User`s guide

1-1
Chapter 1
Introduction
Traditional 802.1D Spanning Tree Bridges only allow one active data path
between any two switches; all other parallel data paths are in Standby or Blocking
mode. If one interface or path should fail, then the other interface automatically
comes out of Blocking mode and forwards all of the trafÞc. This is Þne for
redundancy purposes. However, it is not the most efÞcient use of resources.
SmartTrunk, also referred to as SmartTrunking, is Cabletron SystemsÕ
terminology for load balancing or load sharing. SmartTrunk provides the ability
to take full advantage of the networkÕs redundant bandwidth. SmartTrunk
divides network trafÞc across multiple ports in parallel to provide additional
throughput. The SmartTrunk application can be used with any of DigitalÕs
MultiSwitch 700 switch modules (except ATM modules).
SmartTrunking
A physical port conÞgured in a SmartTrunk Group must:
¥ Be connected in a point-to-point link (full-duplex is recommended)
¥ Be connected to a port that is also conÞgured as part of a SmartTrunk Group
¥ Have Spanning Tree protocol enabled
Whenever a physical port is conÞgured in a SmartTrunk Group, the port will send
proprietary protocol messages (see PLAP and LLAP information in the
Compatibility section). Once the two switches at opposite ends of the link agree
that the trunking state is enabled, the SmartTrunk Group is established. As
additional ports are identiÞed as belonging to the same SmartTrunk Group, the
SmartTrunk Group is automatically reconÞgured to take advantage of the
additional paths.