Introduction
packets to the LAN. If there is a cable break or a port failure, the network topology is automatically reconfigured by the Spanning Tree protocol to create an alternate path to the LAN.
1.5.2SmartSTACK 100 ELS100-16TX Bridge Address Table
The SmartSTACK 100 ELS100-16TX creates and maintains a dynamic database of addresses called the Bridge Address Table. The SmartSTACK 100 ELS100-16TX examines every packet to determine its source address and LAN segment origin. It then compares the source address and segment information it finds to the entries in the Bridge Address Table.
If a packet’s address is not already stored in the Bridge Address Table, the SmartSTACK 100 ELS100-16TX adds the learned address, associated segment number, and a timer value indicating the age of the observation. Consequently, the SmartSTACK 100 ELS100-16TX knows the address and associated segment number the next time it sees that address. By using the information stored in the Bridge Address Table, the SmartSTACK 100 ELS100-16TX is able to quickly forward each packet to the correct LAN segment.
The SmartSTACK 100 ELS100-16TX learns addresses from all packets, including data transmissions and “keep alive” packets (packets sent by an idle station to let other stations know it is present and functional). When devices are added to the network, removed from it, or relocated, you do not have to reconfigure the SmartSTACK 100 ELS100-16TX. The unit automatically learns new device addresses, recognizes when a previously used address is missing, or when a device has been moved to a new LAN segment.
An address stored in the Bridge Address Table is discarded if there is no subsequent activity from that address after a configured length of time (five minutes by default). This aging process ensures that the Bridge Address Table is continually updated.
Addresses are continually added to and deleted from the Bridge Address Table, reflecting the dynamic nature of internetwork traffic.
