3Com Baseline 2816 User Manual

Also see for 3CBLUG16A - Baseline Switch 2816: User guide User guide

Contents

3Com Baseline 2816 User Manual Manual pdf 45 page image

Using the System Tools 45lost while the new software is being copied to theSwitch).The upgrade procedure can take a few minutes, and iscomplete when the Power LED has stopped flashing andis permanently green. Make sure that you do not inter-rupt power to the Switch during the upgrade proce-dure; if you do, the software may be corrupted and theSwitch may not start up properly afterwards. If thePower LED continues to flash after a failed upgrade,refer to “Troubleshooting” on page 49.Spanning TreeThis administrative tool supports the configuration ofthe Switch to forward, or block and discard 802.1Dspanning tree BPDU packets.Spanning tree is a bridge-based system for providingfault tolerance on networks and can be used to detectand disable network loops. The spanning tree ensuresthat the optimal path is maintained between spanningtree-compliant networked devices by:■ Disabling redundant paths when the main paths areoperational.■ Enabling redundant paths if the main paths fail.Spanning tree uses a distributed algorithm to select abridging device that serves as the root of the spanningtree network. The bridging device known as the RootBridge generates BPDUs (Bridge Protocol Data Units) onall ports at a regular interval known as the Hello Time.All other spanning tree-compliant devices on thenetwork have a designated Root Port. This is the Portnearest the Root Bridge and it is used for receiving theBPDUs initiated by the Root Bridge. If a bridge does notget a Hello BPDU after a predetermined interval, thebridge assumes that the link to the Root Bridge is down.This bridge will then initiate negotiations with otherbridges to reconfigure the network to reestablish a validnetwork topology.After all the bridges on the network have determinedthe configuration of their ports, each bridge onlyforwards traffic between the Root Port and the portsthat are the Designated Bridge Ports for each networksegment. All other ports are blocked, which means thatthey are prevented from forwarding traffic.