridging Configuration Guide
Bridging Overview
The SmartSwitch Router provides the following bridging functions:
• Complies with the IEEE 802.1d standard
• Complies with the IGMP multicast bridging standard
• Provides wire-speed address-based bridging or flow-based bridging
• Provides the ability to logically segment a transparently bridged network into virtual
local-area networks (VLANs) based on physical ports or protocol (IP or IPX or
bridged protocols like Appletalk)
• Allows frame filtering based on MAC address for bridged and multicast traffic
• Provides integrated routing and bridging, which supports bridging of intra-VLAN
traffic and routing of inter-VLAN traffic
Spanning Tree (IEEE 802.1d)
Spanning tree (IEEE 802.1d) allows bridges to dynamically discover a subset of the
topology that is loop-free. In addition, the loop-free tree that is discovered contains
paths to every LAN segment.
Bridging Modes (Flow-Based and Address-Based)
The SSR provides the following types of wire-speed bridging:
Address-based bridging - The SSR performs this type of bridging by looking up the
destination address in an L2 lookup table on the line card that receives the bridge
packet from the network. The L2 lookup table indicates the exit port(s) for the bridged
packet. If the packet is addressed to the SSR's own MAC address, the packet is routed
rather than bridged.
Flow-based bridging - The SSR performs this type of bridging by looking up an entry
in the L2 lookup table containing both the source and destination addresses of the
received packet in order to determine how the packet is to be handled.
The SSR ports perform address-based bridging by default but can be configured to
perform flow-based bridging instead, on a per-port basis. A port cannot be configured
to perform both types of bridging at the same time.
The SSR performance is equivalent when performing flow-based bridging or address-
based bridging. However, address-based bridging is more efficient because it requires